Efficiency of line breeding in a high-yielding herd of dairy cattle

Research on the influence of line heredity on signs of milk productivity of cows was conducted in the herd of “Chereshenki” LLC of the Novgorod-Siverskyi District of the Chernihiv Region. The progeny of breeder bulls of eight genealogical formations of black and spotted cattle of different genotypes were evaluated, taking into account the origin of the lines from the father's side. Milk yield (kg), content (mass fraction, %) and output of milk fat and protein (kg) for 305 days of the first-third and better lactations were taken into account. The results of the evaluation of the lines proved the reliable variability of the signs of milk productivity of their offspring in the dynamics of lactations. The highest weight gain of first-born cows of the Eleveishna line (8547 kg) was significantly higher compared to representatives of the lines J. Besna by 431 kg (Р < 0.05), Bella – by 570 kg (Р < 0.001), Marshall – by 848 kg (Р < 0.001), Valiant – by 871 kg (Р < 0.001), Starbuck – by 673 kg (Р < 0.001) and with the herd average – by 265 kg (Р < 0.001). The highest content of fat in milk was found in the offspring of the J. Besna line, whose representatives exceeded the cows of the other lines by 0.03–0.13 % (Р < 0.05–0.001) and the herd average by 0.10% (Р < 0.001). The offspring of the Eleveyshna line (317.9 kg) were in the lead in terms of milk fat yield, with the advantage of representatives of other lines with a significant difference of 7.3–25.3 kg (Р < 0.01–0.001). The variability of the mass fraction of protein in milk within the lines was 3.21–3.27 %. The highest protein content was found in the offspring of bulls of the J. Besna line (3.27 %). The difference compared to the peers of the rest of the lines was 0.01–0.05 % with reliable confirmation with the offspring of the rest of the lines and the herd average (Р < 0.01–0.001). The highest level of milk protein belongs to the offspring of first-born cows of the Eleveishna line (275.2 kg), which is higher compared to representatives of the rest of the lines with a difference ranging from 4.8 (daughters of the Chifa line; P < 0.01) to 25.8 kg (daughters of the Marshall line; P < 0.001). The dynamics of the variability of the signs of milk productivity of cows of the evaluated lines according to the data of the second, third and best lactations changed in the direction of their improvement without changes in the leading positions of the lines.