М. И. Селионова Most sheep breeds are low-prolific, which, along with other reasons, leads to low profitability of the industry. In intensive systems of industrial sheep breeding, high prolificacy of sheep can increase the efficiency of sheep production. Cross-breeding of low-prolific breeds with high-prolific breeds has been the main means of genetic improvement of prolificacy, while intra-breed selection has been considered relatively ineffective due to low heritability of the trait. Mutations that reliably affect ovulation rate and hence lamb numbers have been found in several breeds around the world in genes designated as “major genes”. Most of these mutations are mapped in genes related to the TGFβ superfamily. Genotyping for these major genes permits the use of a marker-assisted selection method for crossbreeding to introduce useful mutations into new breeds. Mitochondrial DNA analysis, whole genome association studies (GWAS), whole genome sequencing, transcriptome analysis and proteomic studies of high- and low-prolific sheep have identified additional genetic variations with moderate or minor effects on prolificacy. Using information on polymorphisms in these “medium genes” and “minor genes” may facilitate selection work for higher prolificacy within a particular production system. Although high prolificacy is associated with a risk of pregnancy toxicosis, increased embryonic mortality, reduced lamb survival in early postnatal ontogeny, and a high risk of shortening the productive longevity of sheep, the prospect is to identify a set of genes with moderate effects on prolificacy.
Научная статья 
генная интрогрессия