Sub-indexes for bulls of Holstein breed in the Czech Republic

Sub-indexes were constructed for bulls of the Holstein breed according to groups of production traits - production index for milk (IPH), sub-indexes for reproduction (IRH), longevity (IDH), health resistance (IOH) and fitness (IFH). Every index for selection for a group of traits applies all available information - breeding values for traits of milk performance, fertility and linear type trait classification. The sub-indexes were compared with the total index (SIH). The accuracy of total selection index (SIH) was 69.30%, the accuracies of the other indexes were as follows: IPH 83.32%, IRH 56.04%, IDH 9.80%, IOH 15.57% and IFH 9.86%. All of the indexes were standardised to have the mean 100 and standard deviation 12. Simplified index ZSIH was developed as a sum of IPH, IRH and IDH; its correlation with the total index is r = 0.992. If IPH is used, the values of secondary functional traits decrease. The use of IDH, IOH and IFH results in a decrease in milk performance. Selection differences, i.e. changes in breeding values at various intensities of selection according to some indexes and breeding values for kg of milk and kg of milk proteins, were tested on the basis of breeding values in a sample of the domestic population of bulls. The production index was compared with production indexes used in other countries. Correlations between production indexes were higher than r = 0.790.