Association between Fertility HCD Haplotype, Milk Production, and Reproductive Performance in Holstein Cows

The survey results of testing the Holstein cows for carriage of the fertility haplotype for cholesterol deficiency (HCD) associated with the fetal death detected at various stages of prenatal and early postnatal ontogenesis has been reported. Economically important traits of the animals tested as carrying the defect caused by HCD in their genotypes are examined. The survey sample consisted of the animals (n = 583) born in 2007–2017 on the breeding farm in Leningrad oblast. A comparative assessment of the HCD⁺-affected animals (tested carriers of a genetic defect caused by cholesterol deficiency) and the HCD–-unaffected animals (tested noncarriers of a genetic defect caused by cholesterol deficiency) was performed based on their milk production and reproductive performance parameters. DNA extracted from animal blood served as the testing material. The genotypes were determined based on the polymerase chain reaction with the use of allele-specific primers. It was found that 35 animals (6.0%) had a mutant allele at the ApoB gene locus present in their genotypes. These cows were not inferior to their genetic defect-free peers in breeding value for milk yields and milk protein and fat percentage. The HCD⁺-affected cows born in 2014 were characterized by higher values for the milk protein content (3.29 ± 0.05%) when compared to the HCD–-unaffected cows (3.17 ± 0.01%). A smaller number of sperm doses were used to reach effective insemination in the HCD carrier cows born in 2013 (n = 11) and 2014 (n = 11), which significantly affected the terms of the first effective-insemination. The cows born in 2014 carrying a mutant allele at the ApoB gene locus present in their genotypes had less service interval length when compared to their peers. The HCD⁺-affected cows used in production have no impact on overall herd performance and fertility. However, the animals with the HCD⁺ status should be identified and registered in a timely manner. The record-keeping system can allow us to reduce the number of carriers of this genetic defect in subsequent generations.