Evidence for a third allele at the beta-lactoglobulin (beta-Lg) locus of sheep milk and its occurrence in different breeds.

Milk samples from 189 Merinoland Sheep, 145 Black Faced Mutton Sheep, 89 East Friesian Milk Sheep, 36 Rhön, 36 Pleven, 23 Tsigaja, 25 Black Razka and 86 Hungarian Merino X Pleven (F1) sheep were analysed by polyacrylamide gel electrophoresis under acid conditions and isoelectric focusing in ultrathin layer polyacrylamide gels with carrier ampholytes. Six different beta-lactoglobulin (beta-Lg) phenotypes (A, AB, B, AC, BC and C) were observed by both methods. The occurrence of three codominant alleles (beta-LgA, beta-LgB, beta-LgC) at an autosomal locus (beta-Lg) was supported by family and population data on genetic equilibrium. Differences in gene frequencies between the breeds were observed.