Occurrence of qualitative and quantitative polymorphism at donkey beta-Lactoglobulin II locus

Abstract With the use of a proteomic approach a genetic screening of 70 individual donkey milk samples, from two autochthonous breeds reared in Italy, was carried out to determine the genetic polymorphism at donkey β-Lgs loci . The achieved results showed the occurrence of the new β-Lg II E genetic variant, differing from β-Lg II D reference for D Asp 2 /E Asn 2 , D Arg 18 /E Lys 18 and D Val 25 /E Ala 25 amino acid substitutions with a M r 18 256 Da. Moreover a quantitative polymorphism seemed to affect the donkey β-Lg II locus since four phenotypes, with a relative quantitative percentage respect to total whey protein ranging from 0% to 3.65%, were detected by HPLC analysis.