Estimation of heritability coefficients for gestation length and calf birth weight in the population of Holstein cattle in the Republic of Serbia

The gestation length in cows and the birth weight of calves significantly influence the course and difficulty of parturition in dairy cows, thereby having a considerable impact on the economic efficiency of cattle production. The aim of the study was to determine the phenotypic variability and heritability coefficients of these traits, as well as the potential for selection for these traits in the dairy cattle population in the Republic of Serbia. The research included 1,348 Holstein-Friesian cows, which calved 4,247 times between 2007 and 2016 on a farm near Belgrade. The significance of the factors was analyzed using the GLM procedure of the SAS statistical package. The variance components were calculated using the REML methodology within the VARCOMP procedure of the SAS statistical package (version 9.4). The average gestation length in the studied population was 278.5 days, while the average birth weight of the calves was 37.1 kg. The study showed a high statistical significance of parity, year, calving season, and calf sex for both traits, except for the effect of calving season on calf birth weight, where the season had a statistically significant effect. Gestation length showed a low heritability (0.018), whereas the heritability coefficient for birth weight was determined to be 0.355.