Maternal longevity is a key trait missing from selection indices that characterise profit for a ewe flock or a beef cow herd.
Young said B+LNZ Genetics had research projects looking at genetic merit for maternal traits in both beef cows and ewes, including longevity.
He said equivalent work in beef cows was less advanced but was also important economically. B+LNZ Genetics would be working with beef genetics service providers, researchers and bull breeders to develop measures of “maternal longevity” for beef cattle.
SIL introduced a system for coding the reasons why ewes exit the flock. In mid-2009 many SIL breeders have been using this system for recording. Once exit code data has been gathered for a number of years they will be able to develop better genetic analysis for longevity to produce a more advanced version of the breeding value.
Young said this was because the SIL ewe exit codes allowed them to better characterise commercial longevity by separating out the reasons why ewes exit a ram breeding flock as opposed to a commercial flock.
“This is important because ram breeders cull some ewes for different reasons compared to commercial farmers.”
For example, a ram breeder could cull a ewe because she failed to rear lambs two years in a row or because she had poor breeding values, something a commercial farmer won’t know for an untagged ewe in a large flock.
In 2009 Ovita funding initiated development of a longevity breeding value for sheep using a “bare bones” approach based on when ewes cease to contribute production information in ram breeding flocks. In the past 12 months the project has progressed to the point where SIL will introduce a breeding value for longevity based on this definition.
This interpretation does not require any information on the reason why a ewe exited the flock.
Young said SIL would roll it out after testing on more flocks was complete. This would be as a research breeding value (rBV) for SIL breeders to evaluate and provide feedback on.
What’s in a name?
A variety of terms are used to define commercial longevity such as stayability or productive lifetime or (maternal) survivability.
Geneticist Mark Young said SIL was working with breeders to choose a term meaningful to them and their clients. Since SIL commonly talks about “survival” in the context of lamb survival to weaning it was unlikely to use “ewe survival” to remove any chance of ambiguity.
Young welcomed feedback on this issue from commercial farmers as well as ram and bull breeders. Contact him at silhelp@sil.co.nz or 0800-silhelp.
