Breeding for fertility is reducing calving interval
Calving Interval can be reduced by up to 10 days in just one generation by using the best Fertility Index bulls available, reports Marco Winters, geneticist for MDC breeding+.
His call for farmers to pay more attention to breeding in addressing issues such as fertility and health comes just over a year after the Fertility Index was launched and with new knowledge of its influence on the national dairy herd.
The latest data from the MDC confirms that for every point increase in a bull's Fertility Index, an average improvement in his daughters' calving interval of around half a day is achieved.
"That may not sound much in isolation," recognises Mr Winters, "but the important thing to remember is that the effects of a breeding decision are permanent and cumulative over the generations."
The index is published on a scale of around -10 to +10 and therefore the data shows choosing the best over the worst bull available could potentially improve the next generation's Calving Interval by as much as 10 days.
"In practice, and taking a typical situation of an average UK herd, which would have a Fertily Index of zero, the best bull could improve Calving Interval by five days," says Mr Winters.
Since the average bull in the top 100 PLI (Profitable Life Index) list has a Fertility Index of -2.5, farmers are urged to seek out the figures for themselves, as not all companies publish this information as a matter of routine.
"All farmers should be asking their AI reps about Fertility Index and trying to avoid bulls with a very negative score," recommends Mr Winters.
"Of course, the obvious and immediate solution to most health and fertility problems is through management and feeding but failure to address these issues when breeding decisions are made will inevitably make high production dairy cows more difficult to manage."
He concludes: "We've all seen how quickly undesirable traits can magnify over the generations and there's no reason why the reverse can't be true when it comes to selecting for fertility.
"No one is suggesting farmers weren't already selecting fertile cows within their own herds but until the launch of this index they had no idea - often until it was too late - whether they were choosing a bull which transmitted poor fertility to his daughters.
"As with all non-production indexes, we're not suggesting fertility is used as the primary selection criterion, but if all else is equal, we'd recommend choosing the bull with the higher Fertility Index."
