Modern dairy farming is characterised by high selection intensity and the use of a limited number of bulls-producers. This increases the likelihood of widespread genetic defects in livestock populations. Genome-wide studies have identified DNA loci associated with the disruption of foetal embryonic development and its death, which have been called “fertility haplotypes”. The aim of this study is to analyse the occurrence of АН1 haplotype or rs475678587 in Ayrshire bulls (n = 186) used in the artificial insemination system of Russia and to evaluate the reproductive and productive qualities of their daughters. The proportion of genetic defect carrier bulls in the analysed sample cohort was 16.66%. Analysis of the proportion of carriers of unwanted haplotype depending on the place of birth of the bull for service showed that the highest frequency was observed in bulls of Canadian origin (26.66%). Based on data on 97 478 cow and heifer calvings, stillbirth and abortion rates were analysed and cow reproduction rates were based on an AH1 status for the bull-father and bull for service. We observed a significant increase (P < 0.05 and P < 0.001) in the incidence of stillbirths when crossing the daughters of AH1-C bulls with AH1-C bulls. There was no negative association of abortion rates and reproductive qualities with AH1 haplotype. The high incidence of AH1 haplotype among animals of Ayrshire breed requires regular screening for the carriers of this haplotype not only among bulls, but also in cows.

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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).