Impact of diferent types of selection on the milk productivity of Kostroma breed cows

The article studies the influence of homogeneous and heterogeneous selection on the milk productivity of first-calf cows (milk yield, fat and protein content in milk). The object of research is cattle of the Kostroma breed. The research methods were zootechnical, population-genetic and analytical using computer programs IAS “SELEX” Multifarm and BON-MilkRegion. The modern cattle breeding base in the Kostroma region is represented by three breeding plants and two breeding reproducers. In 2022, the Karavaevo Breeding Farm JSC received 9,297 kg of milk per cow, the Minskoe LLC pedigree reproducer received 7,371 kg of milk, and the Rodina collective farm, Gridino and Agrofirma Planet LLC received more 6000 kg of milk. Record milk yields reach 15,000 kg of milk or more in 305 days of lactation. The following lines have been identified as promising in the Kostroma breed: lines Ladka 2537 and Kursa 3722, related groups Master 106902, Meridian 90927 and Concentrate 106157. To improve the productive qualities of dairy cattle, it is necessary to use both intraline selection and cross-lines, taking into account their compatibility. In breeding farms, using homogeneous selection, high productivity indicators were obtained: in terms of milk yield - from first-calf heifers of the related groups Laird, Concentrate and Meridian, in terms of fat and protein content in milk - Laird and Ladka. With heterogeneous selection, the best combinations were identified across farms.