EVALUATION OF COWS AND BULLS BASED ON THE INTENSITY OF DEVELOPMENT IN DIFFERENT PERIODS OF HEIFERS' BREEDING
In order to spot an opportunity of selection based on features of heifers development a statistical analysis, including the study of their relation to cows productivity, was carried out. A significant relation of milk yield to a live weight during all the periods of development was determined. Regression analysis indicates an increase in milk yield of 6.4 and 6.3 kg, respectively, with an increase in heifers' live weight of 1 kg at the age of 10 and 12 months. Heifers development intensity analysis was performed with the use of a computer program “Selective and genetical statistics - the All-Russian State Research Institute of Genetics and Breeding of Farm Animals” when evaluating the heifers is based on live weight (breeding value) in different periods of their development. It was found that live weight of 56.7% of first-calf heifers was equal to or exceeded the live weight of their herdmates by 30.0 kg or more at the age of 10 months. The superiority in live weight at the age of first insemination over herdmates was 8 kg, outyielding was 33 kg of milk. A similar trend is observed in the classification of first-calf heifers based on breeding value based on live weight at 12 months. According to our data the influence of the bulls on daughters' live weight at birth is equal to 18.2, to 12.8 at 10 months, to 12.4 at 12 months, to 9.2 at 18 months and to 5.4 at the period of the first insemination. Manufacturers differ in daughters' milk yield, and more productive of them surpass their herdmates in live weight at different periods of development. For example, moderate superiority in live weight at 10, 12 months and at first insemination of bulls' daughters - 44033 Ullimulli and 7960576 K. Toivo (+8, +11, +6, and +7, +8, +3 kg) in the presence of 69.6, 65.2% and 68.0, 60.0 of heifers with superiority in live weight over herdmates at 10 and 12 months is followed by a high milk yield of the daughters of 8459 and 8533 kg exceeding the level of herdmates by 109 and 105 kg of milk, respectively. However, it should be noted that the group of animals with superiority in live weight over herdmates generally has a higher productivity among the daughters of one bull. Consequently, the performances of heifers' development intensity - breeding value based on live weight at 10 and 12 months, can be used as a criterion for selection and early forecasting of the level of milk cow production.