Official calving ease indexes for Holstein and Friesian sires will be published with the DairyCo breeding+ proof run next month alongside several changes which have been designed to help dairy farmers make more informed breeding choices.
The indexes will be expressed on a scale of about -4 to +4 around a breed average of zero, with positive figures indicating that calvings are predicted to be easier than average and negative figures predicting more difficult calvings.
This is the first time independent calving ease indexes have been produced in the UK, and follows an industry-wide collaboration and the analysis of some 400,000 calving records. These have been gathered by British farmers as either part of their regular milk recording or as part of their participation in progeny testing.
The two genetic indexes which result from the study – Direct Calving Ease (dCE) and Maternal Calving Ease (mCE) – together give a complete picture of a bull’s ‘calving performance’.
“Direct Calving Ease gives a prediction of the ease with which a calf by that sire will be born and Maternal Calving Ease predicts the ease with which a daughter of that sire will give birth,” explains geneticist Marco Winters, director of DairyCo breeding+.
Direct Calving Ease is likely to be of most interest in the first instance, and is naturally going to be important when breeding maiden heifers,” he says. “But it shouldn’t be ignored in older cow matings either, where it would always be wise to avoid bulls which are likely to produce very difficult calvings.
“But attention should also be paid to Maternal Calving Ease, as long-term selection for dCE without any regard to mCE could set up problems for the future.”
This relationship will be familiar to cattle breeders, who are likely to associate easy calvings with smaller calves, but whose smaller calves sometimes go on to have difficult calvings themselves.
“As part of a broader breeding strategy, I’d recommend selecting primarily for Profitable Lifetime Index (PLI) and using the Calving Ease indexes - as well as other fitness traits - as secondary criteria, with careful judgement made on a case-by-case basis about their relative importance,” says Mr Winters.
Commenting on the work behind the index, Dr Mike Coffey from SAC, who led the research team said: “The index is an important development for the dairy cattle breeding industry and highlights the importance of milk producers taking part in national recording. We’ve only recently had sufficient data to undertake the background research, but now that it’s complete, I’m delighted that DairyCo breeding+ will routinely include Calving Ease indexes in the genetic evaluations it publishes on an ongoing basis.”
“The AI companies’ own proofs which were used in the past were certainly helpful, but it’s far better to have industry-wide figures expressed on a common UK scale,” adds Mr Winters. “This gives farmers easy access to the calving ease information from just one list, without having to trawl through the plethora of individual bull catalogues.”
For the time being, dCE and mCE will remain as stand-alone indexes although they may be included within PLI at a future date.
Announcing the new indexes ahead of the January proof run, Mr Winters concludes: “There’ll be a lot of new information to get to grips with when the proofs are published next month and we hope it will be helpful for those with an interest in cattle breeding to familiarise themselves with some of the changes before they take effect.”
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