Designing different options in Ukrainian black-and-white dairy cattle population selection
The studies reveal that livestock breeding farms in Kiev region have enough bull-improvers received from valuable sires. The average breeding value of the bulls parents was + 492 kg milk. At the same time, 24.6% of bulls parents had no assessment for the offspring quality. Reducing the number of parents bull from 134 to 5 results in genetic progress increase in milk yield of 30.7 kg to 45.2 kg of milk per cow per year, since the most valuable sires will fall in this category according to their breeding qualities. Hard repair culling of the remount bulls not conforming the breed will provide an increase in the average breeding value in the cows parent group that allows to use high performance improvers bulls in stock breeding. For example, the average breeding value of parent cows increased from 222 kg to 240.5 kg of milk and the number of bulls evaluated on the offspring quality - from 44.6% to 48.7% due to semen of 18 bulls with low breeding value and bulls received from unvalued fathers and mothers of bulls with low productivity culling in Bila Tserkva livestock breeding farm. While selecting two bulls (primary and secondary) from each line into a group of parents bulls, their number would increase to 32 heads, and genetic advances would decrease to 14.1 kg of milk and the breeding value of the sires to + 412 kg accordingly. Designing selection options indicated that under the existing structure of the population the maximum of 20% of the active cows population should be inseminated with the sperm of untested young bulls, considering the fact that that the number of cows inseminated effectively with one proven bulls should be in the range of 120-150 heads, and 80% of cows population should be inseminated with the semen of the sires evaluated on the offspring quality. Because of small number of cows of active part of the population, young bulls assessment on the offspring quality should be carried out on 30 effective daughters that will enable to obtain a reliable estimation of breeding values and test up to 20 bulls annually on a small number of cows. This will reduce costs on bulls assessment and increase selection of bull sires in the group, which will increase the rate of the population genetic improvement. If the portion of the active part of the population inseminated by the proven bulls increase to 50%, the bulls evaluation reliability will increase, though thare will be decrease in the portion of the population that should be inseminated with the semen of bulls selected for the offspring quality which will reduce genetic progress. Thus, under fulfilling these conditions, under intense and rigorous selection of bull-sires the rate of the population genetic improvement will increase 2.5-3 times - from of 0.51 to 1.52% per year. The study shows that under cows population average milk yield of less than 4000 kg of milk for the first lactation, it is necessary to reduce the sperm bank of the verified bulls to 25 thousand of doses, since the cost of the selection program do not cover the expences of the product obtained. Genetic progress will make 25.3 kg milk per cow per year, and the program cost - about 20%. With an average yield of 5500 kg milk in first lactation cows the genetic progress under the same breeding activities will be 42.7 kg milk, and sperm bank increase to 30 thousand doses would increase the genetic progress to 45.8 kg of milk and the program cost return - to 40%. With the increase in milk yield of 6000 kg of milk in first lactation cows the genetic progress will be 52.1 kg milk and programs efficiency will make 58%. In this case, sperm bank on proven sires may be increased to 40 thousand doses, which will increase the genetic progress to 60.4 kg milk and selection program profitability will increase to 72% per year.