MILK PERFORMANCE OF CROSSBRED COWS OF THE SLOVAK PIED BREED WITH DAIRY BREEDS

A total of 15,814 lactations of the cows of the Slovak Pied cattle and crossbred cows of this breed with dairy breeds which calved in 1983-1991 were evaluated in this paper. The least-squares method was used for statistical analysis. The effects of herd and calving year and the effects of genotype group and year x genotype group interaction in the crossbreds were included in models of analysis of covariances. Lactation days and age at first calving in the first-calves and lactation number in the cows were concomitant variables. Milk production per lactation, fat percentage in milk and fat production per lactation were dependent variables. Tabs. I and II show the basic variation-statistical data on the investigated parameters. The crossbreds of all the investigated hereditary blood shares are evaluated in total. Milk production of this group was higher by 10% and/or 9% in the 1st, 2nd and other lactations in comparison with the Slovak Pied dairy cows. Tabs. III to IV show the results of analyses of covariances. The factors herd and year participated in variability of all the investigated parameters statistically highly significantly (P < 0.01). The effect of genotype group in the crossbreds was statistically highly significant (P < 0.01) for milk and fat production and insignificant for fat percentage. Lactation days had a statistically highly significant (P < 0.01) effect on variability of milk and fat production, but they did not influence fat percentage in milk statistically significantly. Age at 1st calving statistically significantly influenced milk and fat production in 1st lactation in the crossbreds, and fat percentage and production in the pure first-calvers. The effect of lactation number on variability of milk and fat production was statistically highly significant (P < 0.01) in both investigated groups. Tabs. VII and VIII show the estimates of mean values of the particular genotype groups. Milk production in 1st lactation was higher by 170-460 kg in the crossbreds, depending upon the blood share of dairy breed. In second and other lactations the differences were 135 to 355 kg milk in favor of the crossbreds. All differences from the Slovak Pied breed were statistically highly significant (P < 0.01). The crossbreds of all groups had the lower fat percentage in milk.