Effects of BLG polymorphism and dietary supplementation with carob pulp on ewe milk traits and fatty acid composition

Abstract

The current study examined the effect on milk traits and composition of the replacement of barley grain with carob pulp as a supplement for grazing ewes with different genotypes at the β-lactoglobulin (BLG) locus. Forty-six Valle del Belìce lactating ewes were chosen for the feeding trial and split into control and carob groups based on the BLG p.Tyr38His polymorphism. The carob group received a supplement of 250 g/d of carob pulp, whereas the control group received 250 g/g of a barley whole grain-based concentrate. There were no milk yield or gross composition variations related to the BLG genotype. Nevertheless, milk fatty acid composition was influenced by the BLG polymorphism. Compared to the AB genotype, milk from BB sheep had higher concentrations of linoleic, linolenic acids, and total polyunsaturated fatty acids. The addition of carob pulp did not significantly modify fat and protein-corrected milk, whereas reduced protein and urea concentration, increased the fat content but worsened the milk quality in terms of fatty acid composition, increasing saturated and medium chain fatty acids. The genotype × feed interaction had no appreciable effect on milk composition or quality. HIGHLIGHTS Diet, genotype, and their interaction affect the milk traits and quality. Carob pulp reduced protein, urea and worsened fat quality. The genotype positively influenced the milk fat quality.