high fertility bull

High fertility bulls can double impact in low fertility herds

AbacusBio consultants Hadyn Craig and Peter Amer have been working together in a DairyNZ-led study to investigate the worth of high fertility bulls.

The results have shown that high fertility bulls, when used over low fertility herds can have almost double the impact, as compared to high fertility herds.

“This means that if you have poor fertility in your herd, using a bull team that is strong for the trait can make a large difference,” Hadyn explains.

However, in high fertility herds, high fertility bulls were found to have a limited impact on the six-week calving rate. This means that if a herd has good fertility already, there is little benefit in targeting the best bulls for fertility – just avoid poor performing bulls.

“Targeting high fertility bulls would take around five years to have a real impact on herd performance, as it is the daughters of the high ranking bulls who would have improved fertility – rather than the bull himself,” Peter remarks.

Having said that, farmers who are experiencing a fertility problem in their herds, often have to compromise on the overall Breeding Worth (BW), as high BW bull teams are likely to have only a reasonable level of fertility.

BW is an animal selection index that ranks animals based on their ability to breed profitable and efficient replacement heifers.

The index combines eight traits identified as having economic importance to dairy farmers including fertility, which receives an emphasis of around 15%.

“Of course, management is always a key player, things like having cows in good condition at calving and making sure there are no underlying health issues remain very important, but this research shows that bull selection is also having a huge impact.”

The research is part of a seven-year programme, the Pillars of a Sustainable Dairy System, which looks at dairy cow fertility, and is jointly funded by DairyNZ and the Ministry of Business, Innovation and Employment (MBIE) with aligned funding from AgResearch.

This article is adapted from a Dairy Exporter article by Karen Trebilcock.