What is genomic testing?
The production of beef cattle in North Carolina is based primarily on cow-calf grazing systems. In recent years, there have been advances in all facets of the cow-calf production system from the increased adoption of defined breeding seasons to nutritional strategies that are tailored to wean heavier calves. These technologies have become more common as the demands of the marketplace have increased. Buyers are now emphasizing the genetic sources of their cowherds and are seeking bulls with documented genomic testing. The main benefits of genomic testing are parent verification and the calculation of genomic-enhanced expected progeny differences (GE-EPDs), which reflect an animal’s genetic value. In addition, genomic companies and breed associations offer other tests (add-ons) that cover breed-related genetic defects and screen for other tests such as persistently infected bovine viral diarrhea virus (PI-BVDV).
Parent verification is used to identify a calf’s parents (dam and sire). The main goal is establishing an accurate pedigree. This allows cattlemen to provide reliable information that can be beneficial for seedstock and commercial operations. Genetic verification is particularly useful in situations that involve multi-sire breeding pastures, artificial insemination (AI) or embryo transfer followed by clean-up bulls (natural mating), calves that may have been switched at birth, and ambiguous data records. Mistakes can happen such as pulling the wrong straw of semen during an artificial insemination. Parent verification offers the opportunity to resolve any confusion.
Each calf receives one copy ("allele") of the potential gene marker from each parent. For example (see Figure 1), when a bull that carries the alleles “AA” is crossed with a dam with the alleles “BB,” the calf must have the alleles “AB” because the calf receives a gene copy from each parent. If the testing of the calf found either AA or BB, the calf is not compatible, and the parentage is excluded. This is done by selecting and testing compatibility based on several unique single nucleotide polymorphism (SNPs or DNA markers).
How does genomic testing work?
Genomic companies and breed associations offer genetic tests for commercial cattle that many commercial producers are using to understand the genetic makeup of their herds. This information can be valuable when selecting replacement heifers (maternal traits) and for marketing steers (growth and carcass traits). The sampling process is similar for seedstock or commercial operations. Seedstock producers should contact their breed association for guidance about genomic testing.
Samples from the calf and its potential parents must be collected and submitted for genetic comparison. Fortunately, genetic material remains on file at the testing laboratories so that each animal’s results only have to be submitted one time. All AI sires will have genetic material on file and many seedstock suppliers will have tested their bulls. This makes testing the progeny of their bulls much easier. The same will be true for cows and herd bulls after their initial submission so genetic material from the calf in question may be the only sample to be submitted.
A blood sample is perhaps the lowest cost, most widely used type of genetic sample. Other tissues from tail hair, semen, and ear notches can also be used. Many producers like the convenience of tissue sampling units (TSU), which can collect clean, uncontaminated samples in seconds with minimal animal restraints. More information is available from breed associations.
The actual analysis and comparison of the samples are generally handled through the breed association associated with the animals in question (see Table 1). Care should be taken when collecting samples because breed associations and genomic companies will reject samples that do not meet their criteria and may be contaminated, for example, by excess manure in the hair samples. On occasion, samples will be rejected and new samples must be submitted. Most samples are shipped at room temperature. The testing process generally requires four to six weeks, with the results provided via email. Consult your lab or association for more information.
|Association||American Angus||American Hereford||American Simmental|
|Tissue*||Blood or tail hair with root bulbs||Blood or tail hair with root bulbs||Blood or tail hair with root bulbs|
|Price per sample**||$18||$38||$18|
|DNA Card (10 units)||$0.50 (blood)||$0.50 (blood)||$1 (blood) and $5 (hair)|
|Offer add-on test***||Yes||Yes||Yes|
*All three associations allow tissue sampling collections (ear notch); however, the price is higher compared to other sampling options. Refer to your association website for further information on tissue sampling and current pricing. ↵
** Prices updated March 2023. ↵
***Producers offer add-on tests such as the Coat Color Test, Arthrogryposis Multiplex (AM) Test, and the Neuropathic Hydrocephalus (NH) Test. Refer to your association website for the complete list. ↵
The newest technique used for parent verification is based on single nucleotide polymorphism (SNP) testing, which has greater accuracy compared to formerly used tests such as the single tandem repeat (STR) or microsatellite testing (MIP). One crucial factor is that both calf and parents should be tested with the same DNA technology (MIP and SNP). Most breed associations are retesting their animals with SNPs, which can cost from $15 to $25 per sample. Additional genetic testing that uses the same blood sample can be included as an add-on to parent verification. The add-ons can include complete genotyping, single traits, or genetic defects testing. Companies and associations offer special pricing based on the number of animals to be tested.
How to collect and ship blood or hair samples for genomic testing?
To collect blood samples:
- Record animal ID on the DNA card.
- Wipe the ear clean.
- Prick the vein in the animal's ear with a sterile needle (Figure 2, step 1).
- Touch the circle on the DNA card to the blood site in the ear (Figure 2, step 2).
- Fill the circle and allow the card to dry away from sunlight for 24 hours before mailing.
To collect tail hair samples:
- Record animal ID on the DNA card
- Pull from the tail switch "up and away" around 20 hairs with root bulbs (Figure 2, step 1).
- Place the bulb on the sticky flap. Hair bulbs must be present to perform the test (Figure 2, step 2).
- Press the side on top of the bulbs to seal the sides and trim excess hair to the edges of the hair card (Figure 2, step 2).
To ship the samples (both blood and tail hair samples):
Publication date: May 3, 2023
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