Genetic Polymorphism of β-Lactoglobulin in Native Sheep from the Island of Pag
Vlatka Cubric-Curik1*, Maria Feligini2, Jasmina Lukac-Havranek1, Ino Curik3 and Giuseppe Enne2,4
1Dairy Science Department, Faculty of Agriculture, University of Zagreb, Svetošimunska 25, HR-10 000 Zagreb, Croatia
2Istituto Sperimentale Italiano »Lazzaro Spallanzani«, Via Capolago 16, I-20133 Milan, Italy
3Animal Science Department, Faculty of Agriculture, University of Zagreb, Svetošimunska 25, HR-10 000 Zagreb, Croatia
4Dipartimento di Scienze Zootecniche, Università di Sassari, Via De Nicola, I-07100 Sassari, Italy
Article history:
Received: July 6, 2001
Accepted: November 8, 2001
Key words:
β-lactoglobulin polymorphism, Pag sheep, Pag cheese
Summary:
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.
*Corresponding author: 
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