Angus Australia announced the discovery of a new recessive genetic condition called Developmental Duplication or DD in August 2013. The condition, also commonly known as Polymelia, is known to occur across many species and breeds of cattle.
According to Dr Parnell there have been about 20 total cases of animals displaying developmental duplications reported to Angus Australia over the last four years and the condition can be found in both Bos Taurus and Bos indicus animals, plus other species and in humans.
“Given the small number of cases reported, the commercial impact of the condition in a typical commercial herd is expected to be minimal”.
“Much bigger losses occur in every herd each year due to non-genetic animal health issues. Most genetic diseases can be easily managed by ensuring that only bulls of known genetic background that have been adequately tested are used in commercial herds”, he said.
“An important part of the breeding program for any registered seedstock operation is the identification and elimination of undesirable recessive genes in the population. The ‘recessive’ nature of these conditions means that in most situations they are rarely observed, and only occur when an individual animal inherits two copies of the ‘recessive gene’, from either side of its pedigree. When an animal contains just one copy of the gene it is considered a ‘carrier’ and does not display the particular condition”, said Dr Parnell.
“The bloodlines carrying the DD gene, and other known recessive genetic conditions, have provided great benefits to the Angus breed over past decades through increased growth, fertility and carcase performance” said Dr Parnell.
“It is simply a matter of identifying and eliminating carrier animals from the population and continuing to utilise the positive attributes of these genotypes” he said.
Dr Parnell suggests that the best way of eliminating the risk of these known genetic disorders in commercial herds is to only purchase registered bulls from breeders with a management program in place to eliminate known recessive genetic conditions from their herds.
“The greatest risk to the commercial sector from recessive genetic conditions comes from unregistered bulls with unknown genetic background”, Dr Parnell said.
For Dr Peter Parnell’s full article and other information on DD please refer to www.angusaustralia.com.au
In 2008 there was a massive over reaction in both the US and Australia to the discovery of AM recessive condition in Angus cattle. Most astute breeders now understand that the Angus breed will continue to discover more recessives as new DNA technology now allows us to develop diagnostic DNA based tests more quickly and cost effectively in the past.
In our view, the information provided by these tests is useful as it helps us and our clients continue to multiply out the top performance bulls in the breed and maintain high levels of genetic progress. The reality is, all bulls carry recessive genes, some good, some indifferent and some not so good and potentially lethal. The DNA tests help us reduce the frequency of the bad genes so we can continue to use these top sires and their sons. It’s only likely that the more highly used bulls will have DNA testing to identify these as you need to have a reasonable number (> 10 head) of affected calves to try and identify the causal mutation and then establish the DNA test to identify carriers.
Breeders claiming to be “free of recessives” are simply not providing accurate information. The truth is, their bulls carry just as many recessives as any other and commercial breeders ‘jumping bloodlines’ to avoid recessives will suffer more from loss of genetic gain than any economic loss as a result of having an affected calf. Our clients who calve down tens of thousands of calves every year in Australia have reported under five cases of DD. We have only had one confirmed case last year and only two other suspected calves that died at birth. We reported the calf to ASA and sent DNA samples to Angus Australia, which were then sent to Dr John Beever in the US.
We support the development of DNA testing and the approach being taken by Angus Australia. The testing is a major financial issue for seedstock herds like Lawsons Angus but it is important that commercial clients understand that it is an insignificant economic issue for them. Far bigger challenges are faced in developing a high quality breeding programs and operating an agricultural business.
Lawsons Angus maintain focus and discipline to optimise the balance between inbreeding and genetic progress using two very important genetic strategies
The very few reports in our herd and in our clients’ herds across Australia confirms both these strategies that working in tandem, are doing a great job managing inbreeding at both seedstock and commercial levels.
Our advice is for commercial clients to continue to focus on making good decisions on what bulls they select and develop a simple management plan that incorporates the principles of Sire-Mate where you avoid close up matings. This way you will continue to make predictable and rapid genetic progress and minimise any risks or damage that can result from higher inbreeding rates through loss of fitness traits (like reproduction) and occurrence of recessive disorders like DD, AM, NH, CA. This also applies to the many others disorders that are in existence but that may or may not be documented and be able to be managed through DNA testing.
Our other key message is to keep things in perspective. This is more an issue for seedstock suppliers to deal with as part of our quality assurance program. It is not a major economic issue for commercial herds. The same approach applies for all the recessive genes currently identified.
For another perspective I would encourage any breeders to listen to Mark Gardiner’s comment on You-Tube.
Gardiners Angus Ranch in Kansas, USA is one of the most successful animal breeding operations in the world and a partner of Lawsons Angus. This video, also available from the Gardiners Angus website, provides Mark Gardiner’s perspective on the new Development Duplications (DD) mutation that has been recently identified in the Angus breed.
Lawsons Angus supports Gardiner’s view that the recessive mutation will be successfully managed using the data available in the beef industry’s most extensive and world class database, as other recessive conditions in the breed have to date.
If our clients have any questions about their Lawson Angus genetics and DD please call Harry anytime.