β-Lactoglobulin genetic variants in Brown Swiss breed and its association with compositional properties and rennet clotting time of milk

beta-Lactoglobulin (beta-Lg) polymorphism of Holstein Friesian and Brown Swiss breeds were studied by applying native polyacrylamide gel electrophoresis. In addition, total solids, protein, fat ash, lactose and solid non-fat contents, rennet clotting time and major minerals (potassium, calcium, phosphorus and magnesium) of milk from Brown Swiss breed were examined. Phenotype and allele frequencies of beta-Lg in both breeds were estimated and the association of the beta-Lg genetic variants with the examined properties of Brown Swiss milk was studied. As a result of the study, beta-Lg AA, AB and BB phenotypes were found in both Holstein Friesian and Brown Swiss breeds. The gene frequencies of beta-Lg A and B were 0.27 and 0.73 in Holstein Friesian and 0.44 and 0.56 in Brown Swiss breeds, respectively. Therefore, beta-Lg B allele gene was found more common in both breeds. In addition, significant differences were observed in beta-Lg genotypes between two breeds. Also, significant relationships were found between beta-Lg genetic variants and total solids (p < 0.05), fat (p < 0.01), calcium (p < 0.05) and phosphorus (p < 0.05), while no relationship was obtained for the other parameters studied in the milk of Brown Swiss breed. (C) 2003 Elsevier Science Ltd. All rights reserved.