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GENETIC DETERMINATION OF REPRODUCTION LEVEL TRAITS IN DAIRY CATTLE BREEDING

Modern cattle selection programs are characterized by the increase of traits with a low level of genetic determination. This change is associated to a technical means of verification capabilities (automated milking systems, behavioral video surveillance systems, control of rumination process, etc.), the success of genomics when selection based on genetic markers requires additional controls over the phenotypic changes. But the basic selection remains the production economy-based selection process. Recently, more features related to reproduction and productive longevity or animal health have been included in this group. A study was carried out on the effects of genetic and environmental factors on the voluntary waiting period, the open days and milk productivity. A new feature was identified – the insemination period which was defined as the difference between the length of the open days and the waiting period. Investigations were carried out on Holstein cows (605 heads in total), the average milk yield which amounted 8777 kg. The majority of the primary information was the data of the Uniform Agri program, which analyzed using variance and correlation-regression analysis. Weak probable impact of the «father» factor on the 305-day milk yield of lactation (11.5 %), the open days (5.4 %) and the insemination period (5.2 %) was identified. A positive, reliable and weak correlation was found between lactation milk yields and service period (0.115, p ≤ 0.01.), and between service period and voluntary waiting period (0.257, p ≤ 0.01). The dependence of the length of the service period and the voluntary waiting period on paratypic factors such as the age of cow’s lactation and the month of their calving is investigated. As such, a tendency to reduce the length of the open days and the voluntary waiting period in cows with each subsequent lactation. It is found that the length of the voluntary waiting period was the largest in cows that calved in November, March, May, and the shortest – in August. At the same time, cows that had calved in March was the largest the open days, and with calving in February – the shortest. It was concluded that the possibility of using the value of the insemination period in the selection programs. The possibility of using the traits of the level of reproduction in the selection programs has been proven.