The aim of our study was to analyze the reproduction dynamics and fertility rates of the Ayrshire cattle population in Russia and to assess the level of influence of the AH1 haplotype on the incidence of stillbirth. For an overall fertility estimate, we used 390,769 records of 67 dairy herds in Russia from 2003 to 2018. Against the background of stable population growth, the average stillbirth rate was 3.33% and the abortion rate was 0.075%. A high percentage of stillbirth (5.13%) from heifers the first fertilization event, and there was a high rate of abortions in older cows (11 calving, 1.76%). An analysis of 62,534 records of bulls with the rs475678587C>T variant of UBE3B gene (AH1 haplotype) (n = 69, of which 51 bulls were free from and 18 were carriers of AH1) for the period 2002 to 2018 showed that the proportion of female offspring of AH1-C bulls completing at least one full period of lactation was about one-third of the total livestock. An analysis of the results of mating with AH-F and AH-C bulls for the broodstock as a whole (without taking into account the female genotype) did not reveal significant differences in the number of stillbirths and abortions. Linear regression analysis showed that the status of AH1 bulls did not significantly affect stillbirth rates. An analysis of the results of calving and the reproductive ability of the offspring of AH-C bulls showed an increase in the frequency of stillbirths, confirmed by the results of linear regression analysis, which revealed a significant effect of bull fathers carrying AH1on the proportion of stillbirths experienced by their daughters. Our studies confirm that the rs475678587C>T variant of the UBE3B gene (haplotype AH1) has a significant effect on the rate of stillbirth of a cow or heifer if their father is a carrier of this genetic defect.
Relevance. In conditions of intensive dairy cattle breeding, the incidence of cows with mastitis continues to be an urgent problem. The number of somatic cells (CCCs) in milk is a breeding indicator for improving the health of the mammary gland of cows. The study of animal resistance to the disease, which is based, among other things, on the genetic component, will make it possible to increase the efficiency of breeding in the future. The purpose of this work is a comparative analysis of the relationship of polymorphic variants of the ACS L1 (rs208522533) and CD62L (rs41803917 and rs41803917) genes with indicators of milk productivity and the level of somatic cells in the milk of Ayrshire cows.Methods. A sample of first-calf cows of Ayrshire breed (n = 191) belonging to one of the breeding farms of the Leningrad region was formed. Animal genotypes were determined by PCR-PDRF. Analysis of the genotype frequency by rs208522533 of the ACS LI gene showed that 99% of the animals were carriers of the GG genotype.Results. The results of studies of the CD62L gene showed that rs41803917 determined a high frequency of the G allele (80.4%) and on average more than 60% of animals had the GG genotype. rs109966956 of the CD62L gene revealed a high frequency of the C allele (80.1%) and 64.9% of the animals had the CC genotype. High values of BOX PC were established in small groups of animals with the AA genotype according to rs41803917 (p £ 0.05) and the TT genotype according to rs109966956 (p £ 0.001). Individuals with the AG genotype according to rs41803917 of the CD62L gene had high protein percentages (p £ 0.05) and low BSC (p £ 0.05). The results obtained indicate that SNPs rs41803917 and rs41803917 of the CD62L gene can be considered as potential markers of resistance to mastitis in Ayrshire cows.
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