GENOTYPING OF THE BETA-CASEIN A1 AND A2 VARIANTS IN CHILEAN DAIRY CATTLE

Abstract

<b>Bovine milk is a very important food for human health and nutrition. However, its consumption can also be associated with dysfunctions or pathologies in some consumers. The objective of this work was to evaluate the distribution of the -casein A1 and A2 variants in the main dairy cattle breeds used in Chile. Blood samples were obtained from 134 cattle from southern Chile, belonging to different breeds: Holstein-Friesian (HF), Jersey (JE), Montbliarde (MB), Overo Colorado (OC), and crossbreds (HYB). Genomic DNA was purified from the blood, and genotyping of the A1 and A2 variants was performed using allele-specific PCR. Genotypic and allelic frequencies were estimated by direct count, and the Hardy-Weinberg equilibrium was tested for using the chi-squared test, for a significance level of P < 0.05. Heterozygosity was evaluated by means of Wright's fixation index (FIS) using GenePop software. Genotyping of the variants showed variability in their distribution, with prevalence of A2 in almost all breeds (including HF), with the exception of OC. The 2 value indicated that the animal populations were in Hardy-Weinberg equilibrium with the exception of MB and JE (p < 0.05), with the latter showing a significant and positive FIS value suggesting inbreeding. In conclusion, our results, although preliminary, suggest that there is an opportunity to produce A2 milk in southern Chile and thus reduce the presentation of gastrointestinal dysfunctions in consumers who are affected by conventional milk.