Dairy cattle breeding have always occupied and will continue to occupy one of the leading places in the agro-industrial complex in our country. The most eff ective method of improving existing breeds according to opinion of a number of scientists is selection in line breeding. At the same time the evaluation of breeding sires by the quality of offspring is the cornerstone of breeding work. The purpose of the research was to analyze the influence of breeding sires, as well as their linear affiliation on the economically useful characteristics of first-calf heifers under specific conditions of maintenance and use. An analysis of the milk productivity and reproductive traits of first-calf heifers of different origin by sires and different line belonging has been presented in the article. The results of intra-linear selection and crosses of genealogical lines and their influence on the productive and reproductive traits of first-calf heifers have been evaluated. The research was carried out in LLC “Green Lines-Kaluga” of the Kaluga region. It has been established that for fixing in the genotype of the offspring of plentiful milk and fat milk in purebred breeding, it is necessary to use the following sires: Aragon 2102, Tabor 1292, Lira 2047, Phlox 1448, Chudny 1167, Yalik 397, Tabun 1277, as well as intra-linear selection in the line of Montwick Chieftain 9567929 and crosses of lines in combinations: Siling Traijun Rocket 252803 – Reflection Sovereign 198998 and Wes Ideal 933122 – Siling Traijun Rocket 252803. In order to reduce the age of the first insemination of maternal stock we recommend using a combination of lines: Wes Ideal 933122 – Montwick Chieftain 9567929, Wes Ideal 933122 – Reflection Sovereign 198998, Montwick Chieftain 9567929 – Wes Ideal 933122, Montwick Chieftain 9567929 – Reflection Sovereign 198998 and Siling Trijun Rocket 252803 – Wes Ideal 933122.
The existence of linear selection and the quotient lifting property
