Population Genetic Features of Calving Interval of Holstein-Friesian Cows Bred in Hungary.

Calving interval (CI) data (N = 37,263) from 17,319 cows born 2008-2018 in six herds were assessed. The data were made available by the National Association of Hungarian Holstein Friesian Breeders in Hungary. The effects of some genetic and environmental factors, population genetic parameters, breeding value (BV) of sires, and phenotypic and genetic trends of the CI were estimated. The GLM method was used for studying different effects on the CI. BLUP animal model was used for heritability (h(2)) and BV estimation. Linear regression analyses were applied for the trend calculation. The mean of the CI was 412.2 ± 2.0 days. The h(2) of the CI proved to be low (0.07 ± 0.01 and 0.08 ± 0.01). There were relatively high differences among the sires in the estimated BV. Based on the phenotypic trend calculation, the CI of cows showed decreasing direction by an average of 1.80 days per year (R(2) = 0.94; p < 0.01). In the case of genetic trend calculation, the average BV of sires in the CI has decreased -4.94 and -0.31 days per year (R(2) = 0.91 and 0.41; p < 0.01).