GENETIC-POLYMORPHISM OF BOVINE-MILK PROTEINS IN HOLSTEIN-FRIESIAN ANDFLECKVIEH BREEDS EXPLOITED IN SPAIN

Genetic variants of bovine milk proteins alpha(s1)-, alpha(s2)-, beta- , kappa-casein (-CN), and beta-lactoglobulin (beta-LG), were studied b y isoelectric focusing using PhastSystem in milk samples of 429 Holste in-Friesian, and 174 Fleckvieh (German Simmental) breeds exploited in Spain. Genotype frequencies and allele frequencies were estimated. Var iant alpha(s1)-CNA was present in the Holstein-Friesian, and was absen t in Fleckvieh breed, while the variants beta-CN C, alpha(s2)-CN D, an d kappa-CN C were only found in Fleckvieh breed. Significant differenc es in allele frequencies between the 2 breeds were observed at the alp ha(s1)-, beta- and kappa-CN loci. Only the frequencies of the alpha(s2 )-CN, and beta-LG variants did not differ. The most common casein hapl otypes were BA(2)A (alpha(s1)-, beta- and kappa-CN respectively) in th e 2 breeds studied. These results were compared with those obtained in Holstein-Friesian and Fleckvieh breeds from the literature.