Silages of Native Switchgrass and Gamagrass: Fermentation Characteristics, Nutritive Value, and Quality

The research reported in this publication was funded by the North Carolina Agricultural Research Service (NCARS) and by the United States Department of Agricultural, Agricultural Research Service (USDA-ARS), as part of a joint forage-animal research program. Mention of trade name, proprietary products, or specific equipment does not constitute a guarantee or warranty by either NCARS or USDA-ARS and does not imply its approval to the exclusion of other products that may be suitable.

Cover photographs courtesy of the NCARS and USDA–ARS.

Abstract

This bulletin publishes the results of eight experiments that addressed aspects of nutritive value (laboratory estimates of in vitro dry matter disappearance and chemical composition) and quality (animal responses) of perennial warm-season forages preserved as hay, baleage, and silage. Although each experiment was conducted independently, those pertaining to switchgrass and those pertaining to gamagrass have been grouped and appear under Section I and Section II, respectively. Our focus in this bulletin is on the ensiling potential of these two native, perennial, warm-season grasses.

Our purpose in publishing this bulletin is to summarize original research data, with associated methodology, for future reference. We have included a brief Results and Discussion section for each experiment, followed by a Summary and Conclusions section of the major findings. Consequently, the interested reader is directed to the Summary and Conclusions section at the end of each experiment for an assessment of the findings that is not reiterated elsewhere.

Introduction

In animal production systems of the Upper South, the preservation of forage for later consumption is essential to guard against forage shortages. Shortages may occur during periods of extreme summer drought and during the winter cold period (January through March). The climate of the Upper South is suitable for the growth and production of warm-season grasses. However, the preservation of superior yielding forages as hay, without rain damage, is difficult in the region because of excessive humidity and the frequency of summer afternoon thunderstorms. The more productive forages with heavy stems may require excessive time to field cure prior to baling. This prolonged exposure increases the probability of rain damage and warrants we consider preserving these perennial coarse grasses as silage—either direct-cut or wilted and ensiled—instead of hay.

Two perennial, native, warm-season grasses that warrant further consideration are switch-grass (Panicum virgatum L.) and eastern gamagrass (Tripsacum dactyloides L.). Both have shown potential as forage for pasturage or when conserved as hay.

Switchgrass, consisting of lowland and upland types, is well adapted to the Upper South. The lowland types are most productive in the region, whereas the upland types are more productive farther north. Switchgrass is a multipurpose, perennial, warm-season grass that can be used for pasture, conserved as hay, or used as a biomass source. Initial growth of the lowland switchgrass cultivars is very robust with heavy stems and broad leaves. The regrowth, however, is generally finer in stem with more narrow leaves. Further, physiological development of the regrowth is rapid and moves from vegetative to heading much quicker than noted in the initial growth. Conservation of the initial growth of lowland switchgrass as hay, however, has excessive risk of rain damage due to the growth’s coarse stem characteristics, which prolong drying time for up to five days when field cured.

Gamagrass is also well adapted to the Upper South, being a perennial, native, multipurpose grass. It has been successfully grazed—both continuously and rotationally—and conserved as hay and is a potential biomass source. Like switchgrass, gamagrass has thick stems and wide leaves. But unlike switchgrass, it cures fairly rapidly in the field when preserved as hay. During rainy periods, however, it would be desirable to reduce the risk of hay loss from rain by preserving gamagrass as either baleage or silage.

This bulletin consists of two sections. In Section I we present our experiments with switchgrass, and in Section II we present our experiments with gamagrass. Both forages were evaluated as silages, whether ensiled as baleage or direct-cut or wilted. These silages were generally compared with hay from the same source that had been either field cured or forced-air dried. Differences were detected in fermentation characteristics, nutritive value of the hays and silages, and their subsequent quality. Our main focus in this bulletin, however, is to provide a record of the data obtained from several different experiments designed to evaluate characteristics of these perennial, warm-season grasses that might contribute to improved animal daily performance during stressful periods. Only the main points from each experiment have been highlighted in each Results and Discussion section and in each Summary and Conclusions section. The general procedures used in conducting this research are presented in the Appendix. Throughout the bulletin, “nutritive value” refers to laboratory estimates of in vitro dry matter disappearance and the chemical composition of the forage—such as crude protein and neutral detergent fiber, and “quality” refers to animal responses to the forage—such as dry matter intake, dry matter digestibility, and masticate characteristics.

Section I. Switchgrass

Experiment 1. Initial Growth Switchgrass Cut in the Vegetative Stage: Ensiling Characteristics, Nutritive Value, and Quality

Experiment 2. Switchgrass Cut in the Late-Boot Stage: Ensiling Characteristics, Nutritive Value, and Quality

Experiment 3. Initial Growth Switchgrass Cut in the Headed Stage: Ensiling Characteristics, Nutritive Value, and Quality

Experiment 4. Regrowth Switchgrass Cut in the Heading Stage: Ensiling Characteristics, Nutritive Value, and Quality

Experiment 1. Initial Growth Switchgrass Cut in the Vegetative Stage: Ensiling Characteristics, Nutritive Value, and Quality

Our objective in this experiment was to assess and compare the fermentation characteristics, nutritive value, and quality of initial-growth switchgrass when cut in the late-vegetative stage and preserved as forced-air-dried hay, direct-cut silage, or wilted silage.

Material and Methods

A well-established stand of Kanlow switchgrass provided the experimental forage. The field was burned in mid-February to remove all fall carryover growth. In mid-March nitrogen was applied at the rate of 80 pounds per acre. The initial growth was cut June 14 in the late-vegetative stage (mean height = 48 inches), and the following three treatments were preserved for evaluation:

Hay: flail chopped, barn dried at 145°F, baled
Silage, direct-cut: cut, chopped, ensiled directly
Silage, wilted: cut, wilted, chopped, ensiled

Forage for the hay treatment was flail chopped to a 5-inch stubble, blown into a self-unloading wagon, and dried overnight in a bulk dryer (inlet set at 145°F). Forage for the two silage treatments was cut with a mower-conditioner set to a 5-inch stubble. Forage for the direct-cut treatment was immediately chopped with a field chopper, blown into a self-unloading wagon, and transported for ensiling at the NC State University Forage-Animal Metabolism Unit in Raleigh, NC. Forage for the wilted treatment was left in the field longer after cutting based on dry matter estimates and then handled as noted for the direct-cut treatment. For both silage treatments, the forage was ensiled in upright experimental silos lined with plastic. The forage was treaded at filling to exclude oxygen and the plastic liner tied at the top and left until feeding (late fall) (Appendix GP-2). The forage (hay or silage) was processed at feeding according to normal procedures (Appendix GP-1).

An intake and digestibility experiment was conducted using twelve steers (mean weight = 587 ± 21.9 pounds) in a randomized complete block design with four steers (replicates) per treatment. The steers were grouped in threes by weight and randomly assigned to a treatment within each group. The intake and digestibility experiment was conducted according to normal procedures (Appendix GP-3). All as-fed, weighback, and fecal samples were analyzed according to normal procedures (Appendix GP-6), and the data were statistically analyzed according to the experimental design (Appendix GP-7).

Results and Discussion

Although vegetative, the forage evaluated in this experiment averaged 59.4% stem (sheath) and 40.6% leaf. The direct-cut silage averaged 28% dry matter, and the wilted had dried to 46% dry matter at ensiling (Table 1.1). Both silages fermented reasonably well with the pH averaging below 5.0 (Table 1.1). The direct-cut silage, however, had the lowest pH, consistent with greater acetic, lactic, and butyric acid concentrations. The propionic acid concentration was similar in both direct-cut and wilted silages. The direct-cut silage also had greater concentrations of ethanol with the presence of some butanol, whereas the wilted had only traces of butanol.

Steers consumed the switchgrass hay and silages similarly, although intakes of the silages were generally greater than intakes of hay and approached significance (P = 0.08) (Table 1.2). The digestibility of the dry matter and constituent fiber fractions were generally not altered by preservation method. A noted exception was hemicellulose, which was more digestible for the hay. The favorable intakes of the silages are reflected in the digestible intakes all being significantly greater for silages than hay and greater for wilted than for direct-cut silage (Table 1.2).

The in vitro dry matter disappearance of the as-fed forages was greater for silages versus hay (Table 1.3), and the neutral detergent fiber (NDF) was less for silages versus hay and consistent with dry matter intake (Table 1.2). The other nutritive differences were generally small and probably of little biological importance. Some selective consumption occurred as noted by difference values (weighback concentration minus as-fed concentration), with greater selectivity occurring for hay than for the silages and some indication of selectivity for wilted silage over direct-cut, but only the difference value for NDF was significant (Table 1.3).

Summary and Conclusions

Initial-growth switchgrass can be ensiled directly or when wilted in the late-vegetative stage.
The pH of the silage—whether cut and ensiled directly or wilted and ensiled—was below 5.0, and both silages appeared stable.
Steers consumed both silages and the hay similarly, averaging 1.65 pounds of dry matter per 100 pounds of body weight with some advantage in favor of silage (1.72 lb) compared with hay (1.53 lb).
Steers digested the silages and hay similarly (60.7%), but digestible dry matter intake was greater for silages and reflected the greater dry matter intake.

Table 1.1. Dry matter (DM) concentration and fermentation characteristics of late-vegetative switchgrass preserved as silage (DM basis).
Treatment	DM	pH	Alcohol			Fatty Acids
	DM		Ethanol	Methanol	Butanol	Acetic	Propionic	Lactic	Butyric
	%		————————————————%———————————————
Direct Cut¹	27.9	4.3	0.52	0.02	0.08	1.05	0.05	0.57	0.31
Wilted²	46.1	4.8	0.19	0.02	t³	0.61	0.03	0.24	0.05
SD⁴	10.5	0.3	0.22	0.01	0.08	0.27	0.02	0.18	0.27

¹ Each value is the mean of four samples.

² Each value is the mean of two samples.

³ t = trace.

⁴ SD = standard deviation.

Table 1.2. Dry matter (DM) intake (DMI), digestibility, and digestible intakes of DM and associated nutritive values¹ of late-vegetative switchgrass preserved as hay and silage (DM basis).
Treatment	DMI	Digestibility					Digestible Intake
	DMI	DM	NDF	ADF	HEMI	CELL	DM	NDF	ADF	HEMI	CELL
	lb/100 lb²	———————% ———————					———————lb/100 lb ——————
Hay (H)	1.53³	61.7	62.7	57.4	68.2	67.2	0.94	0.70	0.32	0.38	0.32
Silage (S):
Direct Cut (DC)	1.68	59.5	59.3	57.5	61.5	66.9	1.00	0.71	0.38	0.33	0.37
Wilted (WT)	1.75	60.9	61.7	58.4	65.8	67.2	1.12	0.82	0.42	0.40	0.41
Significance (P):
Treatment	0.16	0.34	0.18	0.93	0.01	0.97	0.01	0.02	<0.01	0.01	<0.01
H vs. S	0.08	0.30	0.21	0.79	0.02	0.92	0.01	0.03	<0.01	0.24	<0.01
DC vs. WT	0.53	0.47	0.30	0.76	0.06	0.90	0.02	0.01	0.03	0.01	0.03

¹ NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Body weight basis.

³ Each value is the mean of four steers.

Table 1.3. In vitro dry matter disappearance (IVDMD) and nutritive value¹ of as-fed (AF) late-vegetative switchgrass preserved as hay and silage (dry matter basis).
Treatment	IVDMD		CP		NDF		Fiber Fractions
	AF	DV²	AF	DV	AF	DV	ADF	HEMI	Cell	Lignin
	—————————————————% —————————————————
Hay (H)	52.9³	-6.2	6.9	-3.7	74.0	6.1	37.9	36.1	32.2	4.9
Silage (S):
Direct Cut (DC)	57.5	-3.2	5.8	0.7	71.4	1.0	39.2	32.2	33.4	5.0
Wilted (WT)	54.4	-2.7	5.8	0.2	73.6	2.9	40.5	33.2	34.2	5.3
Significance (P):
Treatment	<0.01	0.07	0.02	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	0.08
H vs. S	<0.01	0.03	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	0.13
DC vs. WT	<0.01	0.68	0.99	0.15	<0.01	<0.01	0.02	<0.01	<0.01	0.07
MSD⁴	1.8	3.3	0.8	0.8	0.8	1.0	1.0	0.2	0.8	0.4

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² DV = difference value (weighback concentration minus AF concentration).

³ Each value is the mean of four samples.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Experiment 2. Switchgrass Cut in the Late-Boot Stage: Ensiling Characteristics, Nutritive Value, and Quality

Our objective in this experiment was to assess and compare the fermentation characteristics, nutritive value, and quality of initial-growth switchgrass cut in the late-boot stage and preserved as silage (direct-cut or wilted) or hay (field-cured or forced-air-dried).

Material and Methods

A well-established stand of Alamo switchgrass provided the experimental forages. The field was burned in late February to remove all fall carry-over growth. In mid-March nitrogen was applied at 70 pounds per acre, and the initial growth was allowed to mature to the late-boot stage with heads emerging. Four treatments were cut between June 27 and June 28 for evaluation:

Silage: cut, immediately ensiled
Silage: cut, wilted, ensiled
Hay: cut, field cured, baled
Hay: cut, forced-air dried (165°F), baled

Forages to be ensiled were cut with a mower conditioner to a 5-inch stubble. The immediately ensiled forage was chopped with a field chopper, blown into a self-unloading wagon, and transported for ensiling at the NC State University, Forage-Animal Metabolism Unit, Raleigh, NC. Forage for the wilted treatment was left in the field longer after cutting based on dry matter estimates and handled as noted above for the immediately ensiled treatment. Forages for ensiling were unloaded into an upright fiberglass silo lined with plastic. The forage was packed by treading as the silo was filled, and the top of the plastic liner tied-off when filled (Appendix GP-2). Forage preserved as field-cured hay was cut with a mower-conditioner set to a 5-inch stubble, tedded daily to aid drying, and square baled with a conventional square baler. Forage preserved as forced-air-dried hay was cut with a flail chopper to a 5-inch stubble, blown into a self-unloading wagon, unloaded into a bulk-drying barn, and dried at 165°F. After drying (to about 90% dry matter), the forage was square baled directly from the dryer. All square bales were transported to the experimental hay barn at the NC State University Forage-Animal Metabolism Unit, Raleigh, NC, and stored by treatment on wooden pallets until fed. The hays were processed prior to feeding according to normal procedures (Appendix GP-1).

The two silage treatments were opened at initiation of the study and all mold removed from the top of the silo. Sufficient silage was removed daily to keep the silo surface fresh. Silage that was retained in the feed cart between feedings was covered with plastic to exclude oxygen.

Two experiments were conducted. Experiment 2A was conducted with steers and evaluated dry matter intake and digestibility. Experiment 2B was conducted with esophageally cannulated steers and evaluated characteristics of the diet through masticate collection. A randomized complete block design with five replicates was used in Experiment 2A. Twenty steers (mean weight = 506 pounds) were grouped by fours based on similar weight and assigned at random to a hay or silage treatment within each of the five replicates. The intake and digestibility experiment was conducted according to normal procedures (Appendix GP-3).

In Experiment 2B, six fistulated steers were used in a randomized complete block design. Steers were fed two different treatments on day 1 and day 2. Masticate collection, processing, and particle size determination were conducted according to normal procedures (Appendices GP-4 and GP-5). The collected samples were split: One part was used for nutritive value estimates and the other part sieved to determine median particle size and the particle-size classes of large, medium, and small (Appendix GP-5).

All as-fed, weighback, whole masticate, and fecal samples, as well as dry matter for each particle-size class of masticate, were analyzed according to normal procedures (Appendix GP-6). All variables were statistically analyzed according to the experimental design (Appendix GP-7).

Results and Discussion

Experiment 2A

Steers consumed all four forages similarly—whether hay or silage—averaging 1.35 pounds per 100 pounds of body weight (Table 2.1). Further, all four forages were digested similarly, with digestibility of the dry matter averaging 52.3%. Digestible dry matter intake, however, differed: That of the barn-dried hay (0.79 lb/100 lb body weight) was greater than that of the other treatments (0.68 lb/100 lb body weight). The digestibility of hemicellulose was also greater in the barn-dried hay and reflected in the digestible hemicellulose intake compared among the four treatments.

Examination of the fermentation characteristics of the ensiled forages fed during the intake phase indicated that direct-cut and wilted silages differed in composition (Table 2.2). The dry matter (goal was 35 to 36%) of the direct-cut silage was less than that of the wilted, and the pH was lower. Associated with the lesser pH of the direct-cut silage were greater concentrations of alcohol and acetic, propionic, and butyric acids, with lactic acid least. Silage fed in the digestibility phase produced similar trends. Neither of the silages fermented to the extent needed to give a stable product, which would be expected to have a pH in the range of 4.0 to 4.5. This is attributed, in part, to a lack of soluble carbohydrates for conversion by microflora to volatile fatty acids.

The nutritive constituents of the barn-dried hay are generally more favorable than those of the other forage treatments, being greater in in vitro dry matter disappearance and associated with lesser neutral detergent fiber, acid detergent fiber, cellulose, and lignin (Table 2.3). These nutritive differences are attributed mainly to the more rapid termination of respiration in barn-dried hay. The difference values (weighback concentration minus as-fed concentration) indicate that some selective consumption may have occurred between field-cured hay and the silages, and between silages, but the differences were present only for crude protein and greater for hay compared with silage. This indicates that selection of leaf tissue greater in crude protein may have been easier for steers fed hay.

Experiment 2B

Masticate dry matter was similar between silages and between hays but was greater for hays than silages (Table 2.4). Within silages, the whole masticate of the direct-cut silage had smaller median particle size and greater in vitro true dry matter disappearance than did the wilted. Whole masticate of field-cured hay had greater median particle size compared with that of the silages and had greater in vitro true dry matter disappearance, crude protein, and neutral detergent fiber. Masticates from the barn-dried hay and the field-cured hay were similar in median particle size and in vitro dry matter disappearance. The hays had greater proportions of the dry matter as large particles and lesser proportions as small particles than the silages. All forages had a similar proportion of medium-sized particles. Further, differences in nutritive values among treatments occurred within the particle-size classes. Within the silages, crude protein was greater for wilted silage than for direct-cut in both the large and medium particle-size classes with no difference for the small particle-size class (Table 2.4). Masticate from field-cured hay had greater in vitro true dry matter disappearance and crude protein and lesser neutral detergent fiber in all three particle-size classes compared with the silages. This is attributed mainly to the fermentation process, in which portions of the silage dry matter are converted to volatile fatty acids. Masticate characteristics of the barn-dried hay closely resembled those of the field-cured hay compared with the ensiled treatments. This is more readily seen by the distribution of the masticate particle sizes (Figure 2.1).

The chemical composition of the feces indicates that some difference in how the forages were processed may have occurred. Although the two silages appear to have been processed similarly, feces from steers fed the field-cured hay had greater concentrations of hemicellulose and lesser concentrations of lignin than feces from steers fed the silages (Table 2.5). This difference was more extensive for the barn-dried hay. Feces from steers fed the barn-dried treatment had greater concentrations of crude protein and acid detergent fiber than feces from steers fed the other treatments.

Summary and Conclusions

Switchgrass cut in the late-boot stage was preserved as silage, but the fermentation process was limited—with pH being reduced to only about 5.2—and attributed to a lack of available soluble carbohydrates for the fermentation process.
Steers consumed ensiled switchgrass, whether direct cut or wilted prior to ensiling, similarly to field-cured or barn-cured hays.
Switchgrass preserved when cut in the late-boot stage has inherent constraints in crude protein concentrations and dry matter digestibility for desirable animal performance without proper supplementation.

Table 2.1. Dry matter (DM) intake (DMI), digestibility, and digestible intakes of DM and associated nutritive value¹of late-boot switchgrass preserved as silage and hay, Experiment 2A (DM basis)
Treatment	DMI	Digestibility					Digestible Intake
	DMI	DM	NDF	ADF	HEMI	CELL	DM	NDF	ADF	HEMI	CELL
	lb/100 lb²	———————————%————————					——————lb/100 lb—————————
Silage (S):
Direct Cut (DC)	1.24³	50.3	54.1	56.3	51.0	63.1	0.62	0.52	0.31	0.21	0.30
Wilted (WT)	1.36	53.3	55.9	55.7	56.1	62.7	0.72	0.58	0.33	0.24	0.32
Hay:
Field cured (FC)	1.36	51.1	53.1	53.1	53.0	59.8	0.70	0.55	0.30	0.25	0.29
Barn dried (BD)	1.45	54.6	55.9	52.9	58.9	60.0	0.79	0.61	0.29	0.31	0.29
Significance (P):
Treatment	0.27	0.52	0.73	0.58	0.11	0.51	0.08	0.27	0.51	<0.01	0.49
DC vs. WT	0.26	0.35	0.56	0.35	0.12	0.90	0.11	0.19	0.49	0.05	0.38
FC vs. (DC+WT)	0.52	0.82	0.46	0.82	0.84	0.21	0.60	0.98	0.37	0.28	0.29
BD vs. Others	0.13	0.26	0.55	0.26	0.05	0.41	0.04	0.14	0.33	<0.01	0.49
MSD⁴	0.27	8.6	8.4	8.4	7.6	7.5	0.14	0.12	0.07	0.05	0.06

¹ NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Body weight basis.

³ Each value is the mean of five steers.

⁴MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 2.2. Dry matter (DM) concentration and fermentation characteristics of late-boot switchgrass preserved as silage, Experiment 2A (DM basis).
Treatment	DM	pH	Alcohol	Fatty Acids
	DM		Ethanol	Acetic	Propionic	Lactic	Butyric
	%		—————————— %——————————
Intake Phase:
Direct Cut (DC)	29.7¹	5.2	1.16	1.44	0.08	0.10	0.48
Wilted (WT)	31.7	5.5	0.48	0.91	0.02	0.19	0.19
Significance (P)	0.01	0.02	0.06	<0.01	<0.01	<0.01	<0.01
Digestion Phase:
Direct Cut (DC)	31.2	5.3	0.93	1.21	0.06	0.12	0.48
Wilted (WT)	34.9	5.9	0.20	0.41	—	0.21	0.07
Significance (P)	0.03	0.08	<0.01	<0.01	<0.01	0.02	<0.01

¹ Each value is the mean of five samples.

Table 2.3. In vitro dry matter disappearance (IVDMD) and nutritive value¹ of as-fed (AF) late-boot switchgrass preserved as silage and hay, Experiment 2A (dry matter basis).
Treatment	IVDMD		CP		NDF		Fiber Fractions
	AF	DV²	AF	DV	AF	DV	ADF	HEMI	CELL	Lignin
	——————————————————%———————————————————
Silage (S):
Direct Cut (DC)	55.9³	-7.5	5.0	-1.2	78.1	3.4	45.3	32.7	39.5	5.5
Wilted (WT)	56.7	-11.7	5.4	-1.8	77.7	6.1	44.5	33.2	38.9	5.4
Hay:
Field cured (FC)	55.5	-9.4	5.1	-2.8	76.8	5.2	42.5	34.3	36.9	5.5
Barn dried (BD)	60.6	-7.9	5.4	-2.3	75.8	5.0	39.3	36.6	34.7	4.5
Significance (P):
Treatment	<0.01	0.25	0.33	0.01	<0.01	0.12	<0.01	<0.01	<0.01	<0.01
DC vs. WT	0.44	0.07	0.15	0.14	0.31	0.02	0.04	0.17	0.07	0.37
FC vs. (DC+WT)	0.31	0.94	0.74	<0.01	0.01	0.63	<0.01	<0.01	<0.01	0.69
BD vs. Others	<0.01	0.37	0.27	0.26	<0.01	0.91	<0.01	<0.01	<0.01	<0.01
MSD⁴	0.6	5.5	0.7	0.9	0.8	2.5	0.7	0.6	0.6	0.3

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

²DV = difference value (weighback concentration minus AF concentration).

³ Each value is the mean of five samples.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 2.4. Whole-masticate dry matter (DM), median particles size (MPS), and particle-size classes¹ and associated nutritive value²of late-boot switchgrass preserved as silage and hay, Experiment 2B (DM basis).
Treatment	Whole Masticate					Particle-size Classes
	Whole Masticate					Large				Medium				Small
	DM	MPS	IVTD	CP	NDF	Prop³	IVTD	CP	NDF	Prop	IVTD	CP	NDF	Prop	IVTD	CP	NDF
	%	mm	———————————————————————— %———————————————————————
Silage (S):
Direct Cut (DC)	12.8⁴	1.1	63.0	4.9	71.6	30.6	55.8	3.6	78.4	41.2	60.0	4.4	74.3	28.2	72.0	6.6	65.6
Wilted (WT)	13.2	1.3	61.7	5.2	71.6	37.1	52.4	4.5	79.4	41.9	61.1	5.0	73.2	21.0	71.5	7.0	63.9
Hay:
Field cured (FC)	16.6	1.9	68.6	6.0	73.2	53.0	62.2	4.4	77.4	38.6	70.6	6.4	71.5	8.4	78.9	8.2	62.4
Barn dried (BD)	17.5	1.7	69.8	5.7	71.0	47.8	63.1	4.3	76.5	41.6	72.2	6.1	69.3	10.6	78.3	7.3	61.9
Significance (P):
Treatments	<0.01	<0.01	<0.01	0.01	0.09	<0.01	<0.01	<0.01	0.02	0.40	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
DC vs. WT	0.44	0.05	0.03	0.25	0.97	0.04	0.13	0.03	0.24	0.73	0.13	0.01	0.11	<0.01	0.52	0.17	0.06
FC vs. (DC+WT)	<0.01	<0.01	<0.01	<0.01	0.04	<0.01	<0.01	<0.01	0.05	0.12	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	0.01
BD vs. Others	<0.01	<0.01	<0.01	0.20	0.10	0.01	<0.01	0.57	0.01	0.56	<0.01	<0.01	<0.01	<0.01	<0.01	0.95	0.01
MSD⁵	1.1	0.2	1.1	0.6	1.9	5.7	1.7	0.5	1.9	5.6	1.3	0.4	1.3	3.1	1.4	0.5	1.7

¹ Large = > 1.7mm; medium = ≤1.7mm and >0.5mm; small < 0.5 mm.

² IVTD = in vitro true dry matter disappearance; CP = crude protein; NDF = neutral detergent fiber.

³Prop = proportion of dry matter.

⁴ Each value is the mean of six steers.

⁵ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 2.5. Chemical composition¹of feces from steers fed late-boot switchgrass preserved as silage and hay, Experiment 2B (dry matter basis).
Treatment	CP	NDF	ADF	HEMI	CELL	Lignin
Treatment	—————————— % ——————————
Silage (S):
Direct Cut (DC)	7.2²	72.9	40.3	32.6	29.6	10.1
Wilted (WT)	6.7	74.1	41.5	32.5	30.6	10.2
Hay:
Field cured (FC)	7.0	73.2	40.0	33.2	29.7	9.7
Barn dried (BD)	7.7	72.4	39.1	33.3	29.4	8.7
Significance (P):
Treatment	0.05	0.32	0.02	0.01	0.38	<0.01
DC vs. WT	0.22	0.20	0.09	0.76	0.18	0.35
FC vs. (DC+WT)	0.73	0.76	0.15	0.01	0.55	0.02
BD vs. Others	0.01	0.19	0.01	0.01	0.34	<0.01
MSD³	0.8	2.3	1.5	0.5	1.8	0.4

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

²Each value is the mean of five steers.

³ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Line graph cumulative percent oversize vs. sieve size (mm)

Figure 2.1. Particle size distribution of masticate dry matter of late-boot switchgrass preserved as hay or silage (n=6).

Experiment 3. Initial Growth Switchgrass Cut in the Headed Stage: Ensiling Characteristics, Nutritive Value, and Quality

Our objective in this experiment was to assess and compare the fermentation characteristics, nutritive value, and quality of switchgrass in the headed stage when preserved as silage (direct-cut or wilted) and forced-air-dried hay.

Materials and Methods

A well-established stand of Kanlow switchgrass provided the experimental forage. The field was burned in mid-February to remove all fall carryover growth. In mid-March nitrogen was applied at 80 pounds per acre. The initial growth was cut August 21 when fully headed (mean height = 76 inches), and the following three treatments were preserved for evaluation:

Hay: flail chopped, bulk-barn dried at 145°F, baled as hay
Silage, direct-cut: cut, chopped, ensiled directly
Silage, wilted: cut, wilted, chopped, ensiled

Forage for the hay treatment was flail chopped to a 5-inch stubble, blown into a self-unloading wagon, and dried overnight in a bulk-barn dryer. Forages for the silage treatments were cut with a mower conditioner, also set to leave a 5-inch stubble. Forage for the direct-cut treatment was immediately chopped with a field chopper, blown into a self-unloading wagon, and transported for ensiling to the NC State University Forage-Animal Metabolism Unit, Raleigh, NC. Forage for the wilted treatment was left in the field longer after cutting, based on dry matter estimates, and chopped with a field chopper, blown into a self-unloading wagon, and transported as noted for the direct-cut treatment. Both treatments were ensiled similarly, with the forage ensiled in upright experimental silos lined with plastic. The forage was treaded at filling to exclude oxygen and the plastic liner tied at the top and left until feeding (late fall) (Appendix GP-2). The forage (hay or silage) was processed at feeding according to normal procedures (Appendix GP-1).

Two experiments were conducted consisting of an intake and digestibility experiment (Experiment 3A) and a separate mastication experiment (Experiment 3B). In the intake and digestibility experiment, 12 steers (mean weight = 498 ± 31.2 pounds) were used in a randomized complete block design. The steers were grouped by threes into four blocks by weight and randomly assigned to treatments within blocks. The intake and digestibility experiment was conducted using normal procedures (Appendix GP-3).

The mastication experiment was conducted with three esophageally cannulated steers in a Latin square design with periods consisting of sequential days. The steers were standardized on their next treatment the day prior to collection. All collections were obtained at the morning feeding, and sample collection, processing, and particle size determination handled according to normal procedures (Appendices GP-4 and GP-5).

All as-fed, weighback, masticate, and fecal samples were analyzed according to normal procedures (Appendix GP-6) and the data statistically analyzed according to the experimental design (Appendix GP-7).

Results and Discussion

Silages used in both Experiment 3A and 3B fermented reasonably well with the pH below 5.0 (Table 3.1). It is noted that the direct-cut silage fermented better (pH 4.2) than the wilted, having greater concentrations in acetic, lactic, and butyric acids. Both silages had similar patterns in alcohol concentrations.

Experiment 3A

Dry matter intake was similar among all treatments, averaging 1.07 pounds of dry matter per 100 pounds of body weight, and reflects the advanced maturity of switchgrass (Table 3.2). This is further indicated by the similar and limited dry matter digestibility, averaging 42.9%. In general, method of preservation had no influence on the nutritive value or quality of this well-headed switchgrass.

The nutritive value of the as-fed forage reflects the limited dry matter intake and digestibility, with crude protein less than 3.4% and neutral detergent fiber more than 81% (Table 3.3). In this experiment, the as-fed samples from the four animal replicates were pooled prior to analysis, so no statistical comparisons are possible. However, difference values (weighback concentration minus as-fed concentration) were estimated and indicate that no obvious selective consumption occurred.

Experiment 3B

Characterization of the whole masticates essentially revealed no differences in median particle size or nutritive value from preservation method (Table 3.4). The masticate dry matter averaged 36.2% large particles, 48.0% medium, and 15.8% small particles, with little difference among preservation methods in proportion of particle-size classes or in nutritive value within classes (Table 3.4).

During the mastication process, steers incorporated appreciable saliva, decreasing the dry matter of the as-fed forage that was 28% and greater to 17% and less (Table 3.5). Dry matter concentrations in boluses from hay and silage and between silages were similar, but differences approached significance (P = 0.08). The number of chews per gram of dry matter and neutral detergent fiber were similar between hay and silages, but the differences approached significance (P = 0.07). However, the direct-cut silage had greater chews per gram of both dry matter and gram of neutral detergent fiber compared with the wilted silage.

The undigested dry matter excreted as feces also reflected little difference in either median particle size or in neutral detergent fiber among the samples, although the neutral detergent fiber concentration was greater for hay compared with that of the silages, which were similar (Table 3.4)

Summary and Conclusions

1. Switchgrass that is well headed can be preserved as either direct-cut or wilted silage.

2. Dry matter intake was not altered by method of preservation and averaged 1.07 pounds per 100 pounds of body weight with an average dry matter digestibility of 42.9%.

3. Hay or silage of headed Kanlow switchgrass was of poor nutritive value and of very limited quality.

Table 3.1. Dry matter (DM) concentration and fermentation characteristics of headed switchgrass preserved as silage, Experiment 3A and 3B (DM basis).
Treatment	DM	pH	Alcohol			Fatty Acids
	DM		Ethanol	Methanol	Butanol	Acetic	Propionic	Lactic	Butyric
	%		———————————————%———————————————
Direct Cut¹	28.1	4.2	0.18	0.01	t²	0.84	0.08	3.4	0.66
Wilted³	60.1	4.9	0.01	0.01	—	0.16	0.06	1.1	0.05
SD⁴	17.40	0.50	0.145	0.004	—	0.390	0.045	1.32	0.396

¹ Each value is the mean of four samples.

² t = trace.

³ Each value is the mean of two samples.

⁴ SD = standard deviation.

Table 3.2. Dry matter (DM) intake (DMI), digestibility, and digestible intakes of DM and associated nutritive value¹ of headed switchgrass preserved as hay and silage, Experiment 3A (DM basis).
Treatment	DMI	Digestibility					Digestible Intake
	DMI	DM	NDF	ADF	HEMI	CELL	DM	NDF	ADF	HEMI	CELL
	lb/100 lb²	———————— % ————————					——————lb/100 lb ——————
Hay (H)	1.04³	43.5	44.6	42.1	48.5	47.2	0.45	0.38	0.21	0.16	0.19
Silage (S):
Direct Cut (DC)	1.11	43.2	46.2	42.7	51.7	48.7	0.49	0.42	0.23	0.18	0.21
Wilted (WT)	1.07	42.1	44.9	42.2	49.1	48.6	0.45	0.39	0.22	0.17	0.21
Significance (P):
Treatment	0.16	0.91	0.86	0.98	0.58	0.82	0.63	0.47	0.45	0.06	0.23
H vs. S	0.10	0.78	0.73	0.89	0.52	0.55	0.66	0.32	0.33	0.33	0.12
DC vs. WT	0.33	0.75	0.69	0.87	0.43	0.95	0.41	0.48	0.43	0.56	0.52
MSD⁴	0.09	8.6	8.4	8.2	8.6	7.4	0.11	0.09	0.05	0.04	0.03

¹ NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Body weight basis.

³Each value is the mean of four steers.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 3.3. In vitro dry matter disappearance (IVDMD) and nutritive value¹ of as-fed (AF) headed switchgrass preserved as hay and silage, Experiment 3A (dry matter basis).
Treatment	IVDMD		CP		NDF		FiberFractions
	AF	DV²	AF	DV	AF	DV	ADF	HEMI	CELL	Lignin
	—————————————————%—————————————————
Hay (H)	28.1³	-4.6⁴	2.6³	-1.14	81.5³	3.2⁴	49.3³	32.2³	39.0³	9.5³
Silage (S):
Direct Cut (DC)	35.0	-6.3	3.2	-0.9	81.1	2.5	49.6	31.5	39.4	8.8
Wilted (WT)	32.4	-4.2	2.4	-0.5	82.4	1.8	49.4	32.9	39.6	8.5
Significance (P):
Treatment	—	0.56	—	0.15	—	0.16	—	—	—	—
H vs. S		0.71		0.13		0.09
DC vs. WT		0.33		0.19		0.34
MSD⁵		5.2		0.7		1.7

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² DV = difference value (weighback concentration minus AF concentration).

³ Each value represents the composite of four samples and not subjected to statistical analysis.

⁴ Each value is the mean of four samples.

⁵ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 3.4. Whole-masticate and feces median particle size (MPS), masticate particle-size classes, and associated nutritive value¹ and feces fiber concentration from steers fed headed switchgrass preserved as hay and silage, Experiment 3B (dry matter basis).
Treatment	Masticate²												Whole⁴ Feces
	Whole Masticate			Particle-size Classes³									Whole⁴ Feces
	Whole Masticate			Large			Medium			Small			%
	MPS	IVTD	NDF	Prop⁵	IVTD	NDF	Prop	IVTD	NDF	Prop	IVTD	NDF	MPS	NDF
	mm	————————————————————% ———————————————————											mm	%
Hay (H)	1.3	38.5	78.5	37.0	35.7	82.5	47.9	38.2	78.4	15.1	46.7	68.9	0.2	79.1
Silage (S):
Direct Cut (DC)	1.2	36.6	80.5	33.6	31.0	83.4	49.3	37.7	80.7	17.1	44.7	74.4	0.2	77.2
Wilted (WT)	1.3	36.5	80.6	38.1	33.4	83.5	46.7	36.2	80.8	15.2	46.8	73.2	0.2	77.5
Significance (P):
Treatment	0.94	0.66	0.56	0.94	0.39	0.67	0.92	0.10	0.26	0.79	0.96	0.16	0.16	0.03
H vs. S	0.92	0.42	0.34	0.93	0.40	0.27	0.99	0.10	0.14	0.77	0.89	0.08	0.12	0.01
DC vs. WT	0.78	0.96	0.96	0.77	0.45	0.91	0.71	0.09	0.95	0.59	0.83	0.56	0.21	0.59
MSD⁶	1.0	7.0	6.1	40.2	8.7	3.7	18.7	1.8	4.1	21.6	10.0	6.3	0.04	1.4

¹ IVTD = in vitro true dry matter disappearance; NDF = neutral detergent fiber.

² Each value is the mean of three steers.

³ Large = > 1.7mm; medium = ≤1.7mm and >0.5mm; small < 0.5 mm.

⁴ Each value is the mean of four steers.

⁵ Prop = proportion of dry matter.

⁶ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 3.5. Bolus characteristics and chewing behavior of steers fed headed switchgrass preserved as hay and silage, Experiment 3B (dry matter basis).
Treatment	Forage DM¹	Bolus		Chewing Activity
	Forage DM¹	DM	Weight	Number	Sec²	Per g DM	Per g NDF³
	———% ——		grams	——per bolus —		No.	No.
Hay (H)	91.1	17.0⁴	6.8	22.7	22.8	3.1	4.0
Silage (S):
Direct Cut (DC)	28.1	11.2	2.5	20.3	19.4	8.2	10.2
Wilted (WT)	60.1	15.6	5.4	20.9	19.3	4.2	5.2
Significance (P):
Treatment	—	0.08	0.17	0.77	0.64	0.06	0.07
H vs. S	—	0.08	0.14	0.54	0.40	0.07	0.07
DC vs. WT	—	0.08	0.18	0.88	0.99	0.05	0.05

¹ Dry matter; each value is the composite of three samples.

² Sec = seconds.

³ Neutral detergent fiber.

⁴ Each value is the mean of three steers.

Experiment 4. Regrowth Switchgrass Cut in the Heading Stage: Ensiling Characteristics, Nutritive Value, and Quality

Our objective in this experiment was to assess and compare the fermentation characteristics, nutritive value, and quality of the finer, headed-out, regrowth switchgrass when preserved as silage (direct cut or wilted) and forced-air-dried hay.

Materials and Methods

A well-established stand of Kanlow switchgrass provided the experimental forage. The initial growth was removed June 18 and the field topdressed with 80 pounds of nitrogen per acre in preparation for the subsequent regrowth. The regrowth was 95% headed (40 – 48 inches in height) when cut on September 24. The following three treatments were prepared for evaluation:

Silage, direct-cut: cut, directly ensiled in upright silo
Silage, wilted: cut, wilted overnight, ensiled in upright silo
Hay: cut, forced-air dried, baled

All treatments were cut with a mower-conditioner set to a 5-inch stubble. Both the direct-cut and wilted silages were chopped and blown into a self-unload- ing wagon and the forage placed in upright fiberglass silos. The silos were lined with plastic, the forage treaded when placed into the silos, and the top of the plastic tied-off when the silo was full (Appendix GP- 2). The forage for hay was dried (inlet set at 160°F) overnight, square baled from the dryer, and stored on wooden pallets in the experimental hay barn at the NC State University Forage-Animal Metabolism Unit, Raleigh, NC (Appendix GP-1).

Two experiments were conducted. One experiment (Experiment 4A) evaluated dry matter intake and digestibility, and the other (Experiment 4B) evaluated masticate characteristics. Intake and digestibility were evaluated in a randomized complete block design with four steers (replicates) per treatment. The steers (mean weight = 508 ± 43 pounds) were grouped in fours by weight and a steer within each group (replicate) randomly assigned to a treatment. The steers were fed an average of 13.1% excess, and the experiment was conducted according to normal procedures (Appendix GP-3).

The mastication experiment (Experiment 4B) was conducted with three esophageally fistulated steers in a Latin square design. Steers were assigned at random to a treatment in period one. Masticate samples were obtained in the a.m. and the p.m. for two consecutive days, and sample collection, processing, and particle size determination were conducted according to normal procedures (Appendices GP-4 and GP-5).

All as-fed hay, weighback, and masticate samples were analyzed for nutritive value, and fecal samples were analyzed for chemical composition according to normal procedures (Appendix GP-6). The data were statistically analyzed according to the experimental design (Appendix GP-7).

Results and Discussion

The switchgrass cut at 95% heading was predominantly stems, averaging 65% stems with 25% leaf and 10% head (dry matter basis). Examination of the ensiling characteristics, however, indicates that the headed switchgrass fermented surprising well. The direct-cut treatment had least dry matter compared to the wilted, as expected, and had lesser pH, greater concentrations of acetic and lactic acid, and lesser butyric acid (Table 4.1). The extent of fermentation, as noted by pH, is attributed, in part, to the stem fineness of switchgrass regrowth, allowing better packing and exclusion of more oxygen.

Experiment 4A

Steers consumed more of the hay compared with the silages, and greater wilted silage was consumed than direct-cut silage (Table 4.2). Digestibilities of the various fractions were similar between hay and silages, whereas wilted silage was generally more digestible than the direct-cut silage. The greater dry matter intake of hay compared with the silages, and of wilted silage compared with direct-cut silage, is reflected similarly in the digestible intakes.

The nutritive value of the hay was generally superior to the silages (Table 4.3) and reflected in steer dry matter intake (Table 4.2). Also the nutritive value of the wilted silage was similar or greater than that of the direct-cut silage.

Experiment 4B

In general steers masticated the hay and silage similarly with similar median particle size (mean = 1.5 mm) of the whole masticate (Table 4.4). This similarity among treatments is further demonstrated when we examine the cumulative percentages of oversize dry matter particles from the masticate and the particle sizes of the feces dry matter (Fig. 4.1). The IVDMD of the hay masticate was greater compared with that of the silages, while the neutral detergent fiber concentrations of hay and silages were similar. For hay, the large particle-size class accounted for 61.6% of the masticate dry matter, followed by 30.8% for medium particles and 7.6% for small particles, and no differences in these proportions were noted among treatments. The greater in vitro dry matter disappearance of whole-masticate hay was evident in the large particle-size class, with hay again having greater in vitro dry matter disappearance than silage.

Some measurements of chewing behavior were obtained during the masticate experiment. The average dry matter per bolus was generally similar between hay and the wilted silage, with the direct-cut silage having the least (Table 4.5). Dry matter contained grams in each bolus was similar, but varied considerably, whereas the number of chews per bolus differed. Hay and the wilted silage required similar numbers of chews, with direct-cut silage requiring the least chews. This was also noted for chewing time (seconds per bolus). All treatments were similar in number of chews per gram of dry matter or gram of neutral detergent fiber.

Summary and Conclusions

Switchgrass regrowth cut at the heading stage and either directly ensiled (26% dry matter) or wilted (45% dry matter) fermented well with pH below 4.8.
Steers consumed more hay than silage and more wilted silage than they did direct-cut silage.
Dry matter digestibility measures of hay and direct-cut silage were similar and greater than those of wilted silage, but digestible intakes reflect dry matter intake.
Silage, as a preservation method, can be used for switchgrass regrowth and can be a component of an animal production system.

Table 4.1. Fermentation characteristics of regrowth switchgrass silage when ensiled in the headed stage, Experiments 4A and 4B (dry matter basis).
Treatment	DM¹	pH	Alcohol		Fatty Acids
	DM¹		Ethanol	Methanol	Acetic	Propionic	Lactic	Butyric
	%		————————————% ————————————
Direct Cut (DC)	26.3²	3.8	0.35	—	0.87	0.05	7.8	0.03
Wilted (WT)	45.6	4.7	0.31	0.05	0.48	0.03	2.2	0.57
SD³	11.2	0.5	0.05	0.07	0.23	0.03	3.2	0.32

¹ DM = dry matter.

² Each value is the mean of four samples.

³ SD = standard deviation.

Table 4.2. Dry matter (DM) intake (DMI), digestibility, and digestible intakes of DM and associated nutritive value¹ of headed, regrowth switchgrass preserved as hay or silage, Experiment 4A (DM basis).
Treatment	DMI	Digestibility					Digestible Intake
	DMI	DM	NDF	ADF	HEMI	CELL	DM	NDF	ADF	HEMI	CELL
	lb/100 lb²	————————% ————————					———————lb/100 lb ——————
Hay (H)	1.94³	58.0	59.3	55.7	63.7	62.9	1.12	0.82	0.42	0.40	0.39
Silage (S):
Direct Cut (DC)	1.21	59.0	60.2	58.1	63.1	65.7	0.71	0.52	0.30	0.23	0.28
Wilted (WT)	1.79	51.4	53.1	50.9	56.2	58.6	0.92	0.69	0.39	0.30	0.37
Significance (P):
Treatment	<0.01	0.06	0.08	0.08	0.10	0.06	<0.01	<0.01	0.01	<0.01	<0.01
H vs. S	<0.01	0.25	0.27	0.58	0.17	0.68	<0.01	<0.01	0.01	<0.01	0.01
DC vs. WT	<0.01	0.03	0.04	0.03	0.07	0.03	0.01	0.01	0.01	0.02	0.01
MSD⁴	0.23	6.8	7.0	6.5	8.0	5.9	0.15	0.11	0.06	0.06	0.05

¹ NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Body weight basis.

³ Each value is the mean of four steers.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 4.3. In vitro dry matter disappearance (IVDMD) and nutritive value¹ of as-fed (AF) headed, regrowth switchgrass preserved as hay and silage, Experiment 4A (dry matter basis).
Treatment	IVDMD		CP		NDF		Fiber Fractions
	AF	DV²	AF	DV	AF	DV	ADF	HEMI	CELL	Lignin
	—————————————————%——————————————————
Hay (H)	50.8³	-5.8	9.2	-2.6	71.1	1.6	39.1	32.1	32.4	6.0
Silage (S):
Direct Cut (DC)	48.8	-8.9	7.5	0.0	72.4	0.6	42.4	30.0	35.0	6.4
Wilted (WT)	48.3	0.1	7.9	0.2	72.6	0.7	42.6	30.0	35.6	6.5
Significance (P):
Treatment	0.48	0.47	<0.01	<0.01	0.01	0.20	<0.01	<0.01	<0.01	<0.01
H vs. S	0.26	0.82	<0.01	<0.01	<0.01	0.09	<0.01	<0.01	<0.01	<0.01
DC vs. WT	0.81	0.25	0.04	0.55	0.48	0.75	0.02	0.96	0.02	0.01
MSD⁴	5.7	19.1	0.4	0.9	0.7	1.5	0.6	0.2	0.5	0.1

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² DV = difference value (weighback concentration minus AF concentration).

³ Each value is the mean of four samples.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 4.4. Whole-masticate median particle size (MPS), particle-size classes¹, and associated nutritive value² of headed, regrowth switchgrass preserved as hay and silage, Experiment 4B (dry matter basis).
Treatment	Whole Masticate			Particle-size Classes
	Whole Masticate			Large			Medium			Small
	MPS	IVTD	NDF	Prop³	IVTD	NDF	Prop	IVTD	NDF	Prop	IVTD	NDF
	mm	—————————————————— % ——————————————————
Hay (H)	1.5⁴	58.4	70.7	61.6	56.9	71.9	30.9	60.1	69.6	7.5	63.3	66.2
Silage (S):
Direct Cut (DC)	1.5	51.6	70.2	58.4	49.3	72.2	33.2	54.3	68.7	8.4	58.2	63.0
Wilted (WT)	1.6	52.2	71.0	64.9	50.9	72.6	28.3	53.2	69.5	6.8	59.2	62.7
Significance (P):
Treatment	0.46	0.03	0.71	0.39	<0.01	0.72	0.16	0.13	0.66	0.64	0.32	0.44
H vs. S	0.90	0.01	0.87	0.99	<0.01	0.56	0.90	0.07	0.57	0.91	0.18	0.25
DC vs. WT	0.26	0.60	0.47	0.16	0.04	0.63	0.09	0.65	0.53	0.41	0.76	0.93
MSD⁵	0.28	3.9	2.6	10.2	1.9	2.4	5.6	7.6	3.1	4.8	8.9	7.9

¹Large = > 1.7mm; medium = ≤1.7mm and >0.5mm; small < 0.5 mm.

² IVTD = in vitro true dry matter disappearance; NDF = neutral detergent fiber.

³Prop = proportion of dry matter.

⁴ Each value is the mean of three steers.

⁵ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 4.5. Bolus characteristics and chewing behavior of steers fed headed, regrowth switchgrass preserved as hay and silage, Experiment 4B (dry matter basis).
Treatment	Bolus		Chews
	DM¹	Weight	Number	Sec²	per g DM	per g NDF³
	%	grams	——per bolus——		No.	No.
Hay (H)	16.8⁴	20.2	30.3	24.2	1.5	2.1
Silage (S):
Direct Cut (DC)	13.2	13.2	17.5	14.9	1.4	2.0
Wilted (WT)	16.6	19.9	29.3	22.3	1.5	2.1
Significance (P):
Treatment	0.03	0.19	<0.01	0.01	0.97	0.98
H vs. S	0.06	0.27	0.01	0.01	0.93	0.94
DC vs. WT	0.02	0.13	<0.01	0.01	0.84	0.88

¹ DM = dry matter.

² Sec = seconds.

³NDF = neutral detergent fiber.

⁴ Each value is the mean of three steers.

Figure 4.1. Particle size distribution of dry matter of masticate (closed symbols) and subsequent feces (open symbols) from headed regrowth switchgrass hay (●,○), direct-cut silage (◼︎,◻︎) and wilted silage(▲,△).

Section II. Gamagrass

Experiment 5. Gamagrass Preserved as Hay, Baleage, and Silage: Ensiling Characteristics, Nutritive Value, and Quality

Experiment 6. Gamagrass Preserved as Direct-Cut Baleage, Wilted Baleage, Silage, and Hay: Ensiling Characteristics, Nutritive Value and Quality

Experiment 7. Potential Benefits from Inoculating Gamagrass Forage Prior to its Preservation as Baleage

Experiment 8. Gamagrass Preserved as Hay and Silage and Compared with Silages of a Temperate and Tropical Corn: Nutritive Value and Quality

Experiment 5. Gamagrass Preserved as Hay, Baleage, and Silage: Ensiling Characteristics, Nutritive Value, and Quality

Our objective in this experiment was to assess and compare the nutritive value and quality of gamagrass preserved as, hay (field-cured and baled), baleage (direct-cut or wilted), or direct-cut silage.

Materials and Methods

A well-established stand of Iuka eastern gamagrass provided the experimental forage. The field was burned off in early February to remove all carry-over fall growth and topdressed in mid-February with 70 pounds of nitrogen per acre. The field was cut May 16 with gamagrass in the vegetative stage, and the following four preservation treatments were evaluated:

Hay: cut, field cured, square baled as hay
Baleage, direct-cut: cut, directly round-baled, wrapped for baleage
Baleage, wilted: cut, wilted, round-baled, wrapped for baleage
Silage, direct-cut: cut, directly chopped with field chopper, ensiled

All forage was cut with a mower-conditioner set to a 4-inch stubble. The forage to be made as direct-cut baleage was immediately round-baled and wrapped (Appendix GP-2). Baling and wrapping of the wilted forage occurred about four hours after cutting. All baleage was wrapped with four layers of plastic and stored outside until fed the following fall. Forage preserved as silage was picked up from a direct-cut windrow by a field chopper, blown into a self-unloading wagon, and elevated into an upright fiberglass silo lined with plastic. The forage was treaded at filling to exclude oxygen, and the top of the plastic liner tied off at completion of filling (Appendix GP-2). The forage cut for hay was field cured, being tedded daily to aid drying, and square-baled when dry. The bales were placed (Appendix GP-1) on wooden pallets in the experimental hay barn at the NC State University Forage-Animal Metabolism Unit, Raleigh, NC, until fed.

Two experiments were conducted. One experiment (Experiment 5A) evaluated dry matter intake and digestibility, and the second (Experiment 5B) evaluated masticate characteristics. The intake and digestibility experiment was conducted as a randomized complete block design with four replicates. The 16 steers (mean weight = 575 ± 69.2 pounds) were grouped by fours based on similar weight and assigned at random to the four treatments within each replicate. Intake and digestibility measurements were obtained using normal procedures (Appendix GP-3). Steers were fed at an average of 14.3% excess.

The mastication experiment (Experiment 5B) was also conducted as a randomized complete block design with five esophageal-cannulated steers per treatment. The animals were randomized and assigned to a forage treatment and each steer fed two treatments on day one and two treatments on day two. Sample collection, processing, and particle size determination were conducted according to normal procedures (Appendices GP-4 and GP-5).

All as-fed hay, weighback, and masticate samples were analyzed for nutritive value, and fecal samples were analyzed for chemical composition, according to normal procedures (Appendix GP-6). The data were statistically analyzed according to the experimental design (Appendix GP-7).

Results and Discussion

Examination of the fermented gamagrass reveals that the baleage treatments produced differences in dry matter, with dry matter concentrations greater (P = 0.07) for the wilted compared with the direct cut. Both baleage treatments had greater dry matter concentrations than the silage (Table 5.1). Fermentation characteristics varied among the fermented treatments, although pH and methanol concentrations were similar. Direct-cut baleage had greater concentrations of ethanol and butyric acid and lesser concentrations of lactic acid than wilted baleage.

Comparing the baleage treatments with silage, baleage was greater in dry matter (24.7% versus 18.9 % for silage) and lactic acid, but lesser in propionic, butyric, and isobutyric acids. Sufficient fermentation had occurred for all forages as noted by pH values (Table 5.1).

Experiment 5A

Dry matter intake of hay and its digestibility were both similar to that of baleage and silage (Table 5.2). Steers, however, digested greater neutral detergent fiber from hay compared with the other treatments. This was also noted for hemicellulose digestibility and is reflected in digestible intakes of the two (Table 5.2).

The baleage differed in dry matter digestibility, with the wilted (61.5%) greater than the direct cut (54.7%). This was also noted for neutral detergent fiber and hemicellulose (Table 5.2). Of the fermented forages, baleage was consumed in greater amounts than was silage (2.07 versus 1.59 pounds/100 pounds body weight), and hemicellulose and cellulose were more digestible in silage than in baleage.

Steers apparently processed the hay somewhat differently compared with the fermented treatments. Neutral detergent fiber, acid detergent fiber, and lignin concentrations of the feces were lesser for hay compared with those of the other treatments (Table 5.3). This may, in part, be attributed to the changes that occur in the soluble constituents of gamagrass during fermentation (production of volatile fatty acids).

The composition of the as-fed forages differed, with hay averaging greater in in vitro true dry matter disappearance and neutral detergent fiber concentration, but lesser concentrations of the other fiber constituents compared with those of the other treatments (Table 5.4). The two baleage treatments were similar in nutritive value, whereas the baleage and silage values differed. Silage had greater in vitro true dry matter disappearance, neutral detergent fiber and hemicellulose, but lesser concentrations of lignin (Table 5.4). Some selective consumption occurred as noted by the magnitude of the difference values (weighback concentration minus as-fed concentration). Concentrations of crude protein and neutral detergent fiber were greater for hay compared to other treatments, indicating steers were more selective when consuming the hay treatment. Also, more selectivity occurred for silage compared to baleage, with greater difference values for in vitro true dry matter disappearance and neutral detergent fiber.

Experiment 5B

The whole masticate selected from the as-fed hay was greater in dry matter and in median particle size, as well as in in vitro true dry matter disappearance, crude protein, and neutral detergent fiber, compared with masticate from the fermented treatments. Also, masticate from the two baleage treatments differed, with the wilted baleage having greater median particle size, in vitro true dry matter disappearance, and neutral detergent fiber. Masticate from baleage had greater dry matter compared with that from silage, indicating less incorporation of saliva during ingestion.

Particle size distribution indicates that hay had the greatest proportion of masticate dry matter in large particles (54.6%), being greater compared with that of the fermented forage, with a similar proportion of medium particles and the least proportion of small particles (Table 5.5). Within the particle-size classes, hay generally had greatest in vitro true dry matter disappearance and neutral detergent fiber concentration compared with the fermented treatments, but with similar crude protein concentrations. The baleage and silage treatments varied some in proportions of dry matter and nutritive value, but differences were generally small (Table 5.5).

Summary and Conclusions

Gamagrass was readily cured as hay and consumed by steers, averaging 2.19 pounds per 100 pounds of body weight.
Gamagrass can be baled green and preserved as baleage, either when direct cut or when wilted, and it fermented sufficiently (pH 4.8 – 5.1) to give a stable silage
Gamagrass preserved as baleage had dry matter intakes of 2.05 to 2.08 pounds per 100 pounds of body weight when baled as direct cut or if wilted.
Dry matter digestibility of hay, wilted baleage, and direct-cut silage were all greater compared with that of the direct-cut baleage.
Masticate characteristics indicated that steers incorporated more saliva into ingested hays, which also had greater concentrations of in vitro true dry matter disappearance, crude protein, and neutral detergent fiber.
Gamagrass can be managed as a hay or preserved as baleage or silage and contribute to animal production systems in the Upper South.

Table 5.1. Dry matter (DM) concentration and fermentation characteristics of gamagrass preserved as baleage and silage, Experiments 5A and 5B (DM basis).
Treatment	DM	pH	Alcohol		Fatty Acids
	DM		Ethanol	Methanol	Acetic	Propionic	Lactic	Butyric	Isobutyric
	%		——————————————— % ———————————————
Baleage (B):
Direct Cut (DC)	22.7¹	5.1	1.43	0.07	3.13	0.17	0.80	1.83	0.03
Wilted (WT)	26.8	4.8	0.39	0.03	2.37	0.09	2.14	0.71	0.01
Silage (S)	18.9	4.8	0.59	0.06	4.55	0.52	0.05	4.48	0.07
Significance (P):
Treatment	0.02	0.34	0.08	0.15	0.02	<0.01	0.01	<0.01	0.03
DC vs. WT	0.07	0.20	0.04	0.07	0.20	0.24	0.02	0.04	0.22
B vs. S	0.01	0.48	0.40	0.56	0.01	<0.01	0.01	<0.01	0.01
MSD²	4.7	0.54	1.03	0.04	1.31	0.13	1.00	1.02	0.04

¹ Each value is the mean of four samples.

² MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 5.2. Dry matter (DM) intake (DMI), digestibility, and digestible intakes of DM and associated nutritive value¹ of gamagrass preserved as hay, baleage, and silage, Experiment 5A (DM basis).
Treatment	DMI	Digestibility					Digestible Intake
	DMI	DM	NDF	ADF	HEMI	CELL	DM	NDF	ADF	HEMI	CELL
	lb/100 lb²	————————%———————					——————— lb/100 lb ——————
Hay (H)	2.19³	61.6	67.4	65.2	63.4	70.0	1.35	1.06	0.49	0.58	0.47
Baleage (B):
Direct Cut (DC)	2.05	54.7	57.1	64.1	45.5	69.3	1.13	0.82	0.56	0.25	0.52
Wilted (WT)	2.08	61.5	62.6	67.6	55.0	72.7	1.28	0.89	0.57	0.32	0.53
Silage (S)	1.59	61.8	64.2	67.6	59.6	75.5	0.99	0.72	0.44	0.28	0.44
Significance (P):
Treatment	0.14	0.05	0.01	0.30	<0.01	0.06	0.18	0.08	0.20	<0.01	0.47
H vs. Others	0.20	0.29	0.01	0.47	<0.01	0.19	0.13	0.03	0.51	<0.01	0.61
DC vs. WT	0.89	0.02	0.04	0.13	<0.01	0.14	0.38	0.54	0.84	0.29	0.86
B vs. S	0.05	0.12	0.06	0.36	<0.01	0.04	0.15	0.22	0.05	0.85	0.15
MSD⁴	0.63	6.0	5.3	5.4	6.3	5.3	0.41	0.29	0.16	0.12	0.17

¹ NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Body weight basis.

³ Each value is the mean of four steers.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 5.3. Chemical composition¹ of feces from steers fed gamagrass preserved as hay, baleage, and silage, Experiment 5A (dry matter basis).
Treatment	CP	NDF	Fiber fractions
	CP	NDF	ADF	HEMI	CELL	Lignin
	—————————— % ——————————
Hay (H)	12.4²	61.1	30.7	30.4	23.4	7.2
Baleage (B):
Direct Cut (DC)	12.1	66.1	34.4	31.7	25.3	8.4
Wilted (WT)	13.4	64.7	33.7	30.9	24.1	8.5
Silage (S)	12.3	66.0	34.9	31.1	23.5	9.1
Significance (P):
Treatment	0.21	0.01	<0.01	0.42	0.33	0.01
H vs. Others	0.70	<0.01	<0.01	0.20	0.33	<0.01
DC vs. WT	0.06	0.28	0.35	0.33	0.28	0.92
B vs. S	0.46	0.59	0.21	0.72	0.24	0.11
MSD³	1.7	3.0	1.6	2.0	2.9	1.0

¹ NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Each value is the mean of four steers.

³ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100)

t-test and can be used to compare any two treatments.

Table 5.4. In vitro true dry matter disappearance (IVTD) and nutritive value¹of as-fed (AF) gamagrass preserved as hay, baleage, and silage, Experiment 5A (dry matter basis).
Treatment	IVTD		CP		NDF		Fiber fractions
	AF	DV²	AF	DV	AF	DV	ADF	HEMI	CELL	Lignin
	—————————————————%—————————————————
Hay (H)	70.3³	-3.6	12.6	-4.0	72.8	2.4	35.2	37.6	31.3	3.9
Baleage (B):
Direct Cut (DC)	64.0	-0.4	12.3	0.1	69.2	0.3	42.7	26.6	36.4	5.2
Wilted (WT)	66.2	-0.2	12.5	-0.3	68.5	-0.2	40.8	27.7	35.0	5.1
Silage (S)	69.4	-3.8	12.6	-1.1	70.6	2.0	41.3	29.3	36.5	4.6
Significance (P):
Treatment	<0.01	0.08	0.91	<0.01	<0.01	0.05	<0.01	<0.01	<0.01	<0.01
H vs. Others	0.01	0.13	0.72	<0.01	<0.01	0.05	<0.01	<0.01	<0.01	<0.01
DC vs. WT	0.11	0.92	0.65	0.50	0.22	0.58	0.09	0.16	0.09	0.62
B vs. S	<0.01	0.03	0.69	0.10	0.01	0.04	0.65	0.01	0.20	<0.01
MSD⁴	2.8	4.0	1.4	1.3	1.2	2.2	2.2	1.6	1.6	0.3

¹CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² DV = difference value (weighback concentration minus AF concentration).

³Each value is the mean of four samples.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 5.5. Whole-masticate dry matter (DM), median particle size (MPS), and particle-size classes¹ and associated nutritive value² of gamagrass preserved as hay, baleage, and silage, Experiment 5B (DM basis).

Treatment	Whole Masticate					Particle-size Classes
	Whole Masticate					Large				Medium				Small
	DM	MPS	IVTD	CP	NDF	Prop³	IVTD	CP	NDF	Prop	IVTD	CP	NDF	Prop	IVTD	CP	NDF
	%	mm	——————————————————————%——————————————————————————
Hay (H)	16.9⁴	2.0	78.4	12.7	67.1	54.6	73.6	10.0	70.1	37.1	79.4	13.5	66.9	8.3	82.6	14.3	62.7
Baleage (B):
Direct Cut (DC)	11.6	0.9	67.2	11.3	62.9	22.5	66.5	10.8	63.9	49.1	66.1	10.4	64.2	28.4	70.0	13.0	61.1
Wilted (WT)	12.6	1.7	71.2	11.4	65.3	45.9	68.8	10.3	66.6	40.7	72.7	12.2	63.6	13.4	74.8	13.3	60.9
Silage (S)	8.5	1.6	67.9	10.9	62.7	47.1	66.3	10.2	64.4	40.7	66.9	10.3	61.8	12.2	74.8	14.3	58.1
Significance (P):
Treatment	<0.01	<0.01	<0.01	0.09	<0.01	<0.01	<0.01	0.13	<0.01	0.07	<0.01	<0.01	<0.01	<0.01	<0.01	0.05	0.03
H vs. Others	<0.01	0.01	<0.01	0.02	<0.01	0.01	<0.01	0.09	<0.01	0.08	<0.01	<0.01	<0.01	<0.01	<0.01	0.09	0.03
DC vs. WT	0.11	0.01	<0.01	0.85	0.02	<0.01	<0.01	0.19	<0.01	0.06	<0.01	<0.01	0.44	<0.01	<0.01	0.50	0.93
B vs. S	<0.01	0.19	0.22	0.48	0.09	0.03	0.02	0.22	0.17	0.25	<0.01	0.02	0.87	<0.01	0.03	0.03	0.03
MSD⁵	1.1	0.5	2.3	1.6	1.9	13.3	1.2	0.8	1.4	9.8	1.5	0.9	1.5	5.7	2.2	1.2	3.0

¹ Large = > 1.7mm; medium = ≤1.7mm and >0.5mm; small < 0.5 mm.

² IVTD = in vitro true dry matter disappearance; CP = crude protein; NDF = neutral detergent fiber.

³ Prop = proportion of dry matter.

⁴Each value is the mean of five steers.

⁵ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Experiment 6. Gamagrass Preserved as Direct-Cut Baleage, Wilted Baleage, Silage, and Hay: Ensiling Characteristics, Nutritive Va

Our objective in these experiments was to assess and compare the ensiling characteristics, nutritive value, and quality of gamagrass when preserved as field-cured hay, baleage (direct-cut or wilted), and silage (direct-cut forage ensiled in either an upright silo or a sausage-bag silo).

Materials and Methods

A well-established stand of Iuka gamagrass provided the experimental forages. The field was burned in late February to remove all fall-carryover growth and topdressed in mid-March with 80 pounds of nitrogen per acre. The forage was cut June 2 in the early-heading stage and used in Experiment 6A. After harvest, the stand was again topdressed with 80 pounds of nitrogen per acre. The regrowth forage was cut August 10 and used in Experiment 6B. The treatments for each experiment were as follows:

Experiment 6A (Initial growth)

Hay, field cured
Baleage, direct cut
Baleage, wilted
Silage (upright silo)

Experiment 6B (Regrowth)

Hay, field cured
Baleage, direct cut
Baleage, wilted
Silage (sausage-bag silo)

Forage for all treatments was cut with a mower-conditioner set to leave a 5-inch stubble. The forage preserved as baleage—whether direct-cut or wilted—was baled in a big-round baler, wrapped four times with white plastic, and placed on the ground until fed the following fall (Appendix GP-2). The forage preserved as silage was picked up with a field chopper, blown into a self-unloading wagon, and transported and stored in either an upright experimental silo (Experiment 6A) or a sausage-bag silo (Experiment 6B) and permitted to ferment until fed in the fall (Appendix GP-2). Forage that was field cured as hay was baled when dry with a conventional square baler, transported to the NC State University Forage-Animal Metabolism Unit, Raleigh, NC, and stored on wooden pallets in an experimental hay barn until fed. Prior to feeding, the hay and the fermented forages were processed according to normal protocol (Appendices GP-1 and GP-2).

Two experiments—an intake-and-digestibility experiment and a masticate experiment—were conducted within each of Experiment 6A and Experiment 6B. Both intake and digestibility experiments were conducted as a randomized complete block design with four steers (replicates) per treatment (mean weight = 591 ± 37 pounds) in Experiment 6A and five steers per treatment (mean weight = 667 ± 37 pounds) in Experiment 6B. Steers in Experiment 6A were fed at 12.5% excess and steers in Exp 6B at 13% excess. Both experiments were conducted according to normal procedures (Appendix GP-3).

The masticate experiments were also conducted in a randomized complete block design with five steers (replicates) per treatment. The masticate collection, processing, and particle size determination were conducted according to normal procedures (Appendices GP-4 and GP-5).

All as-fed hay, weighback, and masticate samples were analyzed for nutritive value, and fecal samples were analyzed for chemical composition, according to normal procedures (Appendix GP-6). The data were statistically analyzed according to the experimental design (Appendix GP-7). Because of inadequate forage or animal complications (off feed), we could not evaluate all treatments with all animals. Consequently, the number (n) of animals for which we could evaluate the various treatment variables has been designated as a footnote in each table.

Results and Discussion

Experiment 6A

Fermentation characteristics. Dry matter at feeding was greater (P = 0.04) for gamagrass baleage than for silage and associated with the greater (P = 0.06) DM of the wilted compared with the direct-cut baleage (49.4 versus 40.5, Table 6.1). All three treatments fermented well with a pH of 5.6 or less. The least pH occurred for gamagrass preserved as silage, averaging 4.5 and lesser (P = 0.01) than the 5.6 noted for the baleages. Consistent with pH, silage produced greater concentrations of propionic, lactic, and butyric acid compared with the baleages.

Intake and digestibility. Steers consumed the least (P = 0.05) hay compared with the mean of the baleages and silage (Table 6.2). Further, steers consumed the baleages similarly and consumed greater amounts of baleage than silage. The dry matter digestibilities of all four treatments were similar, averaging 61.1%. No differences were noted in neither the digestibilities nor in the digestible intakes of dry matter and fiber fractions among the preservation methods.

Examination of the as-fed forages indicates that gamagrass made as hay was generally greater in nutritive value, being greater in in vitro true dry matter disappearance (P = 0.01) and lesser (P = 0.02) in neutral detergent fiber and the other fiber constituents (except hemicellulose) than the ensiled treatments (Table 6.3). Also, baleage was generally greater in CP and lesser in neutral detergent fiber compared with silage. However, most differences were relatively small and probably of little biological importance. This is consistent, with no difference evident among preservation methods in digestibility of dry matter and nutritive value variables (Table 6.2). Some selective consumption was apparent as indicated by the magnitude of the difference value (weighback concentration minus as-fed concentration) being greatest for the hay and baleage treatments and least for silage. This is, in part, attributed to some degree of a finer chop for the silage treatment compared with the others.

Feces composition reveals some differences in method of preservation. Fecal samples from hay were lesser (P < 0.01) in neutral detergent fiber and its constituents hemicellulose and cellulose (Table 6.4) than samples from the baleage and silage. Also, fecal samples from baleage were generally greater (P= 0.02) in crude protein and lesser (P = 0.02) in acid detergent fiber than samples from silage, with no difference in composition between the samples from baleage treatments.

Mastication characteristics. The dry matter of the whole masticate was similar among preservation methods, indicating that steers incorporated relatively more saliva into the hay and baleage treatments compared with the silage (Table 6.5). Animals chewed the four forages similarly, with a mean particle size of 1.55 mm.

Compared with the ensiled gamagrass, hay was greater (P = 0.01) in in vitro true dry matter disappearance and neutral detergent fiber and lesser in CP (Table 6.5). Also, baleage was greater in in vitro true dry matter disappearance and crude protein than was silage. Further, wilted baleage had a greater concentration of CP than did direct-cut gamagrass.

Separating the masticate into particle-size classes revealed 42.7% large, 45.5% medium, and 11.9% small particles. No difference was noted among treatments in the proportion of large particles (mean = 42.7), but hay had a greater (P < 0.01) proportion of medium particles. Also, the baleage treatments had a greater proportion of small particles than did silage. These differences are more easily viewed in figure format giving dry matter distribution among sieve sizes (Figure 6.1, Experiment 6A). Some differences were noted in nutritive value among preservation methods within each particle-size class, but these differences were generally small.

Experiment 6B

Fermentation characteristics. Dry matter of the preserved forages was greatest (P < 0.01) for the baleage treatments and least for silage (Lower portion, Table 6.1). Also, dry matter of the wilted baleage was greater (P < 0.01) compared with that of the direct-cut baleage. In this experiment, fermentation of the baleage treatments was very limited, with pH levels of 7.5 to 7.7. The pH levels of baleage treatments were similar and greater (P < 0.02) than that of the silage, which was favorable at a pH of 4.7. The major fermentation difference between baleage and silage was the greater (P < 0.01) concentration of lactic acid in the silage.

Intake and digestibility. Steers consumed hay the most (P < 0.01) compared with the baleage and sausage-bag silage treatments, with essentially no difference in intake among baled forages (Table 6.2). Because of a lack of silage, it was dropped from the digestibility phase of the experiment.

Consequently, we compared only the digestibility estimates of hay and the two baleage treatments. Digestibilities of dry matter and fiber fractions were similar among the treatments with digestible intakes of dry matter and hemicellulose greater (P < 0.04) for hay compared with baleage intakes. Silage from neither the direct-cut nor the wilted treatments altered digestibilities or digestible intakes of dry matter and hemicellulose greater (P < 0.04) for hay compared with baleage intakes. Silage from neither the direct-cut nor the wilted treatments altered digestibilities or digestible intakes.

The as-fed hay was greater (P < 0.01) in in vitro true dry matter disappearance and crude protein compared with the fermented treatments (Table 6.3). In general, baleage and silage were similar in nutritive value. The exception was neutral detergent fiber, for which baleage averaged a greater concentration than silage (P = 0.01).

In this experiment no differences were noted in feces composition among the hay and two baleage treatments (Table 6.4).

Masticate characteristics. Steers differentially incorporated saliva into the masticated forage, with greater saliva incorporated into hay. But the dry matter concentration of the hay still remained greater (P < 0.01) compared with that of the ensiled treatments (Table 6.5). Also, steers masticated the direct-cut baleage greater (P = 0.01) than the wilted baleage. The whole masticate of the hay was greater in in vitro true dry matter disappearance (P = 0.04) and neutral detergent fiber (P = 0.03) and lesser (P = 0.03) in crude protein compared with the masticate from the ensiled treatments. Also, baleage was greater in in vitro true dry matter disappearance and neutral detergent fiber (P = 0.02) than was silage. Within the baleages, the wilted had greater (P < 0.01) in vitro true dry matter disappearance and crude protein concentration than the direct cut.

The masticate dry matter consisted of 43.6% large particles, 43.6% medium particles, and 12.8% small particles, with some differences noted among treatments within each class. Hay had a greater (P < 0.01) proportion of medium particles compared to the fermented treatments. Also, the wilted baleage had a greater proportion of large particles and a lesser proportion of medium and small particles compared with the direct-cut baleage. The overall distribution of masticate dry matter among sieve sizes is presented for ease of viewing (Figure 6.1, Experiment 6B). Differences were also noted in nutritive value among the preservation methods in each particle-size class (Table 6.5).

Summary and Conclusions

1. Gamagrass can be preserved as hay, direct-cut or wilted baleage, or as silage.

2. Gamagrass fermented well, with a pH of 4.7 or less when ensiled in an upright silo or placed in a sausage-bag silo.

3. Preservation as baleage varied appreciably, with some fermentation (pH 5.6) occurring in Experiment 6A and essentially no fermentation (pH 7.6) in Experiment 6B.

4. Steers consumed baleage well in Experiment 6A at 2.59 pounds per 100 pounds of body weight and greater than hay (2.15 lb per 100 lb body weight), which was similar to silage (2.18 lb per 100 lb body weight), and steers digested the dry matter similarly (61.1%).

5. Steers consumed more hay than ensiled forage in Experiment 6B, averaging 2.58 pounds per 100 pounds of body weight versus 1.84 for the fermented treatments, and again digested the dry matter similarly (59.8%) as in Experiment 6A.

Table 6.1. Ensiling characteristics of gamagrass when preserved as baleage and silage, Experiment 6A and 6B (dry matter basis).
Treatment	DM¹	pH	Alcohol		Fatty Acids
	DM¹		Ethanol	Methanol	Acetic	Propionic	Lactic	Butyric	Isobutyric
	%		———————————————%————————————————
Experiment 6A:
Baleage (BL):
Direct Cut (DC)²	40.5	5.6	0.14	0.02	0.59	0.03	0.81	0.11	0.02
Wilted (WT)³	49.4	5.6	0.09	0.01	0.35	0.02	0.55	0.06	0.02
Silo Silage (SS)⁴	36.8	4.5	0.08	0.02	0.62	0.08	2.45	0.22	0.02
Significance (P):
Treatment	0.03	0.01	0.11	0.27	0.36	0.03	<0.01	0.09	0.13
BL vs. SS	0.04	0.01	0.14	0.27	0.40	0.01	<0.01	0.05	0.09
DC vs. WT	0.06	0.89	0.07	0.27	0.30	0.72	0.20	0.46	0.31
Experiment 6B:
Baleage (BL):
Direct Cut (DC)⁵	43.2	7.5	0.02	0.02	0.07	—	0.17	0.02	0.02
Wilted (WT)⁵	56.7	7.7	0.03	0.01	0.07	—	0.07	0.01	0.01
Sausage Silo (SA)⁶	37.1	4.7	0.03	0.03	0.12	0.02	2.41	0.02	0.02
Significance (P):
Treatment	<0.01	<0.01	0.24	0.10	0.19	0.18	<0.01	0.26	0.17
BL vs. SA	<0.01	<0.01	0.29	0.05	0.08	0.08	<0.01	0.32	0.45
DC vs. WT	<0.01	0.45	0.18	0.43	0.98	—	0.43	0.18	0.09

¹ DM = dry matter.

² Each value is the mean of three samples.

³Each value is the mean of four samples.

⁴ Each value is the mean of six samples.

⁵ Each value is the mean of five samples.

⁶ Each value is the mean of two samples.

Table 6.2. Dry matter (DM) intake (DMI), digestibility, and digestible intakes of DM and associated nutritive value¹ of Iuka gamagrass preserved as hay and silages, Experiment 6A and 6B (DM basis).
Treatment	DMI	Digestibility					Digestible Intake
	DMI	DM	NDF	ADF	HEMI	CELL	DM	NDF	ADF	HEMI	CELL
	lb/100 lb²	————————% ————————					——————lb/100 lb ——————
Experiment 6A:
Hay³	2.15	59.3	65.7	63.5	67.6	69.4	1.23	0.97	0.46	0.51	0.45
Baleage (BL):
Direct Cut (DC)⁴	2.86	62.3	64.9	64.6	65.2	70.3	1.79	1.32	0.71	0.61	0.67
Wilted (WT)⁵	2.32	62.1	64.3	64.8	63.7	69.9	1.37	0.99	0.52	0.47	0.48
Silo Silage (SS)⁵	2.18	60.6	62.7	63.7	61.6	69.1	1.40	1.01	0.56	0.45	0.52
Significance (P):
Treatment	0.02	0.47	0.64	0.92	0.18	0.97	0.16	0.24	0.17	0.22	0.18
Hay vs. Others	0.05	0.20	0.41	0.67	0.08	0.85	0.10	0.29	0.10	0.99	0.14
BL vs. SS	0.03	0.40	0.40	0.64	0.23	0.67	0.31	0.29	0.46	0.15	0.40
DC vs. WT	0.02	0.94	0.82	0.94	0.59	0.89	0.09	0.09	0.10	0.10	0.08
Experiment 6B:
Hay	2.58⁶	61.34	62.4	60.5	64.1	66.0	1.56	1.10	0.54	0.55	0.51
Baleage (BL):
Direct Cut (DC)	1.95⁶	62.15	66.6	67.4	65.7	70.5	1.20	0.98	0.54	0.44	0.48
Wilted (WT)	1.96⁶	56.13	60.2	60.5	59.9	64.5	1.07	0.85	0.45	0.40	0.41
Sausage Silo (SA)	1.60⁴	—	—	—	—	—	—	—	—	—	—
Significance (P):
Treatment	<0.01	0.25	0.34	0.25	0.41	0.33	0.05	0.12	0.13	0.08	0.11
Hay vs. Others	<0.01	0.53	0.81	0.43	0.76	0.70	0.02	0.09	0.26	0.04	0.12
BL vs. SA	0.10	—	—	—	—	—	—	—	—	—	—
DC vs. WT	0.94	0.13	0.18	0.15	0.22	0.17	0.27	0.18	0.08	0.41	0.10

¹ NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Body weight basis.

³ Each value is the mean of four steers.

⁴ Each value is the mean of two steers.

⁵ Each value is the mean of three steers.

⁶ Each value is the mean of five steers.

Table 6.3. In vitro true dry matter disappearance (IVTD) and nutritive value¹ of as-fed (AF) gamagrass hay, baleage, and silage, Experiment 6A and 6B (dry matter basis).
Treatment	IVTD		CP		NDF		Fiber Fractions
	AF	DV²	AF	DV	AF	DV	ADF	HEMI	CELL	Lignin
	——————————————————%—————————————————
Experiment 6A:
Hay³	69.4	-5.7	9.7	-2.7	71.6	2.1	35.1	36.5	31.2	4.0
Baleage (BL):
Direct Cut (DC)⁴	64.3	-5.5	9.4	-2.5	71.7	3.0	38.1	33.6	33.3	4.8
Wilted (WT)⁵	66.7	-5.9	9.9	-2.5	70.6	2.7	36.9	33.7	31.9	4.6
Silo Silage (SS)³	66.3	-2.1	9.1	-0.6	69.8	0.6	37.9	31.9	32.6	4.8
Significance (P):
Treatment	0.01	0.07	0.06	0.06	<0.01	0.03	<0.01	<0.01	0.01	<0.01
Hay vs. Others	<0.01	0.35	0.44	0.23	0.02	0.99	<0.01	<0.01	<0.01	<0.01
BL vs. SS	0.43	0.03	0.05	0.03	0.01	0.01	0.47	0.01	0.96	0.71
DC vs. WT	0.11	0.80	0.15	0.99	0.06	0.66	0.11	0.81	0.02	0.11
Experiment 6B:
Hay	66.5	-3.7	9.6	-1.4	69.2	2.2	34.5	34.7	30.2	4.0
Baleage (BL):
Direct Cut (DC)⁶	58.9	-5.3	8.4	-0.9	74.1	2.8	40.6	33.6	34.8	5.1
Wilted (WT)⁶	61.4	-2.7	8.7	-0.5	74.3	1.0	39.2	35.1	35.6	5.0
Sausage Silo (SA)⁷	61.6	-1.7	9.4	-0.6	70.1	0.6	38.7	31.5	32.9	4.9
Significance (P):
Treatment	<0.01	0.30	0.05	0.21	<0.01	0.23	<0.01	<0.01	<0.01	<0.01
Hay vs. Others	<0.01	0.75	0.05	0.06	<0.01	0.42	<0.01	0.02	<0.01	<0.01
BL vs. SA	0.41	0.27	0.12	0.87	0.01	0.33	0.19	<0.01	0.06	0.33
DC vs. WT	0.08	0.13	0.39	0.40	0.87	0.09	0.06	0.02	0.03	0.48

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² DV = difference value (weighback concentration minus AF concentration).

³ Each value is the mean of six samples.

⁴ Each value is the mean of three samples.

⁵ Each value is the mean of four samples.

⁶ Each value is the mean of five samples.

⁷ Each value is the mean of two samples.

Table 6.4. Chemical composition¹ of feces from steers fed hay, baleage, and silage of Iuka gamagrass, Experiment 6A and 6B (dry matter basis).
Treatment	CP	NDF	Fiber Fractions
	CP	NDF	ADF	HEMI	CELL	Lignin
	———————————% ———————————
Experiment 6A:
Hay²	11.3	59.9	30.5	29.5	22.6	6.5
Baleage (BL):
Direct Cut (DC)³	11.4	63.1	32.2	30.9	24.0	6.8
Wilted (WT)⁴	10.9	65.6	33.7	31.9	25.3	7.2
Silo Silage (SS)⁴	10.3	66.1	34.7	31.4	25.5	7.3
Significance (P):
Treatment	0.05	<0.01	<0.01	0.02	0.08	0.17
Hay vs. Others	0.17	<0.01	<0.01	0.01	0.03	0.07
BL vs. SS	0.02	0.09	0.02	0.99	0.37	0.37
DC vs. WT	0.19	0.07	0.09	0.14	0.29	0.35
Experiment 6B:
Hay	9.7	65.7	34.1	31.7	26.2	7.0
Baleage (BL):
Direct Cut (DC)⁴	10.9	64.1	33.4	30.7	25.9	7.1
Wilted (WT)²	10.3	65.4	34.1	31.3	26.4	7.1
Sausage Silo (SA)	—	—	—	—	—	—
Significance (P):
Treatment	0.02	0.56	0.74	0.38	0.91	0.65
Hay vs. Others	0.15	0.52	0.76	0.31	0.99	0.47
BL vs. SA	—	—	—	—	—	—
DC vs. WT	0.24	0.42	0.51	0.35	0.69	0.60

¹CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Each value is the mean of four steers.

³ Each value is the mean of two steers.

⁴ Each value is the mean of three steers.

Table 6.5. Whole-masticate dry matter (DM), median particle size (MPS), and particle-size classes¹ and associated nutritive value² of gamagrass preserved as hay, baleage and silage, Experiment 6A and 6B (DM basis).
Treatment	Whole Masticate					Particle-size Classes
	Whole Masticate					Large				Medium				Small
	DM	MPS	IVTD	CP	NDF	Prop³	IVTD	CP	NDF	Prop	IVTD	CP	NDF	Prop	IVTD	CP	NDF
	%	mm	———————————————————————————% ————————————————————
Experiment 6A:⁴
Hay	17.8	1.5	74.1	8.2	67.6	37.5	69.7	6.6	69.7	52.0	75.8	8.9	67.6	10.5	81.4	10.4	60.8
Baleage (BL):
Direct Cut (DC)	17.6	1.5	72.9	8.4	63.8	41.8	68.1	6.7	66.7	44.2	75.1	9.2	63.3	14.0	80.0	10.7	57.8
Wilted (WT)	14.2	1.6	74.1	9.4	64.1	44.3	70.1	8.0	66.7	41.8	75.8	10.1	63.9	13.9	81.2	11.7	55.8
Silo Silage (SS)	14.3	1.6	70.3	8.3	64.2	47.4	67.2	7.3	66.3	43.6	71.9	8.9	63.6	9.0	78.0	10.7	56.3
Significance (P):
Treatment	0.29	0.60	<0.01	<0.01	<0.01	0.16	0.01	<0.01	0.03	0.01	<0.01	0.01	<0.01	0.10	0.02	0.02	0.04
Hay vs. Others	0.24	0.27	0.01	0.02	<0.01	0.06	0.06	0.01	<0.01	<0.01	0.01	0.07	<0.01	0.34	0.07	0.05	0.01
BL vs. SS	0.46	0.74	<0.01	0.01	0.75	0.25	0.01	0.67	0.68	0.77	<0.01	0.02	0.99	0.02	0.01	0.16	0.73
DC vs. WT	0.17	0.50	0.10	<0.01	0.81	0.54	0.01	<0.01	0.97	0.35	0.31	0.01	0.51	0.92	0.24	0.01	0.24
Experiment 6B:
Hay⁴	16.7	1.5	72.7	8.6	65.3	41.8	69.6	7.4	67.8	47.5	74.2	9.2	64.9	10.7	77.5	10.1	56.9
Baleage (BL):
Direct Cut (DC)⁵	13.2	1.4	69.7	8.2	64.7	37.1	65.2	6.6	68.4	46.1	71.0	8.7	64.4	16.8	75.5	10.3	58.1
Wilted (WT)⁴	14.8	1.7	73.6	9.8	63.4	48.6	71.1	8.8	65.8	39.6	74.9	10.3	63.3	11.8	79.0	11.7	55.0
Sausage Silo (SA)⁴	13.1	1.5	69.6	8.9	61.7	47.0	66.2	7.7	64.8	41.1	71.4	9.5	60.3	11.9	75.8	11.1	54.7
Significance (P):
Treatment	0.01	0.05	<0.01	<0.01	0.01	0.01	<0.01	<0.01	0.01	<0.01	<0.01	<0.01	<0.01	0.03	0.02	<0.01	0.31
Hay vs. Others	<0.01	0.55	0.04	0.03	0.03	0.27	0.03	0.21	0.06	<0.01	0.03	0.13	0.01	0.06	0.41	<0.01	0.55
BL vs. SA	0.25	0.77	0.02	0.51	0.02	0.09	0.05	0.98	0.01	0.15	0.07	0.98	<0.01	0.14	0.13	0.51	0.28
DC vs. WT	0.10	0.01	<0.01	<0.01	0.24	<0.01	<0.01	<0.01	0.02	<0.01	<0.01	<0.01	0.27	0.01	0.01	<0.01	0.14

¹ Large = > 1.7mm; medium = ≤1.7mm and >0.5mm; small < 0.5 mm.

² IVTD = in vitro true dry matter disappearance; CP = crude protein; NDF = neutral detergent fiber.

³ Prop = proportion of dry matter.

⁴ Each value is the mean of five steers.

⁵ Each value is the mean of four steers.

Figure 6.1. Particle size distribution of masticate dry matter of gamagrass preserved as hay, baleage [direct cut (DC) or wilted (WT)] and silage [upright silo (UP) in Experiment 6A or sausage-bag silo (SA) in Experiment 6B].

Experiment 7. Potential Benefits from Inoculating Gamagrass Forage Prior to its Preservation as Baleage

Gamagrass, like many warm-season perennial grasses, has a limited concentration of soluble carbohydrates, which reduces its capacity to ferment and produce a stable silage. Sufficient anaerobic fermentation should occur to reduce the silage pH to below 5.0 and better yet to below 4.5. The pH of warm-season grasses frequently stabilizes in the 5.0 to 5.5 range, with the resulting silage unstable and prone to mold. The use of an external silage inoculant may promote further fermentation and increase the nutritive value of the fermented forage. Our objective in this experiment was to assess the effect on intake and digestibility of adding an external inoculant to gamagrass forage to aid fermentation after the forage was either direct cut or wilted and prior to ensiling as baleage.

Materials and Methods

A well-established stand of Iuka eastern gamagrass provided the experimental forage. The regrowth from May 16 was topdressed with 80 pounds of nitrogen per acre and the resulting regrowth cut July 15 with a mower-conditioner set to a 5-inch stubble. The forage was then used to evaluate the following four baleage treatments:

Cut, immediately round-baled, wrapped as baleage
Cut, immediately sprayed with an inoculant, round-baled, wrapped as baleage
Cut, wilted, round-baled, wrapped as baleage
Cut, wilted, sprayed with an inoculant, round-baled, wrapped as baleage

A commercial silage inoculant (Pioneer 1174 silage inoculant, Pioneer Hi-Bred International, Inc., Des Moines, IA) was used and prepared in cool water just prior to application according to directions. All bales received four layers of plastic wrap, were stored outside, and remained undisturbed until time of feeding (March) (Appendix GP-2). At feeding, as bales were transported to the indoor feeding area, the plastic was removed and any surface mold discarded, and each bale ground in an individual round-bale tub-grinder. The ground silage was piled on plastic sheets, by treatment, for feeding and covered with plastic between feeding events (Appendix GP-2).

The intake and digestibility experiment was conducted with steers (mean weight = 611 ± 41 pounds) in a randomized complete block design. The steers were grouped in fours by weight and assigned at random to a treatment within each group (replicate). Animals were fed at 15.6% excess, and the experiment was conducted using normal procedures (Appendix GP-3).

All as-fed hay and weighback samples were analyzed for nutritive value according to normal procedures (Appendix GP-6). The data were statistically analyzed according to the experimental design (Appendix GP-7). Because of little fermentation for the wilted treatments, the interaction of forage treatment (direct cut versus wilted) in relationship to inoculant was frequently significant. Consequently only the minimum significant difference (MSD) is reported for those differences of interest.

Results and Discussion

Our objective in this experiment was predicated on the assumption that both the direct-cut and wilted forage, when preserved as baleage, would undergo fermentation. Upon viewing the fermentation characteristics of the baleage treatments, especially pH, it is evident that the wilted forage fermented little (Table 7.1). This is apparent also from the lack of volatile fatty acid production. Consequently, the influence of the inoculant on fermentation of the wilted forage cannot be evaluated. Several points, however, are worthy of mention. The moisture present in the wilted forage fell below 70%, which is the concentration frequently associated with favorable fermentation. This provides a caution: when cutting gamagrass for baleage, do not delay baling too long after cutting. Baleage from the direct-cut forage did ferment, reducing the pH, with the inoculant resulting in lesser concentrations of ethanol and greater concentrations of the volatile fatty acids. The exception was the lactic acid concentration, which was similar for both the inoculated and uninoculated direct-cut forage.

In this experiment, steer dry matter intake and dry matter digestibility of the direct-cut baleage was not altered by the inoculant. However, differences in the digestibility of the dry matter, neutral detergent fiber, and hemicellulose did approach significance (Table 7.2). Note that the wilted baleage, with or without inoculant, generally had digestibility values similar to those of the direct-cut with inoculant (Table 7.2).

Examination of the nutritive value estimates of as-fed baleage (Table 7.3) generally reflects the digestibility data (Table 7.2). The direct-cut baleage with inoculant is generally greater in nutritive value (greater in vitro dry matter disappearance and crude protein and lesser neutral detergent fiber and its constituent fiber fractions) than direct-cut baleage without inoculant (Table 7.3). Also, the unfermented wilted baleage displayed little difference in nutritive value from preservation with or without inoculant.

Summary and Conclusions

Gamagrass can be preserved as baleage in addition to being grazed or preserved as hay.
Forage with a moisture concentration that declined below 70% did not ferment when preserved as baleage and was prone to mold.
The use of an inoculant for direct-cut baleage with greater than 70% moisture improved nutritive value of the baleage.
Dry matter intake of direct-cut baleage with greater than 70% moisture was not altered by the application of an inoculant, but dry matter digestibility was greater with an inoculant and approached significance.
The use of an inoculant in preserving warm-season perennial grasses, such as gamagrass, as silage (in this case as baleage) may be useful and warrants more critical evaluation.

Table 7.1. Dry matter (DM) concentration and fermentation characteristics of gamagrass preserved as baleage without and with an inoculant (DM basis).
Treatment	DM	pH	Alcohol		Fatty Acids
	DM		Methanol	Ethanol	Acetic	Propionic	Lactic	Butyric	Isobutyric
	%		———————————————%————————————————
Direct cut (DC):
Without	27.4¹	5.5	0.04	0.67	1.74	0.09	0.87	0.41	0.02
With	24.5	5.0	0.03	0.26	3.45	0.37	0.82	0.72	0.04
Wilted (WT):
Without	39.8	7.5	0.01	0.10	0.45	0.01	0.24	0.01	<0.01
With	35.1	7.5	0.01	<0.01	0.17	0.01	0.59	0.03	<0.01
Significance (P):
Treatment	<0.01	<0.01	0.02	0.29	<0.01	<0.01	0.01	<0.01	<0.01
MSD²	3.1	1.2	0.01	0.19	0.80	0.07	0.59	0.24	0.01

1 Each value is the mean of four samples.

2 MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 7.2. Dry matter (DM) intake (DMI) and digestibility of DM and fiber frac- tions of gamagrass preserved as baleage without and with an inoculant (DM basis).
Treatment	DMI	Digestibility¹
	DMI	DM	NDF	ADF	HEMI	CELL
	lb/100 lb²	————————%—————————
Direct cut (DC):
Without	1.96³	49.2	53.9	61.2	42.0	63.6
With	2.05	54.3	55.2	60.5	47.5	65.7
Wilted (WT):
Without	2.16	54.4	59.3	62.4	55.2	65.6
With	2.13	56.0	59.9	62.1	57.0	66.9
Significance (P):
Treatment	0.84	0.08	0.07	0.81	<0.01	0.40
MSD⁴	0.70	5.9	5.8	6.3	6.0	0.50

¹ NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellu- lose; CELL = cellulose.

² Body weight basis.

³Each value is the mean of four steers.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100)

t-test and can be used to compare any two treatments.

Table 7.3. In vitro dry matter disappearance (IVDMD) and nutritive value¹ of as-fed (AF) gamagrass preserved as baleage without and with an inoculant (dry matter basis).
Treatment	IVDMD		CP		NDF		Fiber Fractions
	AF	DV²	AF	DV	AF	DV	ADF	HEMI	CELL	Lignin
	—————————————————%——————————————————
Direct cut (DC):
Without	57.8³	-1.2	9.4	-0.7	75.3	2.7	45.7	29.6	36.8	6.6
With	63.3	0.1	12.0	-0.2	68.9	0.5	40.3	28.5	35.3	5.4
Wilted (WT):
Without	60.7	-2.6	9.0	-1.4	77.9	3.3	44.3	33.6	37.2	6.4
With	59.1	-3.1	9.1	-1.1	76.4	3.1	43.5	32.9	37.1	6.4
Significance (P):
Treatment	<0.01	0.28	<0.01	0.15	<0.01	0.21	<0.01	<0.01	0.02	<0.01
MSD⁴	1.7	4.4	0.9	1.3	1.9	3.4	0.9	1.0	1.3	0.4

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² DV = difference value (weighback concentration minus AF concentration).

³ Each value is the mean of four samples.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Experiment 8. Gamagrass Preserved as Hay and Silage and Compared with Silages of a Temperate and Tropical Corn: Nutritive Value

Traditionally, corn silage has been the major forage preserved as silage in most ruminant production systems. The competition for corn grain as a human food source and for biofuel purposes, however, will likely limit the future of corn grain as an animal feed. Our objective in this experiment was to assess and compare the quality of a perennial native grass, in this case two cultivars of gamagrass (preserved as hay and as silage), and a temperate and a tropical corn (preserved as silage).

Materials and Methods

A well-established field of Iuka and Pete gamagrass provided the gamagrass hays and silages used in this experiment. Both fields were burned in mid-February to remove all fall carryover growth and topdressed in early March with 80 pounds per acre of nitrogen in preparation for growth of the experimental forages. All treatments of gamagrass were cut in the late-vegetative stage. Forage preserved as silage was cut with a mower-conditioner set to a 4-inch stubble and immediately chopped with a conventional forage chopper, blown into a self-unloading wagon, and conveyed into an upright experimental silo according to normal procedures (Appendices GP-1 and GP-2). Forage preserved as hay was cut with a flail chopper set to a 4-inch stubble and blown directly into a self-unloading wagon. The forage was transported to a bulk-barn dryer located at the NC State University Forage-Animal Metabolism Unit, Raleigh, NC. The forage was dried overnight (inlet set at 180°F). After drying, the forage was baled directly out of the dryer using a conventional square baler. The baled hay was then stored on wooden pallets in an experimental hay barn until processed for feeding (Appendix GP-1).

The corn for silage consisted of the temperate cultivar Pioneer 3156 and the tropical cultivar Dekalb 678C. Plantings were made in April using conventional procedures, harvested at the early-dent stage, and ensiled (Appendix GP-2). The following six treatments were then available for forage quality evaluation:

Gamagrass:

Iuka hay: cut, dried, baled
Iuka silage: cut, chopped, and ensiled
Pete hay: cut, dried, baled
Pete silage: cut, chopped, and ensiled

Corn:

Temperate corn silage: harvested at early dent, ensiled
Tropical corn silage: harvested at early dent, ensiled

Four experiments were conducted consisting of two intake and digestibility experiments (Experiment 8A and Experiment 8C) and an associated mastication experiment (Experiment 8B and Experiment 8D). In Experiments 8A and 8B, we compared the two gamagrass cultivars when preserved as hay or as silage. In the other two experiments (8C and 8D), we compared the silages of gamagrass and corn.

Intake and digestibility estimates were obtained using steers in a randomized complete block design with four steers (replicates) per treatment. An exception was in the silage experiment, in which silage of the tropical corn cultivar was limited and fed to three steers. In the experiments, the steers were grouped by fours and assigned at random to treatments within replicate (Experiment 8A: steer mean weight = 509 ± 37 pounds; Experiment 8C: steer mean weight = 483 ± 36 pounds). Steers were fed at 12.8% excess in the gamagrass experiment and at 13.0% excess in the silage experiment. All experiments were conducted according to normal procedures (Appendix GP-3). Also masticate characterization, including particle-size distribution of the dry matter, was carried out and conducted according to normal procedures (Appendices GP-4 and GP-5).

All as-fed hay, weighback, and masticate samples were analyzed for nutritive value, and fecal samples were analyzed for chemical composition, according to normal procedures (Appendix GP-6). The data were statistically analyzed according to the experimental design (Appendix GP-7).

Results and Discussion

At time of ensiling, the dry matter concentrations of the two gamagrass forages were lesser compared with those of the corn silages (Table 8.1). Iuka was greater in dry matter than Pete, whereas the two corn silages were similar. As expected, the corn silages fermented at greater levels than the gamagrass, having lesser pH (4.0 versus 4.5) and attributed to the greater starch presence found in corn grain. The pH of the gama- grass silage was below 5.0, with Iuka lesser than Pete (4.4 versus 4.7), but both preserved reasonably well. The major difference between corn and gamagrass silage was the greater concentration of lactic acid in corn (Table 8.1). In general, temperate corn fermented better than tropical corn and Iuka fermented better than Pete.

Experiment 8A (Gamagrass Hay versus Silage)

Steers consumed more gamagrass hay than silage and more of Iuka forage than of Pete (Table 8.2). This was consistent regardless of preservation method. Dry matter digestibility was not altered by either cultivar or method of preservation. However, digestible intakes of dry matter, neutral detergent fiber, and hemicellulose were greater for gamagrass when preserved as hay compared with preservation as silage. The greater digestible intakes of hay were attributed mainly to greater dry matter intake—except for hemicellulose, which had greater digestibility.

The as-fed forage differed between hay and silage with hay having greater in vitro true dry matter dis- appearance and concentrations of neutral detergent fiber, and hemicellulose (Table 8.3). However, Iuka hay and silage were similar to Pete hay and silage in in vitro true dry matter disappearance and most of the fiber concentrations, but neutral detergent fiber was greater and crude protein was less. These differences between gamagrass cultivars when preserved as hay or silage were not always consistent. This resulted in a cultivar by preservation method interaction for in vitro true dry matter disappearance, crude protein, and cellulose. The difference values (weigh-back concentration minus as-fed concentration) indicate that some degree of selective consumption occurred, with steers selecting hays over silages.

Table 8.1. Ensiling characteristics of gamagrass and corn when preserved in upright silos, Experiment A-D (dry matter basis).
Treatment	DM¹	pH	Alcohol		Fatty Acids
	DM¹		Ethanol	Methanol	Acetic	Propionic	Lactic	Butyric	Isobutyric
	%		———————————————% ———————————————
Gamagrass (GG):
Iuka (IK)	18.4²	4.4	0.16	0.62	2.6	0.47	4.3	0.66	0.05
Pete (PT)	16.7	4.7	0.35	0.08	3.3	0.75	1.5	1.24	0.08
Corn (CN):
Temperate (TM)	24.3	3.9	0.63	0.06	2.4	0.34	5.5	0.26	0.01
Tropical (TP)	24.0	4.1	0.11	0.05	1.8	0.01	4.6	0.01	0.03
Significance (P):
Treatment	<0.01	<0.01	0.06	0.21	<0.01	<0.01	<0.01	0.04	0.02
GG vs. CN	<0.01	<0.01	0.38	0.19	<0.01	<0.01	<0.01	0.01	0.01
IK vs. PT	0.05	0.01	0.31	0.16	0.01	0.07	<0.01	0.16	0.07
TM vs. TP	0.67	0.04	0.02	0.30	0.02	0.04	0.21	0.54	0.56
MSD³	1.5	0.2	0.42	0.04	0.4	0.30	1.4	0.91	0.05

¹DM = dry matter.

² Each value is the mean of four samples.

³MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 8.2. Dry matter (DM) intake (DMI), digestibility, digestible intakes of DM and associated nutritive value¹ of gamagrass preserved as hay and silage, Experiment 8A (DM basis).
Treatment	DMI	Digestibility					Digestible Intake
	DMI	DM	NDF	ADF	HEMI	CELL	DM	NDF	ADF	HEMI	CELL
	lb/100 lb²	————————%————————					———————lb/100 lb——————
Hay (H):
Iuka (IK)	2.25³	59.9	64.5	64.3	64.8	70.2	1.35	1.07	0.55	0.53	0.53
Pete (PT)	2.19	62.6	68.2	68.0	68.3	74.2	1.37	1.10	0.55	0.55	0.53
Silage (S):
Iuka (IK)	1.99	59.5	61.1	65.3	54.9	71.1	1.18	0.84	0.53	0.31	0.52
Pete (PT)	1.73	61.0	65.3	70.0	58.7	75.4	1.07	0.80	0.51	0.29	0.50
Significance (P):
Treatment	<0.01	0.87	0.28	0.27	0.03	0.27	0.07	0.01	0.77	<0.01	0.80
H vs. S	<0.01	0.73	0.22	0.48	0.01	0.61	0.01	<0.01	0.37	<0.01	0.43
IK vs. PT	0.04	0.48	0.13	0.07	0.25	0.07	0.56	0.89	0.79	0.98	0.67
Interaction	0.16	0.85	0.90	0.84	0.99	0.93	0.40	0.56	0.68	0.44	0.73
MSD⁴	0.21	11.6	8.9	7.8	9.6	7.5	0.27	0.17	0.12	0.07	0.11

¹ NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Body weight basis.

³ Each value is the mean of four steers.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 8.3 In vitro true dry matter disappearance (IVTD) and nutritive value¹ of as-fed (AF) forage preserved as hay and silage, Experiment 8A (dry matter basis).
Treatment	IVTD		CP		NDF		Fiber Fractions
	AF	DV²	AF	DV	AF	DV	ADF	HEMI	CELL	Lignin
	—————————————————% —————————————————
Hay (H):
Iuka (IK)	70.8³	-6.1	11.0	-2.0	74.4	2.4	38.6	37.8	34.1	4.4
Pete (PT)	72.3	-6.7	11.8	-2.2	73.8	2.0	37.6	36.2	32.9	4.3
Silage (S):
Iuka (IK)	67.3	-1.7	11.4	-0.6	69.3	0.5	41.2	28.1	36.8	4.6
Pete (PT)	66.9	-2.1	11.4	-1.4	71.0	2.9	42.4	28.5	38.1	4.3
Significance (P):
Treatment	<0.01	<0.01	0.01	0.03	<0.01	0.08	<0.01	<0.01	<0.01	0.01
H vs. S	<0.01	<0.01	0.98	0.01	<0.01	0.41	<0.01	<0.01	<0.01	0.05
IK vs. PT	0.19	0.39	0.01	0.15	0.05	0.12	0.47	0.06	0.48	<0.01
Interaction	0.03	0.93	0.01	0.34	<0.01	0.04	<0.01	0.95	<0.01	0.10
MSD⁴	1.1	1.8	0.4	1.2	2.1	0.7	0.5	0.6	0.2	0.2

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² DV = difference value (weighback concentration minus AF concentration).

³ Each value is the mean of four samples.

⁴MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 8.4. Chemical composition¹ of feces from steers fed gamagrass preserved as hay and silage, Experiment 8A (dry matter basis).
Treatment	CP	NDF	Fiber Fractions
	CP	NDF	ADF	HEMI	CELL	Lignin
	——————————% —————————
Hay (H):
Iuka (IK)	11.1²	65.5	34.1	31.5	24.8	8.5
Pete (PT)	12.0	63.7	32.8	30.9	23.2	8.3
Silage (S):
Iuka (IK)	10.5	66.8	35.3	31.5	26.3	8.5
Pete (PT)	11.6	65.2	33.7	31.5	24.4	8.6
Significance (P):
Treatment	0.04	<0.01	<0.01	0.26	<0.01	0.93
H vs. S	0.17	<0.01	<0.01	0.21	<0.01	0.65
IK vs. PT	0.01	<0.01	<0.01	0.27	<0.01	0.98
Interaction	0.81	0.63	0.53	0.24	0.72	0.65
MSD³	1.1	1.0	0.8	0.9	1.1	0.9

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid deter- gent fiber; HEMI = hemicellulose; CELL = cellulose.

² Each value is the mean of four steers.

³MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

These differences are consistent with the subsequent fecal composition analysis. Feces from the hay treatments had lesser concentrations of neutral detergent fiber and the constituent fiber fractions of acid detergent fiber and cellulose (Table 8.4). Further, feces composition of the two gamagrass cultivars differed, with Iuka lesser in crude protein and neutral detergent fiber and its fiber constituents of acid detergent fiber and cellulose. It is worthy of note though, that all differences were rather minimal and probably of little biological importance as indicated by the forages’ generally similar digestibilities (Table 8.2).

Experiment 8B (Gamagrass Hay versus Silage)

Examination of the whole masticate indicates that steers incorporated appreciable saliva into the hay treatments, which averaged only 18.6% dry matter—but still greater than the silage dry matter average (Table 8.5). The median particle size of the masticate dry matter was greater for the hays compared with the silages, and the masticate in vitro true dry matter disappearance and crude protein were greater in hays than in silages. However, the neutral detergent fiber concentration in hays was lesser than in silages. Generally, masticates of Iuka and Pete silage and hay were similar in median particle size, in vitro true dry matter disappearance, and crude protein, but Pete masticates had greater differences between hay and silage in the concentrations of neutral detergent fiber and crude protein (significant interaction) than Iuka masticates.

Gamagrass hay had a greater proportion of large particles (46.1%) than silage (39.7%), with greater in vitro true dry matter disappearance and crude protein but lesser neutral detergent fiber. Generally, Iuka and Pete forages were similar across preservation methods, although some interactions were evident (Table 8.5). The proportions of medium particles were not altered by preservation method (mean = 46.3%), but hay was greater in nutritive value than silage. Small particles constituted a lesser proportion of masticate dry matter in hay (11.3%) than in silage (12.3%), and the hay particles were again greater in nutritive value. Further, the small particles in Iuka masticate were greater in nutritive value than those of Pete.

Experiment 8C (Gamagrass Silage versus Corn Silage)

Steers consumed both gamagrass silages and corn silages similarly, but consumed greater Iuka silage than Pete silage (Table 8.6). Steers digested the dry matter of all silages similarly, but digested neutral detergent fiber, acid detergent fiber, and cellulose greater for gamagrasses than for the corn cultivars. Also, the acid detergent fiber and cellulose of the temperate corn was more digestible than that of the tropical corn. Digestible intakes of neutral detergent fiber and its constituent fiber fractions were greater for the gamagrass than the corn and attributed to the greater dry matter intake noted for Iuka (Table 8.6).

Table 8.5. Masticate dry matter (DM), median particle size (MPS), and particle-size classes¹ and associated nutritive value² of gamagrass preserved as hay and silage, Experiment 8B (DM basis).
Treatment	Whole Masticate					Particle-size Classes
	DM	MPS	IVTD	CP	NDF	Large				Medium				Small
	DM	MPS	IVTD	CP	NDF	Prop³	IVTD	CP	NDF	Prop	IVTD	CP	NDF	Prop	IVTD	CP	NDF
	%	mm	———————————————————————— %————————————————————————
Hay (H):⁴
Iuka (IK)	19.5	1.6	75.6	10.9	66.9	45.9	73.2	9.2	70.1	45.2	77.1	12.1	65.1	8.9	80.4	14.1	58.9
Pete (PT)	17.7	1.6	76.6	12.1	67.3	46.3	74.7	10.3	70.4	44.4	78.5	13.6	65.3	9.3	77.1	14.0	61.4
Silage (S):⁵
Iuka (IK)	7.3	1.3	69.2	9.4	67.5	37.7	66.2	8.0	71.1	49.1	69.6	9.5	67.1	13.2	76.0	12.9	59.0
Pete (PT)	7.2	1.4	68.6	7.6	72.5	41.8	66.8	6.7	74.6	46.7	68.9	7.7	72.5	11.5	74.6	10.2	65.3
Significance (P):
Treatment	<0.01	0.08	<0.01	<0.01	<0.01	0.16	<0.01	<0.01	<0.01	0.04	<0.01	<0.01	<0.01	0.06	<0.01	<0.01	<0.01
H vs. S	<0.01	0.01	<0.01	<0.01	0.01	0.04	<0.01	<0.01	<0.01	0.13	<0.01	<0.01	<0.01	0.01	<0.01	<0.01	0.07
IK vs. PT	0.43	0.54	0.68	0.15	0.01	0.39	0.13	0.63	0.01	0.37	0.56	0.31	0.01	0.52	0.01	<0.01	<0.01
Interaction	0.52	0.52	0.21	<0.01	0.02	0.48	0.47	<0.01	0.03	0.65	0.08	<0.01	0.01	0.32	0.19	<0.01	0.06

¹ Large = > 1.7mm; medium = ≤1.7mm and >0.5mm; small < 0.5 mm.

² IVTD = in vitro true dry matter disappearance; CP = crude protein; NDF = neutral detergent fiber.

³ Prop = proportion of dry matter.

⁴ Each value is the mean of five steers.

⁵ Each value is the mean of four steers

The nutritive values of the as-fed silages indicate that the gamagrass, except for crude protein, was lesser in nutritive value than corn. Gamagrass silages had lesser in vitro true dry matter disappearance and greater concentrations of neutral detergent fiber and constituent fiber fractions than corn (Table 8.7). Further, Iuka gamagrass silage was generally greater in nutritive value (lesser neutral detergent fiber) than Pete silage, and temperate corn was greater in nutritive value (greater in vitro true dry matter disappearance and lesser neutral detergent fiber and fiber constituents) than tropical corn.

Feces composition generally reflects the greater digestibility of neutral detergent fiber and its constituents for gamagrass (Table 8.6). Feces from steers fed gamagrass silages had lesser concentrations of neutral detergent fiber and its constituents than did feces from steers fed the corn silages (Table 8.8). Further, the crude protein concentration in feces from steers fed gamagrass reflects the greater concentration in the as-fed forage (Table 8.7). Also, the greater nutritive value of temperate corn silage (Table 8.7) is reflected in the lesser concentrations of neutral detergent fiber and its constituent fiber fractions in the feces from steers fed temperate corn silage compared to that from steers fed tropical corn silage.

Experiment 8D (Gamagrass Silage versus Corn Silage)

The diets selected by steers, represented by the whole masticate, showed gamagrass and corn silage to differ (Table 8.9). Gamagrass was lesser in dry matter, reflecting incorporation of saliva, and had smaller median particle size in the consumed dry matter—which was lesser in nutritive value than corn silage. Generally, the masticate of Pete gamagrass was the least in crude protein and greatest in neutral detergent fiber. Also, temperate corn silage was greater in nutritive value than tropical corn silage and reflects the as-fed forage (Table 8.7)

Separating the masticate dry matter into particle-size classes showed gamagrass to have a lesser proportion of large particles (42.4%) than corn silage (60.3%), but a greater proportion of medium particles (46.3%) than corn silage (28.4%). Gamagrass and corn silages had similar proportions of small particles (mean = 11.3%). In general, the nutritive value of corn silage was greater than gamagrass across all particle-size classes. No differences were noted in nutritive value between Iuka and Pete gamagrass for the three particle-size classes. A noted exception occurred in the small particle-size class: Iuka silage had greater crude protein and lesser neutral detergent fiber than Pete silage. Comparing the corn silages, the temperate cultivar showed greater nutritive value in the large and small particle-size classes. The two corn silages, however, had no differences in nutritive value in the medium particle-size class (Table 8.9).

Table 8.6. Dry matter (DM) intake (DMI), digestibility, intake of digestible DM, and associated nutritive value¹ of gamagrass and corn preserved as silage, Experiment 8C (DM basis).
Treatment	DMI	Digestibility					Digestible Intake
	DMI	DM	NDF	ADF	HEMI	CELL	DM	NDF	ADF	HEMI	CELL
	lb/100 lb²	———————% ——————					————— lb/100 lb——————
Gamagrass (GG):
Iuka (IK)	1.99³	59.5	61.1	65.3	54.9	71.1	1.18	0.84	0.53	0.31	0.52
Pete (PT)	1.73	61.0	65.3	70.0	58.5	75.4	1.07	0.80	0.51	0.29	0.50
Corn (CN):
Temperate (TM)	1.66	64.7	55.5	58.9	50.7	63.7	1.07	0.49	0.30	0.19	0.28
Tropical (TP)	1.74	54.5⁴	46.4⁴	46.8⁴	45.9⁴	53.5⁴	0.91⁴	0.48⁴	0.28⁴	0.20⁴	0.27⁴
Significance (P):
Treatment	0.07	0.25	0.03	<0.01	0.20	<0.01	0.21	<0.01	<0.01	0.01	<0.01
GG vs. CN	0.07	0.85	0.01	<0.01	0.06	<0.01	0.12	<0.01	<0.01	<0.01	<0.01
IK vs. PT	0.05	0.72	0.37	0.30	0.50	0.29	0.60	0.57	0.62	0.53	0.57
TM vs. TP	0.49	0.06	0.11	0.03	0.41	0.04	0.19	0.81	0.56	0.81	0.72
MSD⁵	0.27	11.6	11.3	10.1	13.9	9.1	0.29	0.16	0.09	0.07	0.08

¹ NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Body weight basis.

³ Each value is the mean of four steers.

⁴ Each value is the mean of three steers.

⁵MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 8.7 In vitro true dry matter disappearance (IVTD) and nutritive value¹ of as-fed (AF) gamagrass and corn preserved as silage, Experiment 8C (dry matter basis).
Treatment	IVTD		CP		NDF		Fiber Fractions
	AF	DV²	AF	DV	AF	DV	ADF	HEMI	CELL	Lignin
	———————————————————% ———————————————————
Gamagrass (GG):
Iuka (IK)	67.3³	-1.7	11.4	-0.6	69.3	0.5	41.2	28.1	39.8	4.6
Pete (PT)	66.9	-2.1	11.4	-1.5	71.0	2.9	42.4	28.5	38.1	4.3
Corn (CN):
Temperate (TM)	75.0	0.2	8.6	-0.5	53.0	-4.6	30.6	22.4	26.7	3.1
Tropical (TP)	66.0	-2.7	9.1	-0.6	61.5	0.8	35.2	26.2	30.4	4.3
Significance (P):
Treatment	<0.01	0.13	<0.01	0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
GG vs. CN	0.01	0.43	<0.01	0.02	<0.01	0.01	<0.01	<0.01	<0.01	<0.01
IK vs. PT	0.67	0.69	0.88	<0.01	0.03	0.13	0.04	0.23	<0.01	0.06
TM vs. TP	<0.01	0.03	0.05	0.79	<0.01	0.01	<0.01	<0.01	<0.01	<0.01
MSD⁴	2.1	2.9	0.5	0.5	1.4	1.4	1.1	0.7	0.7	0.3

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² DV = difference value (weighback concentration minus AF concentration).

³ Each value is the mean of four samples.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 8.8. Chemical composition¹ of feces from steers fed gamagrass and corn silages, Experiment 8C (dry matter basis).
Treatment	CP	NDF	Fiber Fractions
	CP	NDF	ADF	HEMI	CELL	Lignin
	——————————% ——————————
Gamagrass (GG):
Iuka (IK)	10.5²	66.8	35.3	31.5	26.3	8.5
Pete (PT)	11.6	65.3	33.7	31.5	24.4	8.6
Corn (CN):
Temperate (TM)	10.5	68.9	37.0	31.9	28.4	7.2
Tropical (TP)	9.0³	72.1³	41.0³	31.1³	31.0³	9.2³
Significance (P):
Treatment	0.02	<0.01	<0.01	0.50	<0.01	0.01
GG vs. CN	0.01	<0.01	<0.01	0.95	<0.01	0.32
IK vs. PT	0.09	0.13	0.02	0.96	0.06	0.81
TM vs. TP	0.05	0.01	<0.01	0.15	0.03	<0.01
MSD⁴	1.5	2.1	1.2	1.4	2.0	1.0

¹ CP = crude protein; NDF = neutral detergent fiber; ADF = acid detergent fiber; HEMI = hemicellulose; CELL = cellulose.

² Each value is the mean of four steers.

³Each value is the mean of three steers.

⁴ MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

Table 8.9. Whole-masticate dry matter (DM), median particle size (MPS), particle-size classes, and associated nutritive value¹ of gamagrass and corn preserved as silage, Experiment 8D (DM basis).
Treatment	Whole Masticate					Particle-size classes²
	DM	MPS	IVTD	CP	NDF	Large				Medium				Small
	DM	MPS	IVTD	CP	NDF	Prop³	IVTD	CP	NDF	Prop	IVTD	CP	NDF	Prop	IVTD	CP	NDF
	%	mm	————————————————————— %——————————————————————
Gamagrass (GG): ⁴
Iuka (IK)	8.1	1.4	68.5	9.4	68.3	40.3	65.4	7.9	71.8	47.5	70.2	10.0	66.2	12.2	74.3	12.4	61.9
Pete (PT)	8.0	1.5	68.0	7.6	73.2	44.5	66.0	6.7	75.3	45.1	69.5	8.1	71.6	10.4	72.9	9.7	68.2
Corn (CN): ⁵
Temperate (TM)	11.4	2.1	75.6	8.1	53.5	57.4	73.5	7.5	57.2	29.2	75.0	8.2	54.6	13.4	85.3	10.6	34.8
Tropical (TP)	11.5	2.3	69.3	8.3	60.1	63.3	67.3	7.4	62.8	27.6	71.7	9.2	57.2	9.1	78.2	12.1	47.9
Significance (P):
Treatment	<0.01	0.03	<0.01	0.03	<0.01	0.01	<0.01	0.25	<0.01	<0.01	0.13	0.17	<0.01	0.12	<0.01	<0.01	<0.01
GG vs. CN	<0.01	0.01	<0.01	0.49	<0.01	<0.01	<0.01	0.73	<0.01	<0.01	0.07	0.61	<0.01	0.99	<0.01	0.48	<0.01
IK vs. PT	0.77	0.72	0.69	0.01	0.05	0.50	0.74	0.06	0.13	0.56	0.77	0.07	0.16	0.42	0.28	<0.01	0.02
TM vs. TP	0.87	0.47	<0.01	0.67	<0.01	0.24	<0.01	0.95	0.01	0.63	0.12	0.22	0.38	0.03	<0.01	0.01	<0.01
MSD⁶	1.2	0.6	2.4	1.1	4.1	11.9	3.1	1.4	4.1	7.6	5.5	2.1	0.71	4.7	2.2	1.1	4.2

¹ IVTD = in vitro true dry matter disappearance; CP = crude protein; NDF = neutral detergent fiber.

² Large = > 1.7mm; Medium = ≤1.7mm and >0.5mm; Small < 0.5 mm.

³ Prop = proportion of dry matter.

⁴ Each value is the mean of four steers.

⁵ Each value is the mean of six steers.

⁶MSD = minimum significant difference from the Waller-Duncan k-ratio (k = 100) t-test and can be used to compare any two treatments.

The distribution of the masticate dry matter among treatments is more readily viewed when presented in figure form by plotting the cumulative percentage of oversize particles across the various sieve sizes (Figure 8.1). The relationship between corn silages and between gamagrass silages and between gamagrass hays (evaluated in Experiment 8A) and among all six treatments is evident.

Summary and Conclusions

Both Iuka and Pete gamagrass fermented well with the pH below 5.0 (Iuka = 4.4 and Pete = 4.7).
Steers consumed Iuka hay and silage in greater amounts than Pete hay and silage.
The dry matter digestibility of Iuka and Pete forage was similar whether preserved as hay or silage.
Steers digested gamagrass silage similar to corn silage.
Both corn cultivars fermented well, with the pH of temperate corn silage averaging 3.9 and tropical corn silage averaging 4.2.
Generally, temperate corn silage had an advantage in nutritive value over tropical corn silage, but quality was similar.
All four cultivars evaluated in this experiment can make a contribution to ruminant production systems.

Line Graph of cumulative Percent Oversize vs. Sieve Size (mm)

Figure 8.1. Particle size distribution of masticate dry matter for Iuka and Pete gamagrass preserved as hay and silage, and for temperate corn silage (TM-CS) and tropical corn silage (TP-CS), Experiment 8D (n = 4 for gamagrass; n = 6 for corn silage).

Appendices: General Procedures of Experimentation

The general procedures (GP) followed in conducting the various experiments described in this bulletin are noted below and are not repeated elsewhere. Departure from any procedure or specific details related to any experiment are noted under the Materials and Methods section of each experiment with reference to the appropriate general procedures outlined below. Animal experiments were conducted primarily during October through April, but occasionally an experiment was extended into May. This practice avoided the potential negative influences of elevated temperatures on animal behavior during the hot summer months.

GP-1. Hay Handling

All hays evaluated in the various experiments were harvested from well-established stands. When hay was field cured, the forage was cut with a mower-conditioner and baled with a conventional square baler. When hay was artificially dried, the forage was cut with a flail-chopper, blown into a self-unloading wagon, and transported to a bulk drying barn at the NC State University Forage-Animal Metabolism Unit, Raleigh, NC. After drying, the hay was baled directly from the dryer with a conventional square baler. Prior to feeding, field-cured hay bales were passed through a hydraulic bale press (Van Dale 5000, J. Starr Industries, Fort Atkins, WI) with stationary knives spaced at 4 inches. This process reduced hay into 3- to 5-inch lengths with little to no leaf loss, aided feeding, and minimized the potential for the hay to be tossed out of the manger by the animals. Flail-chopped forage was reduced into 3- to 6-inch lengths when cut and required no further processing prior to feeding.

GP-2. Ensiling and Handling

In preparation for ensiling, the switchgrass and gamagrass were first swathed with a mower conditioner set to leave a 4- to 5-inch stubble. For the direct-cut silage treatments, the windrow was chopped immediately with a conventional field chopper with a pickup attachment, chopped into 0.25- to 0.5-inch lengths, and blown into a self-unloading wagon. For the wilted treatment, the windrow was tedded for wilting, then windrowed and chopped as noted above. In the case of baleage, the windrow was baled using a large round bale. The direct-cut and wilted forage and the bales for baleage were transported to the Forage-Animal Metabolism Unit, Raleigh, NC, for ensiling. The forage for silage was placed in upright experimental silos previously fitted with plastic liners, packed by treading, and sealed off at the top. Forage ensiled in sausage-bag silos was mechanically blown into each bag and sealed off at completion. The round bales for baleage were each wrapped with four layers of 0.025 mm white plastic and placed outside adjacent to the Metabolism Unit.

In all cases (silage and baleage) the forage was left undisturbed for at least 60 days to permit fermentation. Upon opening, any surface mold was removed and the silage used as appropriate for the experiment. In the case of baleage, the plastic was removed and the bale placed into a single-bale, multiblade, power-take-off-driven tub-grinder, where the forage was reduced into 2- to 6-inch lengths in preparation for feeding.

GP-3. Dry Matter Intake and Whole-tract Digestibility

We evaluated forages by feeding them to steers at the NC State University Forage-Animal Metabolism Unit in an animal facility consisting of a metal structure partitioned into three areas. On one end was a feed preparation area. The middle was an enclosed, but well-ventilated, central area equipped with digestion crates and temperature control designed to keep the ambient air between 50°F and 85°F. The third area, on the opposite end from the feed preparation area, was equipped with a raised, basket weave, metal platform fitted with electronic gates (American Calan Inc., Northwood, NH) to control animal access to mangers for individual intake measurements. The intake area was beneath an extension of the roof with three open sides. In the intake phase, each animal wore an electronically keyed collar to allow access to only one manger, but each had free access to trace mineralized salt and water and could lounge with other animals. Prior to each experiment, animals were conditioned to the electronic gates before random assignment to the appropriate forage treatment.

Intake Phase

The intake phase of an experiment normally consists of a 21-day period with the first 7 days used to adjust the animal to its feed. This intake phase was increased to 28 days when feeding silages, allowing the first 14 days for adjustment to potential differences in fermentation characteristics and the last 14 days to estimate daily dry matter intake (Burns et al., 1994). A recorded weight of forage was fed twice daily, allowing about 13 to 15% excess. A daily sample of the fed forage (as-fed) was obtained for each animal and composites made on a weekly basis. The unconsumed forage (weighback) was weighed twice daily, saved separately for each animal-treatment combination, and composited for each week.

Digestibility Phase

The digestibility phase consisted of 12 days when immediately following an intake period or 19 days during a separate digestibility evaluation. In either case, animals were moved into digestion crates. The digestibility phase consisted of a 7-day adjustment period for hay or a 14-day adjustment period for silage, followed by a 5-day total fecal and urine (if applicable) collection (Cochran and Galyean, 1994). A recorded weight of forage was fed twice daily at about 15% excess. A daily sample of the fed forage was obtained and weighback saved separately for each animal-treatment combination and composited for the 5-day collection period.

Feces were collected on a plastic sheet placed on the floor immediately in back of each digestion crate. Feces were removed periodically throughout the day and the daily total weight of feces recorded for each of five consecutive days. Feces were thoroughly mixed daily, and 5% of the fresh weight was placed in a freezer (5°F). When part of the experimental objectives, a second sample was obtained and placed in a freezer for freeze drying and particle size determination.

Samples

The weekly forage samples from the 14-day intake phase, the 5-day composite forage and fecal samples from the digestibility phase, and the associated weighback samples from the intake and digestibility phases were dried (generally hay was oven-dried at 131°F and silages frozen and freeze dried ) and weighed for dry matter determination. Dried samples for analysis were then thoroughly mixed and a 300 to 500g subsample ground in a Wiley Mill to pass a 1-mm screen and stored at room temperature until analyzed. The samples for feces particle-size determination remained in the freezer (5°F) until freeze dried and were dry sieved as noted below in procedure GP-4 for masticates.

In experiments using a randomized complete block design, the digestibility phase followed the intake phase and completed the experiment for each animal. However, in Latin square-designs, once animals completed one period, they returned to the intake facility following the digestibility phase to begin the next period.

GP-4. Masticate Collection and Processing

Mature, esophageally-fistulated, grade British-bred steers (800 to 1,400 pounds) were generally used and fed a standard forage about five days before initiation of an experiment. After adjustment to treatments (offered the previous afternoon), collections generally occurred at about 9:00 a.m. and 3:00 a.m. on two consecutive days. Animals were offered about 3 pounds of forage at each collection. The esophageal cannulas were removed and boluses collected by hand to ensure complete collection. The first five to six boluses were discarded, and the following 10 to 15 were collected. If chewing behavior was determined, the chews per bolus were recorded and each bolus was handled separately. We obtained a fresh- and freeze-dried weight of each bolus prior to mixing. Otherwise the boluses were placed on a large plastic tray, gently mixed, placed into two plastic bags, and immediately quick-frozen in liquid nitrogen (-319°F). The boluses were stored in a freezer (5°F) until freeze dried and then returned to the freezer until analyzed. The dried boluses were sampled for chemical analyses and for particle size determination.

GP-5. Particle Size Determination

Particle size estimates of the boluses were obtained by passing two subsamples of 15 grams each through a Fritsch Vibrator system (Fritsch Analysette, the Tekmor Co., Cincinnati, OH). Nine particle sizes were weighed consisting of dry matter retained on 5.60-, 4.00-, 2.80-, 1.70-, 1.00-, 0.50-, 0.25-, and 0.125-mm sieves and that which passed through the 0.125-mm sieve (<0.125 mm). The dry weight was recorded for the material retained on each sieve and that which passed through the 0.125-mm sieve. The percentages of cumulative particle weight oversize were determined and used to calculate median particle size (Fisher et al., 1988). Samples were composited across days and feeding times for each sieve size. Particle size estimates of feces were determined by passing one subsample through the Fritsch Vibrator system and the eight sieve sizes noted for masticate to obtain nine particle sizes. Sieved samples of both masticate and feces were stored either separately by individual sieve size or composites were made to form three particle-size classes of large (≥1.7 mm), medium (<1.7 and ≥0.50 mm), and small (<0.50 mm) prior to chemical analyses. The composite samples were ground in a cyclone mill (Udy Corp., Fort Collins, CO) to pass a 1-mm screen and stored in a freezer until analyzed.

GP-6. Laboratory Analysis

Nutritive value for all as-fed, weighback, and masticate samples, and chemical composition of fecal samples, as appropriate for the various experiments, were either analyzed fresh or after drying by wet chemistry and reported. Or these samples were used to develop calibration equations in association with the prediction of nutritive value using near-infrared reflectance spectroscopy (NIRS).

Fermentation characteristics of the baleages and silages were determined on preserved (frozen) samples according to Burns and Fisher (2012). In vitro dry matter disappearance was determined using a modification of the method by Tilley and Terry (1963), and in vitro true dry matter disappearance was determined by 48-hour fermentation in a batch fermentation vessel (Ankom Technology Corp., Fairport, NY) with artificial saliva and rumen inoculum according to Burns and Cope (1974). In vitro true fermentation was terminated with neutral detergent solution in an Ankom 200 fiber analyzer (Ankom Technology Corp., Fairport, NY) to remove the residual microbial dry matter. Ruminal inoculum was obtained from a mature rumen fistulated steer generally fed a mixed alfalfa (Medicago sativa L.) and orchardgrass (Dactylis glomerata L.) hay. Total nitrogen was determined colorimetrically (AOAC, 1990) with a Technicon Autoanalyzer (Bran and Luebbe, Buffalo, IL), and crude protein was estimated as 6.25 times the nitrogen concentration. Fiber fractions, consisting of neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, and ash were estimated using reagents according to Van Soest and Robertson (1980). Hemicellulose was determined by the difference between NDF and ADF (NDF minus ADF), as was cellulose, depending on procedures used.

GP-7. Statistical Analysis

The data from the intake, digestibility, and masticate phases for each experiment were analyzed and presented as least square means from the application of mixed-model methodology as appropriate based on the design for the particular experiment. Particle sizes, when determined, were expressed as percentages of cumulative particle weight oversize (sum of dry matter weight on each sieve versus weight from all larger sieves) and were used to determine mean and median particle size (Fisher et al., 1988). Means for all variables found significant in each experiment were compared by either trend analysis with a set of polynomial orthogonal contrasts or by a set of meaningful comparisons using orthogonal contrasts, as appropriate, within the mixed-model analysis of variance. A minimum significant difference was frequently included to assist the reader in determining differences between individual treatments.

References and Recent Related Publications

References

Association of Official Analytical Chemists (AOAC). 1990. Official Methods of Analysis. 15th ed. AOAC, Arlington, VA.

Burns, J.C., and W.A. Cope. 1974. Nutritive value of crownvetch forage as influenced by structural constituents and phenolic and tannin compounds. Agron. J. 66:195-200.

Burns, J.C., and D.S. Fisher. 2012. Intake and digestibility of big bluestem hay and baleage. Crop Sci. 52:2413-2420.

Burns, J.C., K.R. Pond, and D.S. Fisher. 1994. Measurements of intake. p. 494-532. In G.C. Fahey, Jr. et al. (ed.), Forage quality, evaluation, and utilization. ASA, CSSA, and SSSA, Madison, WI.

Cochran, R.C., and M.L. Galyean. 1994. Measurements of in vivo forage digestion by ruminants. p. 613-643. In G.C. Fahey, Jr. et al. (ed.), Forage quality, evaluation, and utilization. ASA, CSSA, and SSSA, Madison, WI.

Fisher, D.S., J.C. Burns, and K.R. Pond. 1988. Estimation of mean and median particle size of ruminant diets. J. Dairy Sci. 71:518-524.

Tilley, J., and R.A. Terry. 1963. A two-stage technique for in vitro digestion of forage crops. J. Br. Grassl. Soc. 18:104-111.

Van Soest, P.J., and J.B. Robertson. 1980. Systems of analysis for evaluating fibrous feeds. p. 49-60. In W.J. Pigden et al. (ed.), Standardization of analytical methodology for feeds. International Development Res. Center, Ottowa, Canada.

Recent Related Publications

Burns, J.C., et al. 1998. Carostan Flaccidgrass: Establishment, adaptation, production, management, forage quality, and utilization. Technical Bulletin 313. North Carolina Agricultural Research Service, North Carolina State University, Raleigh, NC.

Burns, J.C. et al. 2009. Switchgrass: Establishment, management, yield, nutritive value, and utilization. Technical Bulletin 326. North Carolina Agricultural Research Service, North Carolina State University, Raleigh, NC.

Burns, J.C. 2011. Advancement in assessment and the reassessment of the nutritive value of forages. Crop Sci. 51: 390-402.

Burns, J.C. 2011. Intake and digestibility among Caucasian bluestem, big bluestem, and switchgrass compared with bermudagrass. Crop Sci. 51: 2262-2275.

Burns, J.C., and Fisher, D.S. 2013. Steer performance and pasture productivity among five perennial warm-season grasses. Agron. J. 105: 113-123.

Burns, J.C., and Fisher, D.S. 2013. Steer intake, digestion, and ingestive behavior of switchgrass and alfalfa hays. Crop Sci. 53:716-723.

Burns, J.C., and Fisher, D.S. 2013. Steer responses to increasing proportions of legume when fed switchgrass hay. The Professional Animal Scientist 29:383-394.

Burns, J.C., E.B. Godshalk, and D.H. Timothy. 2008. Registration of ‘BoMaster’ switchgrass. Journal Plant Registrations 2:31-32.

Burns, J.C., E.B. Godshalk, and D.H. Timothy. 2008. Registration of ‘Performer’ switchgrass. Journal Plant Registrations 2:29-30.

Burns, J.C., and D. S. Fisher. 2010. Eastern gamagrass management for pasture in the mid-Atlantic region: I. Animal performance and pasture productivity. Agron. J. 102: 171-178.

Burns, J.C., and D. S. Fisher. 2010. Eastern gamagrass management for pasture in the mid-Atlantic region: II. Diet and canopy characteristics, and stand persistence. Agron. J. 102: 179-186.

Burns, J.C., Fisher, D.S., and Pond, K.R. 2011. Steer performance, intake, and digesta kinetics of switchgrass at three forage masses. Agron. J. 103: 337-350.

Burns, J.C., E.B. Godshalk, and D.H. Timothy. 2010. Registration of ‘Colony’ lowland switchgrass. J. Plant Reg. 4:189-194.

Burns, J.C., K.R. Pond, D.S. Fisher, and J.M. Luginbuhl. 1997. Changes in forage quality, ingestive mastication, and digesta kinetics resulting from switchgrass maturity. J. Anim. Sci. 75:1368-1379.

Eun, J.S., V. Fellner, J.C. Burns and M.L. Gumpertz. 2003. Eastern gamagrass evaluated as hay or silage for lactating dairy cows. The Professional Animal Scientist 19:362-369.

Eun, J. S., V. Fellner, J.C. Burns and M.L. Gumpertz. 2004. Fermentation of eastern gamagrass (Tripsacum dactyloides [L.] L.) by mixed cultures of ruminal microorganisms with or without supplemental corn. J. Anim. Sci. 82:170-178.

Fisher, D.S., J.C. Burns, and H.F. Mayland. 2005. Variation in ruminant preference for switchgrass hays cut at either sundown or sunup. Crop Sci. 45:1394-1402.

Huntington, G.B., and J.C. Burns. 2007. Afternoon harvest increases readily fermentable carbohydrate concentration and voluntary intake of gamagrass and switchgrass baleage by steers. J. Anim. Sci. 85: 276-284.

Huntington, G.B., and J.C. Burns. 2008. The interaction of harvest time of day of switchgrass hay and ruminal degradability of supplemental protein fed to beef steers. J. Anim. Sci. 86:159-166

Huntington, G.B., K. Magee, A. Matthews, M. Poore, and J. Burns. 2009. Urea metabolism in beef steers fed tall fescue, orchardgrass, or gamagrass hay. J. Anim. Sci. 87:1346-1353.

Magee, K.J., M.H. Poore, J.C. Burns, and G.B. Huntington. 2005. Nitrogen metabolism in beef steers fed gamagrass or orchardgrass hay with or without a supplement. Canadian J. Anim. Sci. 85: 107-109.

Sanderson, M.A., and J.C. Burns. 2010. Digestibility and intake of hays from upland switchgrass cultivars. Crop Sci. 50:2641-2648.

Stevens, D.R., J.C. Burns, D.S. Fisher, J.H. Eisemann. 2004. The influence of high nitrogen forages on the voluntary feed intake of sheep. J. of Anim. Sci. 82:1536-1542.

Sauve, A.K., G.B. Huntington, and J.C. Burns. 2009. The effects of total nonstructural carbohydrates and nitrogen balance on voluntary intake of goats and digestibility of gamagrass hay harvested at sunrise and sunset. Anim. Feed Sci. Tech. 148:93-106

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Silages of Native Switchgrass and Gamagrass: Fermentation Characteristics, Nutritive Value, and Quality

Contents

Abstract

Introduction

Section I. Switchgrass

Experiment 1. Initial Growth Switchgrass Cut in the Vegetative Stage: Ensiling Characteristics, Nutritive Value, and Quality

Material and Methods

Results and Discussion

Summary and Conclusions

Experiment 2. Switchgrass Cut in the Late-Boot Stage: Ensiling Characteristics, Nutritive Value, and Quality

Material and Methods

Results and Discussion

Experiment 2A

Experiment 2B

Summary and Conclusions

Experiment 3. Initial Growth Switchgrass Cut in the Headed Stage: Ensiling Characteristics, Nutritive Value, and Quality

Materials and Methods

Results and Discussion

Experiment 3A

Experiment 3B

Summary and Conclusions

Experiment 4. Regrowth Switchgrass Cut in the Heading Stage: Ensiling Characteristics, Nutritive Value, and Quality

Materials and Methods

Results and Discussion

Experiment 4A

Experiment 4B

Summary and Conclusions

Section II. Gamagrass

Experiment 5. Gamagrass Preserved as Hay, Baleage, and Silage: Ensiling Characteristics, Nutritive Value, and Quality

Materials and Methods

Results and Discussion

Experiment 5A

Experiment 5B

Summary and Conclusions

Experiment 6. Gamagrass Preserved as Direct-Cut Baleage, Wilted Baleage, Silage, and Hay: Ensiling Characteristics, Nutritive Va

Materials and Methods

Experiment 6A (Initial growth)

Experiment 6B (Regrowth)

Results and Discussion

Experiment 6A

Experiment 6B

Summary and Conclusions

Experiment 7. Potential Benefits from Inoculating Gamagrass Forage Prior to its Preservation as Baleage

Materials and Methods

Results and Discussion

Summary and Conclusions

Experiment 8. Gamagrass Preserved as Hay and Silage and Compared with Silages of a Temperate and Tropical Corn: Nutritive Value

Materials and Methods

Gamagrass:

Corn:

Results and Discussion

Experiment 8A (Gamagrass Hay versus Silage)

Experiment 8B (Gamagrass Hay versus Silage)

Experiment 8C (Gamagrass Silage versus Corn Silage)

Experiment 8D (Gamagrass Silage versus Corn Silage)

Summary and Conclusions

Appendices: General Procedures of Experimentation

GP-1. Hay Handling

GP-2. Ensiling and Handling

GP-3. Dry Matter Intake and Whole-tract Digestibility

Intake Phase

Digestibility Phase

Samples

GP-4. Masticate Collection and Processing

GP-5. Particle Size Determination

GP-6. Laboratory Analysis

GP-7. Statistical Analysis

References and Recent Related Publications

References

Recent Related Publications

Authors

Related Publications