Identification of lethal recessive genetic variants in Holstein cattle

Abstract

Artificial insemination is the main method of herd reproduction in cattle breeding and is associated with the risk of spreading genetically determined diseases. Widely used high-yield bulls are often carriers of fertility haplotypes and other harmful genetic variants. The traditional approach to identifying genetic factors associated with lethal recessive variants that cause defects or death is to track the common ancestors of sick animals using pedigrees and is unable to detect harmful genetic variants that cause the death of embryos. A homozygous harmful phenotype leads to early death of the developing embryo, the only observed consequence of this is lower fertility of the parents. With the development of genomic technologies, it has become possible to identify mutations that lead to embryonic death at different stages of fetal development. The purpose of the work was to perform an analytical review of the literature on the identification of lethal recessive genetic variants in cattle. The haplotypic approach is considered as the main method of detecting harmful mutations. The essence of the method is to search for segments in the genome, the actual homozygosity of which tends to zero, unlike the expected one. Haplotype analysis revealed lethal recessive genetic variants and causal mutations in Holstein cattle, common in populations with a frequency of 0.07-47.75%. Considering the occurrence of lethal genetic variants in cattle populations, the disclosure of the basis of genetically determined diseases will make it possible to screen animals and eliminate carriers from the breeding process.