Genetic background of conformation defects in polish black-and-white Holstein-Friesian bulls – analysis of phenotypic distribution

Phenotypic distribution of 22 routinely evaluated conformation defects was analysed in a population of Polish Black-and-White Holstein-Friesian bulls, sired by different males. Some variation was observed in mean frequency of different morphological defects and in their severity. Large differences were found in frequency of conformation defects and in their number between groups of half-brothers. The most common defects in the bull population analysed were two types of leg defects: wide interdigital space and soft pasterns, which occurred in 199 and 70 animals, respectively. Wide interdigital space was most frequent in 4 groups of half-brothers, in which this defect affected more than 25% of the bulls. The least common defects were the defects of external genitalia, which were found in single animals. The only defect that did not occur was that of testes. The statistical significance of the phenotypic distributions obtained for bull conformation defects was confirmed using the chi-square test of independence and the Fisher-Yates exact test.