Breeding value calculation changes afoot
Matamata dairy farmers need to be aware that liveweight breeding values for dairy cattle change this month after data analyses was 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), was implemented on February 16.
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 two- year- olds, which skews the calculation,’’ NZAEL Manager Dr Jeremy Bryant said.
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,’’ he said.
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 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 came into ary 16.
‘‘ NZAEL updates economic values every year, in order to keep aligned with market signals.’’
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. Crossbred herds will be intermediate between the two breeds,’’ Bryant said.
effect on Febru-
CHANGES: Liveweight breeding values for dairy cattle change this month.