Recently the American Angus Association recognized a new simple recessive genetic defect referred to as Developmental Duplication (DD). The defect results in calves being born with extra limbs or in early embryonic death of the affected embryo. The AAA has decided to allow cattle affected with DD to continue to be registered, due to the evolving scientific advances in the field of genetics, breeders’ ability to manage such conditions and the likelihood that the scientific community will continue to identify genetic conditions in all breeds with increasing frequency in the future.
Popular sires carrying the defect include B/R New Design 036, Bon View New Design 1407 and GAR Predestined.Since we are on the subject, it is important to note that line-breeding will neither cause nor prevent the occurrence of a genetic defect. Line-breeding simply increases the chance that a defect, already present in a heterozygous state within the parents, will be displayed. Therefore, line-breeding decreases the chance of an undesirable characteristic such as a defect being passed on from generation to generation without being identified.