Population parameters of productive characteristics of the black-and-white cattle breed in the Vologda oblast

The research was carried out in order to determine the main selection characteristics: variability, heritability and repeatability of productive features in the modern population of cattle of the Black-and-White breed in the Vologda Oblast. These population characteristics give an idea of the possibility of successful selection and further improvement of dairy cattle. On the basis of calculation of variation coefficients it was established that the selection by milk yield Cv = 23.4% will be the most effective in the controlled population. The coefficient of heritability for milk productivity is h2 = 0.30, which indicates that the mothers can pass the feature to their offspring with a high degree of success. The coefficient of repeatability on milk yield for the cows of the Black-and-White breed for the 1st, 2nd and 3rd lactation was 0.74-0.75. A high degree of repeatability of the selection feature indicates the possibility of effective selection. It was found that there exists a high, reliable (P ≤ 0.001) correlation r = +0.79 between milk productivity of cows for the first 100 days and milk yield for 305 days of lactation, which indicates the possibility of selecting animals for herd formation at an earlier stage. Selection for butterfat percentage and protein percentage should be conducted on complex indicators: milk fat and milk protein. According to these indicators, the level of variability is higher Cv = 23.3-23.5% than the weight content of fat and protein in milk Cv = 4.4-7.9%. The correlation between milk yield and weight content of fat in the milk of cows of the Black-and-White breed has a negativevalue r = -0.19; therefore, when milk yield increases, then the fat content in the milk decreases. These parameters of productive features should be used in selection and breeding to improve dairy cattle management efficiency.