Influence of stud bulls on the daughters’ productive qualities

The objective of the study is to determine the influence of sires on the productive qualities of daughters at Novotayozhnoye OJSC. Objectives: to analyze the productivity of daughters of bulls and mothers of daughters of bulls; to determine the prepotency of bulls using different methods. The productive indicators for the first lactation of daughters of Holstein sires were analyzed: Chulym 21548 (n = 222), Deposit 19125 (n = 389), Radon 11764 (n = 168). The daughters and their mothers were assessed by milk yield for the first 305 days of lactation, mass fraction of fat and protein. To assess the influence of sires on the produc-tive qualities of daughters, the variation coefficients were calculated as the degree of homogeneity of the productive indicators of daughters, and the correlations between the indicators of daughters, the sires being assessed and their mothers. The assessment of the productive indicators of the cows showed that the highest milk yield for the first 305 days of lactation was in the daughters of Radon – 6050 kg. The highest mass fraction of fat was in the daughters of Chulym (4.04 %), the daughters of Radon were distinguished by a high mass fraction of protein (3.13 %). The milk yield of the mothers of Radon's daugh-ters was 5416 kg, the mass fractions of fat and protein were 3.9 and 3.05 %, respectively. The daughters of all bulls have variation coefficients for milk yield of 12.6–14.1 %, and uniform and low for the mass frac-tions of fat and protein in milk (2.5–2.69 and 1.16-2.55%, respectively), which indicates the prepotency of the bulls for these indicators according to L.K. Ernst (1968). According to S.A. Ruzsky (1967), the prepo-tency for milk yield in Deposit and Radon is high (r = 0.06–0.07). In terms of fat mass fraction, Chulym is highly prepotent. In terms of protein mass fraction, the most prepotent bulls are Deposit (r = 0.06) and Chulym (r = 0.10). When determining the prepotency of bulls, we recommend using the method of S.A. Ruzsky (1967), due to the fact that it makes it possible to select producers with both higher and lower prepotency. Specialists of Novotayezhnoye OJSC are advised to use bulls Deposit 19125 and Radon 11764 to increase milk yield of cows. It is advisable to use bull Chulym 21548 to improve fat content in milk. Milk protein content can be increased by using bulls Chulym 21548 and Deposit 19125.