Inbreeding and relationship in Polish Black-and-White sires.

The aim of the study was to analyse inbreeding and relationship in the Polish population of Black-and-White sires. Data were pedigrees of 25,036 Black-and-White sires born from 1960 through 2000, divided into subsets of 11,447 proven and 13 589 unproven sires, and their 38,228 ancestors, altogether 63,264 animals. Average inbreeding coefficients were about 0.3% for both subsets of sires. Mean relationship coefficients ranged from 0.1% in all animals to 0.7% in the subset of proven sires. Positive time trends in inbreeding coefficients were observed when the subsets of sires were divided into 5-year intervals according to the year of birth and in terms of Holstein Friesian gene contribution.