Cattle industry can manage genetic abnormalities
Historically, in addition to recording pedigree and performance information and providing genetic predictions, the performance programs at cattle breed associations have monitored and managed genetic abnormalities. While there has been relatively little news on that subject for the last decade, several defects recently have emerged. Some are in popular lines of cattle, and they often warrant the attention of breeders and commercial producers.
"By our account, there currently are about 10 different abnormalities in various stages of active management by different beef breeds," said Kent Andersen, Ph.D., executive vice president of the North American Limousin Foundation. "You might think of those stages of management as initial investigation, DNA-test development, implementation of genotype testing and associated policy, and--ultimately--effective eradication through continued testing and selection."
"Fortunately, most of those defects are rare, effectively have been eliminated, are nonlethal, or are under aggressive management via DNA-based diagnostic tests and pedigree analysis," Andersen added. "We know other abnormalities exist, but the industry has isolated them, or they are of such extremely low frequency that they are not threatening."
As a service to the cattle industry, NALF has compiled a table of genetic abnormalities under management by beef breed associations and posted it on the Web. A link to the table is on the association's home page (www.nalf.org). As it shows, breed associations have worked behind the scenes over the years to monitor abnormalities and address those that represent even relatively minor concerns.
The Web page also describes the inheritance, tracking and avoidance of genetic abnormalities.
With one presumed exception, the listed defects are of genetic origin and result from a simple recessive mode of inheritance. That means both parents of affected progeny are carriers or affected themselves - assuming the abnormality is nonlethal. With that type of inheritance, without results from DNA or progeny tests, animals that are free of the defective gene (normal) generally are indistinguishable from those that are carriers of the abnormality.
"For commercial producers, the trick to avoiding calves with lethal or performance- threatening abnormalities is never to mate a carrier bull to a carrier female," Andersen explained. "The first and easiest line of defense is to use only bulls that are free of the relevant defect in a given population."
"Mutations that cause abnormalities always will be a reality of the livestock business," he said. "Fortunately, with advances in genomics technology and thoughtful management by associations and breeders, we can mitigate the adverse effects substantially."
The North American Limousin Foundation (www.nalf.org), headquartered in Centennial, Colo., provides programs and services--including genetic evaluation of 5,000 active sires--to more than 4,000 members and their commercial customers. The Limousin breed and its Lim-Flex hybrid lead the beef industry in muscle-growth efficiency and ideally complement British breeds.