HERITABILITY AND REPEATABILITY OF FERTILITY TRAITS OF HOLSTEIN-FRIESIAN BULLS MONITORED IN PROGENY TESTING

To test the variability of fertility traits of Holstein-Friesian bulls monitored in progeny test, reproduction data of 342 cows, daughters of 15 bulls were used. Cows have been in production in seven farms of Agricultural Corporation "Belgrade" in the period from 2004 to 2012. The study included the following fertility traits: the average calving age, service period and calving interval. To analyze the influence of genetic and non-genetic sources of variability a mixed model with random effect of bull - sire, the fixed effects of farm, year, season and order of calving was used. The sire is present in variability of all the observed fertility traits (p