The Distribution for Lof Mutations in the FANCI, APAF1, SMC2, GART and APOB Genes of the Russian Holstein Cattle Population

LoF (loss-of-function) mutations causing hereditary abnormalities and embryonic mortality are one of the reasons for a decline in fertility of cows. Currently, more than fifteen LoF mutations are known in Holsteins. In our work, we studied the frequency of LoF mutations in FANCI, APAF1, SMC2, GART and APOB genes that are associated with fertility haplotypes HH0, HH1, HH3, HH4 and HCD in Russian Holstein cattle population. We analyzed the estimated breeding values (EBVs) for daughters’ milk production and reproduction traits in sires carrying LoF mutations compared to non-carrier sires using the BLUE approach. Genotyping LoF mutations was performed by PCR, PCR-RFLP or allele-specific PCR. In total, 1521, 636, 880, 690 and 574 bulls and 896, 630, 773, 482 and 727 cows were genotyped for LoF mutations in FANCI, APAF1, SMC2, GART and APOB genes, respectively. The ratio of carriers among bulls and cows was, respectively, 2.89 and 4.13% for FANCI, 2.04 and 1.83% for APAF1, 1.14 and 2.98% for SMC2, 1.30 and 1.04% for GART, 5.57 and 2.06% for APOB. Generally, the sires carrying LoF mutations had higher EBVs for milk production traits. The greatest effect was observed for SMC2 genotype: +236 kg for 305-days milk yield, 9.0 kg for fat yield and 7.6 kg for protein yield. The bulls carrying LoF mutations in SMC2 and GART genes were characterized by the higher number semen doses per insemination (0.02-0.24 units) compared with the non-carrier bulls. The higher EBVs for the number of days open (from 12.6 (p<0.001) to 7.2 days (p<0.05) and calving interval (from 9.0 (p<0.001) to 10.5 days (p<0.01) were observed in bulls, which were carriers of LoF mutations in SMC2 and GART genes. The group of sires with the mutation in FANCI gene had the smallest length of calving interval (-6.0 days, p<0,001). Analysis of the best linear unbiased estimates showed that for insemination of offspring from bulls carriers of HH3 haplotype spent +0.026 units semen than for bulls with other mutations. The longest interval from calving to the first insemination and days open by +1.9 to 3.9 days were daughters of bulls with the GART gene (HH4). Given the dissemination of LoF mutations among the breeding sires and cows, with the aim of reducing genetically caused embryonic losses, matings of carriers bulls with mutations to cows whose fathers are hidden carriers of LoF mutations in the FANCI, APAF1, SMC2, GART and APOB gene must be excluded.