Improvement of dairy characters in farms and breeding value of the breeding bulls when assessing the quality of offspring

The article presents studies on comparison of the levels of precocity and milk productivity indicators of the daughters of Holstein bulls, who are evaluated for the quality of offspring simultaneously in two breeding plants of the Moscow region. According to the official ratings of breeding values, the bulls were divided into groups of "improving" and "worsening". The ratio of the daughters of the "best" and "worst" breeding bulls was 511:568 and 160:127 heads over the farms. It was determined which values of the differences in the "daughter – mother" indicators were increased in groups of officially evaluated bulls that received ratings of "improvers" and "deteriorators" according to the characteristics in these two breeding plants. The bulls being tested were fixed individually, and according to the number of pairs as the main ones. At the first insemination, the daughters of the "improving" group of bulls had 6.5–8.5 kg increased live weight of, but were relatively older by 0.36–0.6 months. According to the milk yield trait, the total yield of milk fat and protein, highly rated fathers in breeding plants were significantly inferior to competitors with low breeding value in milk yield by 688–1136 kg, according to the difference "mother – daughter" in the total yield of milk fat and protein per lactation – by 43.1–97.3 kg. In one of the farms, the "daughter – mother" differences in milk yield in all bull clusters increased by 599–1275 kg of milk; according to mass fat fraction (MFF) — by 0.02–0.20% and for mass protein fraction (MPF) — by 0.19–0.31%; in another farm, the increase in milk yield was by 43.8–1551 kg of milk and 0.05–0.13% according to the MPF. The daughters of the "worst" fathers in terms of MFF and MPF significantly outperformed the group of daughters of the "best" fathers in terms of "daughter–mother" differences by 35.6 and 61.7 kg of total milk protein and fat output over 305 days of lactation. At the same time, there were no significant differences between daughters and peers. The relativity of the official definition of the values of the breeding value of breeding bulls has been proved. It is proposed, regardless of the "commercial" and previously conducted estimates of breeding bulls, to take into account the indices of pedigrees and types of selection when breeding them. Conclusions are drawn about the significant influence of the factor and selection methods on the values of milk production traits; in order to save growing costs, it is proposed to optimize the live weight and age of insemination of heifers in farms.