Grazing management is an important tool for efficient utilization of the pasture as a resource and overall landscape management. To manage effectively, the land and livestock manager must keep plant and animal requirements in mind and maintain balance between them. One of the goals of effective grazing management is to match the nutritional requirements of the animals with the ability of the pasture to meet these needs.

Critical choices to be made in designing a grazing management program include which forages to graze, which animals will do the grazing, the stocking rate or height of grazing (how close, when to stop) and rotational or continuous stocking (how often, when to start). This discussion will assume rotational stocking as the selected stocking method. The main decisions that the grazier must make when using rotational stocking are the length of the rest period between grazing events and the length of time that the livestock will be on one paddock (the grazing period).

Determining the canopy height at which grazing should be discontinued in a particular paddock is the decision that has the greatest impact on pasture and animal productivity. Some graziers use pasture height as the indicator of when it is time to move cattle from a pasture or provide supplement to the animals. Others have a concept of how many animals they can carry on their pasture over a growing season (stocking rate). This concerns the prevention of weed infestation and the maintenance of good ground cover to ensure persistence of the desired forage species. The key is to control defoliation height so that the plant buds, from which growth takes place, are not damaged or completely removed by the grazing animal or by the clipping equipment. Appropriate “stop grazing or clipping” heights are based on enough leaf area and reserve energy in storage organs (including roots, lower stems, stolons, and rhizomes to allow good regrowth (see Table 1).

Heights to start grazing are related to balancing forage quantity and its nutritive value. Estimates of nutritive value include crude protein and digestibility. In general, the longer the regrowth period, the greater the accumulation of forage (taller and more mature plants) and the lower the nutritive value. A general guideline is that pastures should be grazed about a week before the grass heads out (goes to seed) or when the legume is in the early or mid-bud stage. The canopy heights indicated in Table 1 are an attempt to balance nutritive value and quantity of forage, and to ensure that plants have recovered sufficiently from a previous grazing event.

Herbage accumulates based on weather conditions (including rainfall and temperature), soil conditions (including moisture and availability of nutrients), and the intensity of defoliation (canopy height and residual leaf area). Therefore, the length of the required rest period to achieve a target grazing height to start grazing for each forage species is closely related to its seasonal growth pattern in North Carolina (see AG-789, Forages for North Carolina: General Guidelines and Concepts). In addition, erratic weather events within active months of growth can result in faster or slower plant regrowth; consequently, rest periods will need to be adjusted.

In general:

• Legumes such as alfalfa, birdsfoot trefoil, and red clover need rest periods of about three to four weeks throughout the season.
• Cool-season grasses such as tall fescue, orchardgrass, Kentucky bluegrass and ryegrass need as little as two weeks in cool weather and five to seven weeks during hot weather.
• Warm-season grasses such as bermudagrass, bluestem and sorghum sudangrass need five to six weeks during cool weather and about three weeks during hot weather.

One of the goals of an effective grazing program is to ensure a balance between the forage in the landscape and the demand by the grazing livestock. During periods of fast pasture growth, and if forage is in excess supply, the rest period should be shortened to avoid having stemmy, low-quality forage on the pasture. This can be accomplished by removing some paddocks from the rotation and using them for hay or haylage, or by increasing the stocking rate so that the grazing period can be reduced. Conversely, when forage is in limited supply due to plants being under stress (adverse environmental conditions for growth), the grazier may choose to end grazing and purchase hay if they feel that further grazing may seriously weaken the pasture. Other options include reducing the stocking rate, or, if possible, adding (or renting) new areas for grazing. If the stocking rate remains constant year-round, then graziers know that there could be periods of under- or over-grazing depending on the weather. Defining an optimal stocking rate (or grazing intensity) should be the primary focus of the land and livestock manager.