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

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 Asp2/E Asn2, D Arg18/E Lys18 and D Val25/E Ala25 amino acid substitutions with a Mr 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.