Actuality of research data is in contribution rate of growth of genetic progress according to main economic traits in Ayshire populations at the cost of conducting correlative- regression analysis and study of influence factors, as a preparatory phase in development of selection index for selection of animal units into selected groups. Study sample of cow heifers (n=12821), which are offsprings of 232 servicing bulls from 13 farms, is modified to normal distribution with the help of R-studio program (on control of events, emergence, removal of empty and impossible values). Calculation and analysis of selective- genetic parameters of economic traits are conducted, and also impact assessment of genetic and paratypic factors on realization of economic traits of local cattle population of Ayshire breed in Leningrad region for the period from 2014 to 2018. Animal milk production was 6848 kg with fat mass percentage and protein 4,07 and 3,29 %. We established lowering of MOP duration and reproductivity coefficient and fertility index (RC and FI). Multiregressional model was formed including into formula percentage of fat, protein, live weight and service period. It was established that with fat increase for 1 % milk yield will decrease by 15,3 kg, but with increase of protein on the same value- for 107,8 kg of milk. The most accurate influence on studied economic traits had father factor (14,97 – 41,58% ***). Consequently, with the aim to achieve positive result in population development of Ayshire cattle it is necessary to use bulls, having high genetic potential of milk yield and reproductive qualities.

Проведены исследования линейной оценки признаков экстерьера первотелок айрширской породы (n572), являющихся дочерьми 21 быка, на основании которых рассчитаны индексы композиции вымени (UDC) и качества конечностей (FLC), полифакторные индексы ПЭИ2 и ПЭИ6, коэффициент ранговой корреляции Спирмена между используемыми индексами и племенной ценностью быков по удою (ПЦВСКП). Отсутствие достоверной связи между UDC и FLC с ПЦВСКП препятствует улучшению экстерьера потомков при отборе по внутристадной оценке. Достоверно высокая взаимосвязь выявлена между UDC и финальной оценкой экстерьера, индексами ПЭИ2 и ПЭИ6 0,745, 0,706 и 0,710, соответственно. В процессе моделирования алгоритмов отбора быковпроизводителей установлено, что с введением 25ного отбора быков по ПЦВСКП вместе с увеличением самой оценки на 155 кг достоверно (P0,001) повышается индекс ПЭИ2 на 48 (P0,001), а при отборе 10 производителей на 247 кг и 81 при P0,001, соответственно. В результате отбора по ПЭИ2 получены высокие и достоверные селекционные дифференциалы (P0,001) по удою 430 кг, финальной оценке 0,67 баллов, индексу ПЭИ2 102, а также по внутристадной племенной ценности 108 кг. При моделировании двух вариантов отбора по UDC и FLC проведена сверка 5 лучших быков, при которой выявлено, что дочери производителей Лабри и Носто по сравнению со сверстницами при потере продуктивности на 115 кг достоверно улучшают показатели вымени на 0,3 (P0,05), конечностей на 1,1 (P0,001) и финальную оценку на 1,0 балл (P0,001).Studies were carried out on a linear assessment of the exterior first calving cows of Ayrshire breed (n572), which are the daughters of 21 bulls, on the basis of which the UDC and FLC, the productively exterior indices PEI2 and PEI6, the Spearmans rank correlation coefficient between the indices and the intraherd breeding value (BVin) bulls was calculated. Improvement of the exterior in the selection of assessments due to the lack of reliable correlation between the UDC and FLC with the BVin. A reliable high correlation was found between the UDC and the final assessment of the exterior, the indices PEI2 and PEI6 0.745, 0.706 and 0.710, respectively. It was found that with the selection of 25 of bulls, the assessment itself increases by 155 (P0.001) and the PEI2 increases significantly by 48 (P0.001), while selecting 10 of bulls by 247 and 81 (P 0.001) respectively. The selection of PEI2 gave high and reliable breeding differentials (P0.001) for a yield of 430 kg, for a final assessment of 0.67 points, for the PEI2 102, for BVin 108. In the selection by UDC and FLC 25 of bulls were identified: Labry and Nosto. The daughters of these bulls with a loss of milk yield by 115 kg reliably improve the udder by 0.3 (P0.05), feet and legs by 1.1 (P0.001) and the final assessment by 1.0 point (P0.001).

Research is focuses on the possibility of using udder dairy composite (UDC) and feet and legs composite indices (FLC) as indicators of the reasons for the culling of Ayrshire cows based on the results of their exterior assessment after the first calving. The processing included data on the exterior assessment and the reasons for their cull of 855 first calving cows. Almost all the correlation coefficients of indices with the classification assessment of exterior features were positive and reliable. The UDC is most correlated with the classification of the udder (0.614***) and the total score (0.535***), the least — with the dairy strength (-0.126***). The FLC is highly correlated with the classification of legs (0.940***), with the total score(0.529***), low negative and unreliable with a dairy strength (-0.033). The indices are interconnected at 0.223***. The ranking of UDC and FLC by level revealed an incomplete coincidence of the point complex assessment of some signs of the exterior. The ranking of UDC by level revealed an increase in the scoring classification of all signs of the exterior, the FLC has a mismatch. In culling cows due to limb diseases the FLC was negative (-0.44 ± 0.31) and low compared to other groups. The value of UDC with diseases of the udder is -0.06 ± 0.08. In other animals, these were neutral or positive values. Cows with negative values of both indices were identified in each group of diseases. For example, in groups with udder disease and metabolic disorders, the number of such cows is almost the same 26.0 and 26.3%, and with diseases of the reproductive organs and legs — 20.7 and 22.2%. The force of influence of the indices on retirement is η2UDC=42.0***% (F=7.6) and η2FLC=40.0***% (F=13.2). Studies have revealed predicted retirement rates with UDC and FLC data.

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