Abstract
The analysis included 433 daughters of 10 bulls, calving for the first time in the period from 2007 to 2014, on 6 dairy farms of the Agricultural Corporation Belgrade AD. Fixed factors included in the model were the effects of the farm, year of calving and calving season, and as a random factor the impact of the bull sire. The observed fertility properties on the basis of which breeding values were calculated were the number of days of gestation, the age at the first insemination, the service period duration and the calving interval. Bulls were ranked on the basis of these properties and using the Spearman correlation coefficient, the degree of agreement between the ranks was determined. According to the breeding values calculated by using the Best Linear Unbiased Prediction (BLUP) method, the sire 1517 was best ranked for the trait duration of service period (-34,94 days) and the calving interval (-36,14 days), relative to the average of daughters. The effects of the farm and year of calving showed no significance (p>0.05) except on the duration of the gestation. The effect of the calving season showed a very high significance (p 0.05).
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