The effectiveness of cattle selection for quantitative and qualitative traits that are of economic importance in dairy cattle breeding largely depends on the identification of the genes that control these traits, as well as their allelic polymorphism. One such gene is the gene LGB encoding the protein beta-lactoglobulin. The review provides brief information about the structure and biological role of this protein, gene polymorphism. An analysis of the literature data of various studies was carried out, which made it possible to identify and evaluate the effect of the two most common alleles of the gene LGB (A and B) on the efficiency indicators of dairy production.