Associations of bovine beta-casein and kappa-casein genotypes with the genomic merit in Holstein-Friesian cattle

Abstract

Abstract The relationship between index values used in evaluating the genomic value and essential markers such as casein genes provides important information at the herd level. Therefore, this study aimed to determine the association between casein gene genotypes and the indices of genetic merit in Holstein-Friesians. A total of 805 cows were genotyped using the Affymetrix® Axiom® array system. We used the data composed of TPI and NM values as well as PTA indices, including milk, fat, %fat, protein, %protein, CFP, PL, SCS, DPR, LV, and UDC of each animal. The statistical analysis consisted of the one-way ANOVA test followed by Tukey's test. The A2A2 and the AB genotypes were predominant in the CSN2 and CSN3 genes, respectively. The A2A2 animals have higher TPI and NM values. Moreover, they exhibited higher PTA values for protein, CFP, and PL. On the other hand, the A1A1 genotype was significantly associated with the highest UDC. Concerning the CSN3 haplotypes, the BB animals had higher PTA-%protein and -PL than alternative haplotypes. The AA and AB haplotypes were significantly associated with the highest SCS and DPR values, respectively. In addition, the BE haplotype had the highest NM. Selection procedures focusing on casein genes in dairy cattle are becoming increasingly common worldwide, especially for A2 milk. However, herd-based dynamics are also fundamental to providing a desired genetic merit for the animals. This study may be valuable for further analyses regarding the selection decisions through the breeding values of the candidates in commercial dairy herds.