Developmental Duplication (DD) has been identified in both American and Australian Angus cattle populations. Brangus and Ultrablack carry, at minimum, five-eights Angus genetics, so the Brangus breed has joined in identification of DD through DNA testing. Town Creek Farm wholly supports DNA testing and the approach taken by International Brangus Breeders Association.
"We want to be proactive on all issues and want to provide our customers with complete transparency," says Town Creek Farm owner Milton Sundbeck. This open book policy is one that has served Sundbeck and his companies well in the past. "We have always been upfront with our customers and will continue to be."
The discovery of DD came in August 2013, when a new autosomal (Chromosome 26) recessive mutation was identified in Angus cattle with polymelia (supernumerary limbs) by Prof. Jonathan Beever of the University of Illinois, Urbana, using samples from Australian calves with polymelia that were sent to him in 2011 and 2013. The mutation causes a single amino-acid substitution at a locus that has been conserved without change throughout the evolution of vertebrate and non-vertebrate animals.
DD is caused by a simple recessive genetic mutation. Keep in mind that carrier animals carry only one copy of the gene—the animal itself is NOT affected with the condition. In order for DD to be expressed phenotypically, both parents must contribute a copy of the gene. Cattle are identified as carriers are either DD Affected (DDA), meaning they carry two copies of the gene (one inherited from each parent); or DD Carrier (DDC) meaning they are carriers with one copy of the gene (inherited from one parent). Once cattle test clean, statuses change to DD Free (DDF).
Every living creature carries recessive genes. When mating's occur, genes from both parents are passed on to the offspring. However, dominant genes are primary key concepts in inheritance.
Keep things in perspective. It is important to understand that DD testing, to date, has rendered a very low occurrence of the condition in our Brangus population. As we analyze Town Creek Farm genetic populations, some sires have been identified as having known carriers of DD in pedigrees. Town Creek Farm is aggressively testing sires and donor dams as of this writing. As results are received, they will be posted on this webpage.
Most importantly, DD has been around for decades. Genetics within the cattle populations of Town Creek Farm (TCF), it's predecessor, Cow Creek Ranch (CCR), and Town Creek Farm Bull Production Partners, along with commercial cattlemen using TCF and CCR genetics, have reported NO incidences or suspected occurrences of DD in progeny.
DNA technology has enhanced and accelerated our ability to identify mutations and test for genetic conditions that were previously unidentifiable. This will continue to be the case as we move forward. It's now an accepted reality that we are able to identify more recessives and diagnostic DNA-based tests quicker and more cost effectively than in the past. In the end, the cattle industry stands to gain a lot by advancements in DNA technology as a way to manage risk and improve quality.
If you have any concerns or questions, please contact Joy Reznicek at Town Creek Farm, 205.399.0221. We encourage you to embrace DNA technology, not only does it allow us to free up know carriers in pedigrees, it has also enhances genetic progress.
Occurrence of clinical presentation is suggested to be low. It's Mother Natures way for abnormal embryos not to survive full term, so, according to Dr. Beever, "calves presenting at birth with DD disorder are 'rare events that survive embryonic death.'"
Having stated that, there are several phenotypic clinical presentations of DD. Calves can sometimes be born with a phenotype known as polymeric, which results in duplication of limbs, extra legs if you will. Extra legs vary in size and may or may not grow in proportion to the host calf.
Another presentation is Axial Duplication. Newborn calves with an acephlia conjoined "twin". There may or may not be one or more legs projecting form the conjoined "twin"
Intradural Embryogenic Teratomas: The clinical presentation is a congenital soft tissue mass on the dorsal midline, with or without signs of spinal cord dysfunction due to cord tethering or compression.