Genetic polymorphism of milk protein loci in Argentinian Holstein cattle

Some alleles of milk protein loci are associated with superior cheese production characteristics. The genetic polymorphism of the milk protein loci alpha (s1)-casein, beta -casein, kappa -cascin and beta -lactoglobutin was examined in Argentinian Holstein cattle. Samples from 12 herds of four regions of Cordoba were analyzed by starch gel electrophoresis. The chi (2) test was used to assess whether the populations were in Hardy-Weinberg equilibrium. Genotypic diversity was analyzed by the Shannon-Weaver index. The observed genotypic frequencies were analyzed by Hedrick's genetic identity and the genetic distance of Balakrishnan and Sanghvi. The allelic and genotypic frequencies were similar to those of other Holstein populations. The genotypic frequencies of the alpha (s1)-casein and beta -casein loci were in equilibrium, whereas in some populations the kappa -casein and beta -lactoglobulin loci were not. According to the Shannon-Weaver index the total genetic diversity within each herd was greater than 96%. The high values of identity agreed with the low genetic distances among populations. We conclude that there is extensive genetic homogeneity in Holstein cattle in Cordoba Province and that it would be feasible to select for B alleles at the kappa -casein and beta -lactoglobulin loci in order to improve the quality of milk available for cheese manufacturing.