Estimates of genetic parameters for fertility traits of Australian Holstein-Friesian cattle

Fertility data collected on 17131 Holstein-Friesian cows from 158 dairy herds in Australia were used to estimate heritabilities for and correlations among several fertility traits using a sire model. Pregnancy rate (PR), survival (Surv), calving interval (CI), calving to first service interval (CFS), insemination rate (coded as 1 if a cow received a service or 0 otherwise) (InsemR) and first service non-return rate (FNRR) were the main traits analysed in a sixtrait model. Among the traits, CFS had the highest h2 (0·13) and FNRR had the lowest h2 (0·01). Genetic correlations among the traits were higher than environmental correlations in all cases. The genetic correlations of PR with InsemR, FNRR, CFS, CI and Surv were 0·74, 0·79 and –0·84, –0·57, and 0·67, respectively. The genetic correlation between InsemR and CFS was high (–0·95) indicating that they almost measure the same trait. Analysis of data from cows that did not return to service after the first service despite not being pregnant (so-called ‘phantom’ cow syndrome) showed that the syndrome is not heritable. The relatively high genetic correlation of PR with traits such as CI and Surv that can be extracted from milk recording data and CFS, FNRR and InsemR that can be obtained from mating data suggests that routine genetic evaluation of sires for daughter fertility based on these traits can be implemented in national selection programs.