Relationship between beta-lactoglobulin polymorphism and milk fatty acid composition in milk of Massese dairy ewes

The influence of milk beta-lactoglobulin phenotype on the content of fat, total protein, whey protein, casein, and fatty acids of 163 individual milk samples from Massese ewes was determined. Sampling was conducted randomly on five dairy ewe farms located in the area of origin of the Massese breed (North-West Tuscany, Italy). Three beta-lactoglobulin phenotypes were detected: their frequencies were AA 20.25%, AB 63.80% and BB 15.95%, respectively. In agreement with previous studies, parameters of milk gross composition were not significantly related with milk beta-lactoglobulin polymorphism. We demonstrate, for the first time, a significant relationship between beta-lactoglobulin phenotypes and milk fatty acid composition in ewes. The study highlighted a co-dominant effect of beta-lactoglobulin alleles on the concentration of some milk fatty acids, particularly for trans fatty acid content, that was higher in milk from heterozygous sheep. Milk from AB sheep also contained lower amount of saturated fatty acids and medium-chain fatty acids, and higher levels of long chain fatty acids.