Feeding effect of yellow wine lees fermented with Candida utilis and Bacillus subtilis in the cow diet on milk composition

Yellow wine lees (YWL) are the main byproduct in the yellow wine brewing and can be used as animal feed. The deficiencies in fiber digestibility and amino acid equilibrium of YWL limited its utility value in animal feeding. The nutritional profile of YWL could be moderated after fermentation treatment. We fermented YWL with Candida utilis KF01 and Bacillus subtilis KF02, whose genomes were sequenced. We set three groups in the animal test with 15 Holstein cows: control, YWL, and fermented yellow wine lees (FYWL) group. 206 and 5 amino acid metabolism-related KEGG pathways, as well as 5257 (639 GO and 4618 eggNOG annotations) and 1579 (372 GO and 1207 eggNOG annotations) amino acid metabolism-related gene annotations were found in C. utilis KF01 and B. subtilis KF02. The collected milk samples were analyzed for composition. The contents of mono-unsaturated fatty acid (MUFA, 36.90% relative content), poly-unsaturated fatty acid (PUFA, 5.63% relative content), and essential amino acid (EAA, 2.01%) in the FYWL group milk were significantly (P < 0.05) higher. The content of flavor substances in the FYWL group (146.33 ng/mL) was the highest, followed by the control (89.19 ng/mL) and the YWL group (41.36 ng/mL). The principal component analysis (PCA) result presented the intra-group variations in flavor substances and differences in single substance among all groups. Feeding FYWL had significant effects (P < 0.05) in the Holstein cows on the milk composition.