There is no “one size fits all” strategy for managing genetic conditions. Before embarking on a management strategy producers should consider:
– the economic impact of the condition
– the frequency of the condition within the herd and/or breed
– the availability and cost of DNA tests
– researching the genetic condition status of any animals being brought into the herd
– legal obligations about disclosing the carrier status of sale animals
– the Angus Australia regulations
Generally, the management of genetic conditions can be broken into two components.
In simple terms, the incidence of animals affected by the genetic condition can be managed by avoiding mating carrier cows to a carrier bull. This may be relatively easy to manage in seedstock herds, but can be extremely difficult in commercial herds where limited pedigree records are kept. For this reason it is recommended commercial herds, or seedstock herds that have conducted minimal testing should only use bulls that are tested free or expected to be free by inheritance.
The genetic condition status of all registered animals can viewed from Angus Database Search and is displayed on Angus Australia registration certificates.
Managing the frequency of carrier animals is important in seedstock operations. Where available, the use of DNA testing to determine if an animal is either free or a carrier for a genetic condition broadens the options for breeders looking to manage or eradicate the mutation. Angus Australia runs a weekly gene probability analysis for the 4 major genetic conditions (AM, CA, DD and NH), to calculate the risk of particular untested individuals being carriers. The results of this analysis are displayed for each animal on the Angus Database Search facility, while PDF reports and .CSV files containing results for each individual Angus Australia member, are made available through Angus ONLINE.
Seedstock breeders should carefully consider and develop a management strategy that will be used to manage each genetic condition. Some examples of management strategies are as follows:
– Conduct strategic DNA testing of highly influential animals (eg. sires, donor dams, prominent dams) to calculate the probability of animals being carriers, and better identify the “at risk” bloodlines. Further testing can then be conducted to better isolate the carriers present in the herd.
– DNA test at risk animals in the breeding herd to identify carrier animals. Rather than being sold, carrier females can be retained for use as recipient dams in embryo transfer programs.
– Continue to use carrier animals in the breeding program by joining them only to tested free sires/dams and testing the progeny. As outlined previously, mating a carrier to a free animal will result in 100% of calves being unaffected by the genetic condition, with 50% of the resulting offspring being free of the condition and 50% being carriers. This approach is of particular benefit when the carrier animal is of high genetic merit and the producer wants to utilise these desirable genes in the breeding program.
– Only use sires that are tested free or are expected to be free by inheritance to ensure the incidence of the condition does not increase. This is a common approach for genetic conditions of low economic impact.
– Angus Australia regulations require all AI or ET sires, born after the 1/1/2018, to be tested for all genetic condition monitored by the society.
In all situations, if carrier animals are sold, full disclosure of their genetic condition status should be provided.