Yeast-fermented feed improves growth and meat quality in meat duck: Integrated metabolomics and proteomics reveal amino acid metabolic mechanisms.

Fermented feed is increasingly used in monogastric animal production to support growth, but little is known about its effects on meat quality or the mechanisms drive these effects. We fed 240 one-day-old Cherry Valley ducks either a basal diet or the same diet supplemented with 5% yeast-fermented feed for 42 days. Growth performance and carcass traits were recorded at slaughter, Breast muscle was analyzed for quality, chemical properties, amino acid composition, and subjected to metabolomics and proteomics. Results showed that ducks fed yeast-fermented feed had higher body weight at 42-d-old (p = 0.042), higher body weight gain from 15-d-old to 42-d-old (p = 0.036), and lower feed to gain ratio from 15-d-old to 42-d-old (p = 0.032) and the whole experiment period (p = 0.046) compared with the control group. Additionally, ducks fed yeast-fermented feed had higher semi-eviscerated yield (p = 0.001) and eviscerated yield (p = 0.001) compared with control group. Moreover, breast muscle from ducks fed yeast-fermented feed contained less crude fat (p = 0.023) but more phenylalanine (p = 0.004) and lysine (p = 0.038) than the control group. Omics analysis identified 179 differentially abundant metabolites and 388 differentially expressed proteins, converging on three amino acid-related pathways including glycine, serine and threonine metabolism, arginine and proline metabolism, and aminoacyl-tRNA biosynthesis. Notably, glycocyamine, sarcosine, creatine, creatinine, glycine amidinotransferase (GATM), guanidinoacetate N-methyltransferase (GAMT), and creatine kinase U-type, mitochondrial (Ckmt1) were up-regulated in duck breast muscle by dietary supplement of yeast-fermented feed. Correlation analysis revealed 24 significant associations among key molecules, and multiple metabolites and proteins correlated with meat quality traits including crude fat content, phenylalanine, and lysine. In conclusion, dietary supplement of 5% yeast-fermented feed improves meat duck growth performance during the late phase and decreased feed to gain ratio for the whole experimental period, enhanced carcass yields and reduced breast muscle crude fat while increasing phenylalanine and lysine. Multi-omics integration revealed glycine, serine and threonine metabolism and arginine and proline metabolism as central regulatory pathways, with creatine biosynthesis enzymes and metabolites identified as key biomarkers. These findings provide a mechanistic basis for using yeast-fermented feed to enhance duck meat quality.