Some big changes will be happening when DairyCo publishes the bull proofs next month, most important of which is the introduction of official calving ease indexes, which have never been published in the UK before. With the addition of further 'all-breed' information - allowing comparisons (using a conversion formula) to be made between bulls of different breeds - there's likely to be something of interest to a wide cross section of milk producers, including those involved in crossing a variety of dairy breeds.
But the calving ease indexes are considered the most important addition for January 2010, and represent the culmination of an industry-wide collaboration which began in 2008. The project was heavily funded by Defra, had additional support from the Scottish Government, DairyCo, NMR, CIS, Holstein UK, Genus ABS and Cogent, and was undertaken by SAC.
Involving the analysis of some 400,000 calving records, gathered by British farmers as either part of their regular milk recording or as part of their participation in progeny testing, the study assessed the calving performance associated with 6,000 Holstein and Friesian sires.
The result has been to create two genetic indexes for Calving Ease - Direct Calving Ease (dCE) and Maternal Calving Ease (mCE). With the indexes giving a prediction of the ease with which a calf by that sire will be born (dCE) and the ease with which a daughter of that sire will give birth (mCE), a complete picture of each bull's 'calving performance' can be gauged through the two indexes.
Expression will be 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.
"In reality, the Direct Calving Ease proof is likely to be of most interest," says geneticist Marco Winters, director of DairyCo breeding+. "This is obviously going to be far more so when breeding maiden heifers, where choosing easy calving sires is clearly an important consideration. 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.
"As with most of the fitness traits, I'd recommend using Calving Ease as a secondary consideration and use careful judgement on a case-by-case basis about its relative importance.
"It's also important to be aware that long-term selection for Direct Calving Ease without any regard to Maternal Calving Ease could set up problems for the future.
"It's well known that the two traits are inversely correlated, which means that as you select for good dCE you are likely to worsen mCE, so it's important that farmers pay attention to both of these figures," adds 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 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.
"The national evaluations will also facilitate breeding to improve calving ease longer term and will pave the way for its possible inclusion in Profitable Lifetime Index (PLI) in the future."