Abstract
Some alleles of milk protein loci are associated with superior cheese production characteristics. The genetic polymorphism of the milk protein loci alphas1-casein, beta-casein, k-casein and beta-lactoglobulin was examined in Argentinian Holstein cattle. Samples from 12 herds of four regions of Córdoba were analyzed by starch gel electrophoresis. The chi² 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 alphas1-casein and beta-casein loci were in equilibrium, whereas in some populations the k-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 Córdoba Province and that it would be feasible to select for B alleles at the k-casein and b-lactoglobulin loci in order to improve the quality of milk available for cheese manufacturing.
Highlights
The milk proteins αs1-casein, β-casein, κ-casein and β-lactoglobulin are determined by the loci CASA1, CASB, CASK and LGB, respectively
Allele B predominates in European breeds, whereas allele C is frequent in zebu breeds, but absent in Holsteins
The C variant of the αs1-casein locus is found in some European breeds but not in Holsteins (Aschaffenburg and Drewry, 1955; Li and Gaunt, 1972)
Summary
The milk proteins αs1-casein, β-casein, κ-casein and β-lactoglobulin are determined by the loci CASA1, CASB, CASK and LGB, respectively. Our objetive was to analyze the genetic polymorphism and the genetic variability distribution of milk protein loci in Holstein cattle of Córdoba Province, Argentina. The allelic and genotypic frequencies in Argentinian Holstein cattle from Córdoba were similar to those for other studies of this breed in other countries (Aschaffenburg and Drewry, 1955; Li and Gaunt, 1972; Ng-Kwai-Hang et al, 1984; Poli and Antonini, 1991; Van Eenennaam and Medrano, 1991).
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