E.D. Marino, D.C.M. Fonseca*, A.N. Vasconcellos, L.M.F.S. Oliveira, A.F.M. Santos, J.C.C. Balieiro and A. M. C. Vidal
Published November 29, 2024
Genet. Mol. Res. 23 (4): gmr2348
DOI http://dx.doi.org/10.4238/gmr2348

About the Authors
E.D. Marino, D.C.M. Fonseca*, A.N. Vasconcellos, L.M.F.S. Oliveira, A.F.M. Santos, J.C.C. Balieiro and A. M. C. Vidal

Corresponding author:
D.C.M. Fonseca
E-mail: dmartinsfonseca@usp.br

ABSTRACT

This study was developed to identify possible effects of the A1 and A2 alleles of β-casein (β-CN) on the yield, composition traits, and somatic cell count (SCC) of milk from cows with the A1A1, A1A2, and A2A2 genotypes from a high-yielding Holstein herd in Brazil. Genotypic and phenotypic analyses were carried out. Genotypic analysis involved information from 1,816 Holstein cows between the years 2015 and 2019 and the characterization of allele (A1 and A2) and genotype (A1A1, A1A2, and A2A2) frequencies associated with 1,816 lactations. The different genotypes were also related to the following phenotypic traits: total milk yield; milk yield adjusted to 305 days; protein, fat, lactose, total solids, and solids-not-fat contents; and SCC. There was no difference between the genotypes for milk composition or SCC, and all genotypes showed values within the range established by Brazilian law. However, animals with the A1A1 genotype exhibited a higher 305-day lactation yield. In addition, the herd is in Hardy-Weinberg Equilibrium, indicating that these animals are responsive to genetic selection for the A2 allele.

Key words: A2 milk; β-casein; Genotype; Phenotype.