Published from the IBBA Breed Improvement Committee
In mid-August of 2013, the American Angus Association released a statement concerning a new genetic condition that was identified in Angus cattle. This new defect is called Developmental Duplication (DD) and is genetically transmitted as a simple recessive gene. Dr. Jonathan Beever, University of Illinois, one of the world’s most renowned experts in the genetic identification of abnormal conditions in livestock, has spent several years reviewing this condition prior to submitting a final report to the American Angus Association. When the gene associated with DD is paired (two copies of same allele) in a mating, the results are either 1) high probability of early embryonic death or 2) calves born with multiple limbs. Other than an increase in the occurrence of mortality associated with dystocia, calves born with polymelia (born with extra limbs) often thrive, especially with removal of the limb or limbs at or soon after birth. Those animals identified as carriers (only one recessive allele) show no visible signs of the genetic condition and typically lead a normal life.
Based on research, Developmental Duplication is reported as a simple recessive trait like so many of the other genetic defects previously identified in cattle breeds around the globe. Again, this means an animal must carry two copies of the defective recessive allele in order to show this condition. Dr. Beever tested a large number of high-use AI Angus bulls and found approximately 6.5 percent carriers of the DD genotype. Dr. Beever’s lab also discovered the DD genotype in the Brangus genetic population.
With the onset of DD, it is clear the discovery of genetic conditions will be a part of the future for all breeds of cattle. Several of our sister breed associations have already dealt with previously identified genetic conditions for years. It is a high probability IBBA will deal with some of these same previously identified conditions in our breed population. We will be working in good faith with our membership in identifying genetic conditions, managing these conditions, and protecting the interests of our commercial customers while addressing financial concerns in future breed policies.
Commercial testing is now available to identify animals carrying the DD genetic condition. We cannot stress enough the importance of a well researched and educated approach within each individual breeding program. If properly managed, the breeding and financial impact from this DD condition can be kept to an acceptable minimum.
The International Brangus Breeder’s Association Board of Directors, along with our Breed Improvement Committee, is considering the ramifications of this condition, the best interests of the breed and our membership, the state of where the science of genetics is moving with respect to the early detection of genetic conditions, and our ability to manage such genetic conditions. We are working on policy for these genetic conditions while putting the infrastructure in place to deal with abnormal genetic conditions in our breed population. Our Board will ultimately determine how we will best deal with DD and will keep you abreast of our progress.
More detailed information on polymelia condition can be found at: