Agricultural News
Genetics in the Genomics Era - Improving the Accuracy of Selection
Tue, 03 Aug 2021 08:29:52 CDT
Mark Johnson, Oklahoma State University Extension Beef Cattle Breeding Specialist, offers herd health advice as part of the weekly series known as the "Cow Calf Corner" published electronically by Dr. Peel, Mark Johnson, and Paul Beck. today Johnson is talking about genetics in the genomics era.
This week's article is intended for registered, seedstock breeders in the purebred sector of cow-calf production. As we approach the time of year that spring calving operations will be weaning, selection decisions will be made regarding how many heifers should be developed as replacements, for marketing or culled. Likewise, which bulls should be developed as potential herd sires to use or sell. These decisions impact marketing success, how we will utilize feed resources and the accuracy of these selection decisions dramatically impacts how much long-term genetic improvement we will make. With this in mind, using available DNA testing technology can cost effectively accelerate reaching our breeding goals.
What can we learn from DNA testing?
By working with your breed association to order the tests, submitting DNA samples and obtaining the lab results, current DNA testing technology can: 1) verify parentage, 2) determine genotypes for simply inherited, qualitative traits, and 3) identify genes having an additive genetic effect on the variation of quantitative, polygenic traits which result in higher accuracy, Genomically Enhanced Expected Progeny Differences (GE-EPDs). This information is typically available within a few weeks of when DNA samples are submitted yielding genetic information that would otherwise take generations of calf crops to obtain.
Determining genotypes for qualitative, simply inherited traits, when dominant/recessive gene action is occurring at a locus, can identify homozygous or "carrier" genotypes of animals with the same phenotype. For example, the horned/polled phenotype where the polled allele is dominant to the horned allele means that polled cattle can be either homozygous polled or heterozygous polled. If our breeding objectives include producing polled calves, parents with the homozygous polled genotype will sire/produce nothing but polled calves. Traits like coat color and most of the identified genetic defects are also simply inherited.
GE-EPDs increase the accuracy of selection for traits influenced by the thousands of genes. This would include traits like calving ease, weaning and yearling weights, carcass traits and maternal performance.
Breeders should contact their breed association for information and proper procedures for submitting DNA samples. DNA samples can be submitted in the form of blood (in purple topped tube or on a DNA card), tissue samples from an ear notch, hair follicles collected from the switch (from cattle weaning age or older) and straws of semen. Additional information on DNA sample collection is available on the OSU Beef Extension You Tube Channel or OSU Fact Sheet ANSI-3174.
Prices for DNA testing have come down dramatically over the past several years. Information on available tests and prices available through your breed association should be taken into account in considering the return on investment. Identifying genetically superior animals early in life not only can increase the effectiveness of selection in your program, it also provides more reliable estimates of genetic potential to customers purchasing registered, pedigreed seedstock.
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