Genetic Polymorphism of β-Lactoglobulin in Native Sheep from the Island of Pag

Abstract

Milk samples from 248 Pag ewes, belonging to 14 different flocks and located through the Pag Island (Croatia), were analyzed by isoelectrofocusing and PCR-RFLP. Two genetic variants (A and B) and three genotypes (AA, AB and BB) of β-lactoglobulin have been identified. According to the allele frequency (A=0.48, B=0.52) and occurrence of genetic variants, the Pag breed is similar to other Mediterranean dairy sheep breeds. The observed genotype frequencies at the β-lactoglobulin locus (AA=0.185, AB=0.589 and BB=0.226) were significantly different from those expected from Hardy-Weinberg equilibrium. In comparison with 12 different studies related to Mediterranean dairy sheep populations, the significant departure from Hardy-Weinberg was also obtained in Valle del Belice sheep. However, the sample size required for detection of the same amount of departure from the Hardy-Weinberg as it was observed in Pag sheep was only sufficient in four studies (including Pag sheep). The superiority of the AB β-lactoglobulin genotype for milk production could be one of possible reasons for the observed excess of heterozygotes and allele frequencies at intermediate level.

Keywords

• β-lactoglobulin polymorphism
• Pag sheep
• Pag cheese