The American Angus Association this month announced it has discovered the presence of a new genetic disorder, identified by Australian researchers and the University of Illinois.
The disorder, called Developmental Duplication, is inherited as a simple recessive gene and can result in early embryonic death or polymelia – calves born with multiple limbs.
The incidence of polymelia has risen in Australian cattle populations over the last four years, which lead to the initial development of a test for the defective allele by Drs. Laurence Denholm, New South Wales Department of Trade and Investment, and Jonathan Beever, University of Illinois.
The test found that animals must carry two copies of the defective gene to show the condition. Beever also identified 72 carriers of the allele based on a test of 1,099 high-use artificial insemination Angus bulls.
The test also reveals an estimated 3% allele frequency, corresponding to a 6% carrier frequency among the sires tested. While the incidence of polymelia should be higher than what is reported, Beever estimates that the number of homozygous calves that survive to term is lower because of the potential for embryonic loss.
"As science progresses in this area, evidence is beginning to mount that there are a large number of genes in all populations of cattle that result in, at the very least, early embryonic death, when paired," an Angus Association statement noted, calling for improved tools and policies to address the situation.
"Certainly, improving our ability to manage defects by avoiding matings that will result in a significant possibility of defective genes being paired will be of value," the statement continued.
The Angus Association has also employed a task force to "consider the best interests of the breed and the membership" and has modified the Breeder's Reference Guide to reflect the new condition as of Aug. 14.