New Zealand ranks dairy bulls and cows by Breeding Worth (BW) for their expected ability to breed profitable and efficient replacements. The ranking compares across ages and breeds. Currently the traits included in Breeding Worth and the associated economic values are:
Breeding Worth = (Protein x $8.18) + (Milkfat x $1.81) + (Milk Volume x $-0.097) + (Liveweight x $-1.63) + (Fertility x $7.23)+ (Residual Survival x $0.14) + (Somatic cell x $-38.61).
Source: NZAEL February 2015
In general the higher the BW of the bull the more profit likely to be produced by his offspring. The top bulls in New Zealand are now in the $200-320 BW range. Some care needs to be taken when using this figure, however, as the economic weights used in its calculation are specifically based on the New Zealand economic environment.