Dependence of productive qualities of cows of brown Swiss breed on their physiological devel-opment

The brown Swiss breed of cattle, which is currently being bred in the Smolensk region for dairy and meat productivity, is of interest from the point of view of its production feasibility and competitiveness, and the biological properties of livestock. The research was carried out in a breeding reproducer for the breeding of brown Swiss cattle of the Smolensk region, in the conditions of the farm, the age of fruitful insemination, physiological development, linear affiliation and productive qualities were analyzed (n=384). According to the terms of fertilization, the animals were conditionally divided into three groups: - early-maturing 46 heads (12%) live weight of the first insemination 329 kg, medium-maturing 191 heads (49.7%) live weight 388 kg and late-maturing 147 heads (38.3%) live weight 429 kg. The genealogical structure of the analyzed livestock includes descendants of the related groups Meridian 90827 (46.3%), Concentrate 106157 (25.4%), Master 106902 (25.4%) and line Laird  71151 (2.9%). The highest milk yield and fat for the first (4520 kg) and highest lactation (5022 kg, 3.97 %) in late-maturing animals. The group of first-calf cows of medium precocity in terms of milk yield occupies an intermediate position (4334 kg). The difference in live weight between the third and first groups is significant (P<0.05). There were no significant differences in milk fat and protein between the groups of cows. From these studies, it follows that the larger the live weight at the first insemination, the more productive they are.