[Incidence of mastitis in cows of various breeds and their crosses-- estimation of the heredity of this disease].

In a large set of cows (24,165 head), consisting prevailingly of Bohemian Pied breed, Black Pied Lowland and Holstein breeds, and of their crosses, significant differences in the incidence of mastitis were proved. Mastitis was demonstrated by the bacteriological findings in milk. The lowest mean incidence was recorded in the cows of the acclimatized Bohemian Pied breed (8.0%). As observed in the examined population, the increasing genetic proportion of solely dairy breeds results in higher demands on the environment, and the susceptibility of animals to mastitis usually increases. In three-breed crosses of this set, mastitis was found in 699 animals, i. e. in 25.4%. With respect to mastitis prevalence, a heritability estimate was performed on the basis of the first and second lactation using the method of alternative characters. In the Bohemian Pied breed, the heritability estimate was ĥ2 = 0.17 +/- +/- 0.08, in the Black Pied Lowland breed ĥ2 = 0.28 +/- 0.14.