Genetic factors of increasing selectional traits in the breeding herds of the black-and-white cattle in the Orel region

The scientific work presents the results of breeding in 5 herds of Black-and-White breed from the Orel region. The research showed that the heritability estimate (h2) by milk yield for 305 days of the first lactation on the farm "Streletskoye" (n=717) was 0.468, it was 0.440 on the farm "Kurakinskoe" (n=322), it was 0.240 on the farm "Red Star" (n=181), it was 0.260 on the farm "Agrofirma Mtsenskaya" (n=523) and it was 0.422 on the farm named after Michurin (n=471). The heritability estimate of milk fat content (h2) in these herds was 0.005, 0.346, 0.060, 0.156 and 0.104 respectively. The repeatability factor of the growth intensity (rw) varied within the limits from 0.305 to 0.615-0.671, and consequently, the level of genetic determination of the live weight of heifer calves from birth to 18 months reached 61.5-67.1%; environmental factors were at the average of 32.9-38.5%. The percentage of the Holstein breed on the studied farms was from 59.8±0.6 to 76.8±0.7, which confirmed the high degree of crossing of the sectioned livestock (Cv=10.8-31.0%). In the herds the milk yields of lactation for 305 days and the fat content in milk were positively correlated (r=+0.05-0.27). Due to the additive heritability and successful consolidation of stud bulls in the studied herds positive genetic correlations were found between the some breeding traits of dairy productivity. High heritability estates, the desired phenotypic and genotypic correlations allow us to conclude that further progress can be made on selection criteria in the population. According to the results, in future the superiority of heifer calves over their mothers at the level of 261 to 1146 kg of milk and fat in milk from 0.02 to 0.18% can be expected in other breeding herds of Black-and-White cattle in the Orel region.