Genetic variability and population structure in loci related to milk production traits in native Argentine Creole and commercial Argentine Holstein cattle

Many cattle breeds have been subjected to high selection pressure for produ ction traits. Consequently, population genetic structure and allelic distri bution could differ in breeds under high selection pressure compared to uns elected breeds. Analysis of kappa-casein, alpha(SI)-casein and prolactin ge ne frequencies was made for Argentine Creole (AC) and Argentine Holstein (A H) cattle herds. The calculated F-ST values measured the degree of genetic differentiation of subpopulations, depending on the variances of gene frequ encies. The AC breed had considerably more variation among herds at the alp ha(S1)-casein and kappa-casein loci. Conservation strategies should conside r the entire AC population in order to maintain the genetic variability fou nd in this native breed.