[Differences in susceptibility of cows, in half-sisters by the same sire to mastitis].

The set of 9,555 cows, Bohemian Spotted breed, was studied if the sires contributed significantly to higher resistance, or on the contrary to susceptibility, of daughters to mastitis. The study was performed in 67 groups of half-sisters. Statistically highly significant (P less than 0.01) and significant (P less than 0.05) differences were proved as regards the frequency of bacteriologically positive and negative half-sisters in 36 groups as compared with the frequency ratio of positive and negative animals in the population. The daughters of 20 sires were more influenced in the positive sense, i. e. they suffered from mastitis less frequently than the daughters of 16 sires with a higher occurrence of the disease.