Systematic Review of Single Nucleotide Polymorphisms of Cattle Beta-Lactoglobulin Gene and their Association with Milk Production Traits

The application of molecular genetics technology to pinpoint certain DNA markers associated with commercially significant features is highly anticipated since it has the potential to enhance the effectiveness of breeding programs by selecting young animals early for use as future breeding stock. One of the main genes expressed in bovine milk is the Beta-Lactoglobulin Gene (βLG), and its polymorphism can be used as a useful molecular marker for characteristics related to milk production. However, there is no systematic review providing information on the βLG variations in form and their relationship with characteristics of milk production in cattle. Hence, this study’s objective was to review the Single Nucleotide Polymorphisms (SNPs) of βLG and their relationship with milk production traits in cattle systematically. As stated by Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, this systematic review was carried out. Databases including Science Direct, Google Scholar, PubMed, and Web of Science were evaluated systematically using ‘polymorphisms/single nucleotide polymorphisms/genetic polymorphisms/ genetic effect/genetic variants’, ‘beta-lactoglobulin gene’, ‘Milk production traits/milk components' and 'cattle' as keywords. Articles that were identified in the electronic databases were one hundred and thirty-two (n = 132). A total of thirty-three (n = 33) studies were included in this study after screening. The findings of this systematic review indicated 11 SNPs (1810C>T, 3984A>G, 968C>A, 5239C>A, 5240A>C, 5305C>T, 301T>C, 390C>T, 435C>G, 424T>G and 422G>A) were identified with no similar SNPs identified by the reviewed articles. These findings suggest that SNPs 1810C>T, 968C>A, 5239C>A, 5240A>C, 5305C>T, 301T>C, and 390C>T are associated with some of the characteristics of milk production in cattle. This study concludes that the beta-lactoglobulin gene influences fat percentage, milk, lactose, fat, and protein yield in cattle. However, more studies need to be conducted for further validation of the identified SNPs since no articles identified the same SNPs. Furthermore, identified SNPs might be used as a potential molecular marker for the genetic enhancement of features related to milk output in cattle breeding.