Phenotypic differences in productive in-dicators of Sychevka breed cows

The aim of the study is to determine the influence of paratypic factors (farm management conditions, age at first calving, calving season) on the phenotype of Sychevka cows. The productive and reproductive qualities of cows of the Toreador 3032 (114 heads) and Reflection Sovereign 198998 (21 heads) lines from the Rybkovskoye and Vostok breeding farms in the Smolensk Region, analogs by linear affiliation with a productive activity period of 2018–2022, were studied. In the Rybkovskoye farm, the livestock was used for a longer period. From the Toreador 3032 line – by 7.9 months, their lifetime milk productivity is 4,437 kg higher. From the Reflection Sovereign 198998 line – by 65.9 months with a lifetime productivity of 30,702 kg higher. The milk fat and protein content of animals in farms varied by 0.1 %. Reproductive quali-ties were determined by the lifetime fertility index calculated using the K. Wilcox formula. In the Vostok farm it had a higher value (96.9–118.6 %). To determine the impact of the “age of first calving” factor, the livestock was conditionally divided into five groups: 25 months and younger; 26–28; 29–31; 32–34; 35 months and older. It was revealed that it is inappropriate to use early (up to 25 months) and late (35 months and older) age of first calving in cows of the Toreador 3032 line for obtaining high-yielding ani-mals. The most favorable age of first calving for the milk productivity indicator is 26–28 months (Toreador 3032 line) and 29–31 months (Reflection Sovereign 198998 line). The highest lifetime milk productivity was obtained from cows of the Reflection Sovereign 198998 line (37,945 ± 7,588 kg) at the first calving in summer, from the Toreador 3032 line (14,766 ± 1,695 kg) in autumn. According to the data obtained using a two-way analysis of variance without repetitions at a significance level of p = 0.05, the age of first cal-ving, taking into account the season of calving, did not affect the lifetime fertility index.