EVALUATION OF VARIABILITY OF POPULATION-GENETIC PARAMETERS OF BODY STRUCTURE MEASUREMENTS OF BLACK-AND-WHITE DAIRY CATTLE COWS

In a herd breeding two breeds – Ukrainian Black-and-White Dairy and Holstein own selection, a study was conducted to study the correlation of variability of body structure measurements of first-born cow cows with milk yield and the level of their heritability. The results of the study showed that the level of positive correlation coefficients and their reliability serve as evidence that the productivity of first-born cows of the Ukrainian Black-and-White dairy and Holstein breeds significantly depends on the height at the withers (r = 0.311 and 0.414) and rump (r = 0.297 and 0.377), chest depth (r = 0.384 and 0.422), latitudinal measurements of the rump (r = 0.321–0.376 and 0.341–0.392), body length (r = 0.297 and 0.339) and chest girth (r = 0.351 and 0.396). Therefore, the selection of cows at the age of the first lactation of the experimental herd by measurements will indirectly ensure the effectiveness of selection by milk yield. At the same time, it will be more effective among Holstein cows. The variability of the coefficients of heritability of the sexes of the body structure of first-born cows is observed both within the estimated measurements and between breeds. However, the coefficients were higher in Holstein animals. The share of hereditary variability in the total phenotypic measurements of first-born cows of the Ukrainian Black-and-White dairy breed was within 16.2–30.7%, while in Holsteins it was higher – 19.6–38.4%. The obtained significant positive correlation between the sexes of the body structure measurements and the size of the litter and the sufficient level of heritability of the measurements of first-born cows are motivating factors for the effective selection of dairy cattle by exterior.