Weighting game gets a boost

Liveweight breeding values of Holstein Friesians are seen generally to increase.

Liveweight breeding values for dairy cattle are to improve as a result of data analyses carried out by NZ Animal Evaluation Limited (NZAEL), a wholly owned subsidiary of DairyNZ.

Changes to these breeding values and the flow-on effects for the overall measure of cow and sire genetic merit, Breeding Worth (BW), were implemented this month.

These improvements are focused around the conversion of liveweight information into a mature weight equivalent.

"Historically, this conversion has been done within the liveweight animal evaluation model but, over time, the information that we receive has become heavily weighted towards data for 2-year-olds, which skews the calculation," says NZAEL manager Dr Jeremy Bryant.

The new method converts all weights to a mature equivalent before the data enters the liveweight animal evaluation model.

"The aim of the NZAEL research was to improve the accuracy of genetic prediction for liveweight, which then leads to a more accurate BW for dairy farmers," says Bryant.

The research has been undertaken over the past year and has been reviewed by the Standing Advisory Committee of NZAEL, which includes leading geneticists from New Zealand, and has been approved by the NZAEL board.

The effect of this improvement to liveweight breeding values will be seen across all animals but particularly when comparing breeds. The liveweight breeding values for Jersey and crossbred animals generally decrease, and those for Holstein Friesians increase.

The routine updates of economic values in BW also come into effect from February 16.

"NZAEL updates economic values every year in order to keep aligned with market signals," says Bryant.

This year, moderate changes are seen in the value assigned to fat and protein yield. These come from a combination of a falling milk price, as well as slight changes to the calculation of milk volume penalties and flow-on effects for fat and protein yield.

The combined effect of the liveweight changes and economic value update mean that, on average, the BW of herds will reduce.

"Farmers with predominantly Jersey dairy cattle will see a slight increase in herd BW and farmers with predominantly Holstein Friesian dairy cattle should notice a decrease in herd BW," says Bryant.

"Crossbred herds will be intermediate between the two breeds."