Focus on Genetic Holds and Defect Testing
Genetic defect testing and genetic holds are two of the most common subjects ASA’s DNA department handles. This month’s article will explore the most commonly-asked questions within this subject.
When is genetic defect testing required?
For all AI sires, herd sires, and donor dams, if risk is present on TraitTrac and not cleared by test or pedigree, the progeny will go on genetic hold. For example, if a herd sire is a population risk for CA, his progeny will go on genetic hold, which means EPDs and registration certificates are held until the risk is cleared by test or pedigree. However, if a female has a single-born calf (not embryo transfer), and she is tracked for CA, her calf will not go on genetic hold, assuming the sire doesn’t cause a hold. If this calf is a bull kept back for breeding, the risk will be passed on and his progeny will go on genetic hold.
When is genetic defect testing suggested?
ASA always suggests testing for a potential genetic defect in breeding animals when there is a risk for the genetic condition. This means if an animal’s TraitTrac shows Carrier in Lineage, Documented Carrier, Documented Carrier in Lineage, or Population Risk, testing is suggested. Test as far back in the pedigree as possible to get the most out of each test. For example, if you have an eight-year-old half Angus cow, at risk for CA, and she has five daughters in production, test the older cow as it will clear the risk for all of her progeny if she is CA free, and their subsequent progeny.
Why does ASA require genetic defect testing?
Like humans, cattle as a species have always carried a variety of genetic defects. Before science advanced enough to test for these defects, producers relied upon visual appraisal and tracking trends in pedigrees to eliminate abnormalities. Dwarfism in Hereford cattle is a well-known example of this — Decades ago when the abnormality became an issue, there wasn’t a way to test for it and producers lost a significant amount of money getting it under control. The important thing to keep in mind is that an animal may carry the defect and not express it, meaning it may take several generations but without testing and selection, it could wreck a producer’s bottom line. Crossbreeding and more varied pedigree selection makes genetic defects less of a concern for commercial producers. Members are always welcome to do any defect and trait testing through another lab if they choose (parentage and genomics are never accepted from outside labs, however). If members test for genetic conditions or traits with a different lab, they are encouraged to submit those test results to ASA so Herdbook can reflect the test results.
What is the difference between genetic defect testing and trait testing?
Genetic defects are considered to have deleterious effects on the production of beef cattle. Traits are simply physical expressions of a gene that alter the appearance of the cattle but don’t have serious economic loss with the affected cattle due to health reasons. For example, Pulmonary Hypoplasia with Anasarca (PHA), is a defect that when expressed, causes calves to be born dead with underdeveloped lungs. Oculocutaneous Hypopigmentation (OH), is a trait that when expressed, causes cattle to have light-colored irises and a chocolate coat color.
Is ASA’s genetic defect policy the same as other associations?
Each respective breed association has its own policy regarding genetic defects. Most follow similar guidelines for tracking genetic defects. For example, if an Angus animal’s parents are both tested free for DD, the animal is recognized as Parentage Free for that defect and ASA accepts that status. However, ASA must see documentation from other breed associations showing that the animal is either free by parentage, pedigree, or test, to clear the animal of defect risk.
- Created: 20 October 2019
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