Genetic conditions or defects are caused by DNA abnormalities and are present in all species, including beef cattle, with over 400 genetic conditions having been identified across different beef breeds, ranging from lethal genetic conditions where calves do not survive, through to genetic conditions with minimal economic impact.
Ten different genetic conditions are currently recognised within Angus Australia’s Regulations, with Arthrogryposis Multiplex (AM), Neuropathic Hydrocephalus (NH), Contractural Arachnodactyly (CA), and Developmental Duplications (DD) being the conditions that people will be most familiar with.
The commitment of Angus Australia’s members to the management of these genetic conditions has proven to be very effective, and the number of cases reported of animals affected by each respective condition is now not only very low, but the incidence of carrier animals within the registered Australian Angus population for each condition has reduced considerably (see Figure 1).
As a consequence, the number of animals being DNA tested for each genetic condition has reduced dramatically in recent years (see Figure 2), and the management of genetic conditions now relies considerably on Angus Australia’s weekly gene probability analyses, and the determination that untested animals are free by inheritance.
While this situation is a great credit to Angus breeders, it does introduce some risk as the gene probability results being published for untested Angus animals are reliant on the accuracy of an animal’s pedigree information, and the existence of any historic pedigree errors will result in the calculation of potentially misleading gene probability results.
This risk was highlighted in September 2018 when the American Angus Association released a notice announcing that a widely used AI sire in the United States, 3F Epic 4631, had been identified as being a carrier for NH, despite being previously thought to be free by inheritance.
While of little consequence in Australia as semen from 3F Epic 4631 had not yet been imported, Angus Australia has also recently had several similar cases, albeit of considerably less consequence, where animals previously thought to be free by inheritance have subsequently been identified as being a carrier for one of the genetic conditions.
So while the incidence of carriers for known genetic conditions within the registered Australian Angus population now sits at relatively low levels, it is critical that Angus seedstock breeders remain vigilant in the management of genetic conditions within their breeding program.
The Angus Australia Board has introduced a new Regulation from June 1st, 2019 that requires any AI sire who is born after 1/1/2018 to be tested for any genetic condition for which a genomic test is commercially available before it will be possible to register their progeny. This currently includes the 4 most common genetic conditions, AM, CA, DD and NH, along with dwarfism (DW), alpha mannosidosis (MA), osteopetrosis (OS) and oculocutaneous hypopigmentation (OH).
Additionally, while not a requirement of registration, Angus seedstock breeders are strongly encouraged to ensure all sires joined in paddock matings, along with all donor dams, are at a minimum, DNA sire verified, and ideally fully DNA parent verified, prior to use in their seedstock breeding operation, along with being DNA tested for the 4 most common genetic conditions, being AM, CA, DD and NH.
Conducting DNA parentage verification, along with DNA testing for these 4 genetic conditions reduces the risk of inadvertently using a carrier within your breeding program that would otherwise incorrectly assume to be free by inheritance based on the gene probability analysis results.
DNA parentage verification is best conducted for sires and donor dams by genomically testing with either the Angus GS or HD50K for Angus products. Both products are available for a cost of $51.45 (inc GST). Testing for AM, CA, DD and NH can be added when testing with either product for an additional cost of $24.75 (inc GST).
Consideration should also be given to testing sires joined in paddock matings and donor dams for the 4 other genetic conditions for which a genomic test is available, being DW (Dwarfism), MA (Alpha Mannosidosis), OS (Osteopetrosis) and OH (Oculocutaneous Hypopigmentation), along with other genetic traits for which genomic tests are available, such as red gene, myostatin, and homozygous polled.
Testing for these 7 traits can be added when testing with Angus GS for an additional cost of $16.50 (inc GST), meaning the full suite of 8 genetic conditions and 3 genetic traits can be added to Angus GS for a total additional cost of $41.25 (inc GST).
Take Home Messages
To further discuss the management of genetic conditions in either a seedstock or commercial Angus breeding program, please contact staff at Angus Australia.