GENETIC POLIMORPHISM OF BETA-LACTOGLOBULIN IN COW'S MILK OF HOLSTEIN AND TROPICAL MILKING CRIOLLO

摘要

The genetic variants (A and B) of the beta-lactoglobulin in cow's milk has been associated with important technological properties in dairy processing. The objectives of this study were to determine the genetic variants and to estimate the phenotypicfrequencies of beta-lactoglobulin (beta-LG) in cow's milk of Holstein and Tropical Milking Criollo (TMC), as well as to evaluate the effect of the phenotypes on the total concentration of beta-LG. The phenotype was determined in 382 milk samples of Holstein and 64 of TMC. The genetic variants identified by capillary electrophoresis in free zone were A and B, with genotypes AA, AB and BB. The genotypic frequencies (0.14, 0.33 and 0.53 in TMC; 0.19, 0.57 and 0.24 in Holstein) were compared using the Chi-squared test (X~2) and were different (p<=0.01) in the two breeds. The total concentration of beta-LG in milk was higher (p<=0.05) when the allele A was present. The total concentration of beta-LG according to the phenotype followed the order AB > AA > BBfor both breeds; these differences were significant in TMC cows. The analysis of the results suggests that the physical-chemical and technological characteristics of TMC cow's milk could be different from those of the Holstein cows.