Yeast culture in weaned lamb feed: a proteomic journey into enhanced rumen health and growth.

BACKGROUND: Using yeast culture as additives in ruminant feed prevents rumen microbial dysbiosis, enhances performance, and regulates rumen pH. The yeast culture used in this study was developed in-house, and has been shown to promote rumen epithelial growth in several sheep trials. Changes in protein expression associated with the promotion of rumen epithelial development following the addition of yeast culture, along with the associated molecular mechanisms, remain unknown. We used 20 45-day-old weaned lambs to investigate the specific proteins and molecular mechanisms involved in these processes. Half of the lambs were fed yeast culture, and the other half were used as controls. RESULTS: Yeast culture enhanced growth performance, facilitated rumen fermentation, and promoted rumen papilla development in weaned lambs. Proteomics data identified 4,831 proteins in the rumen epithelial tissue of lambs, comprising 87 upregulated and 425 downregulated proteins. Administration of yeast culture activated multiple molecular functions within rumen epithelial cells, including oxidative phosphorylation, glutathione metabolism, apoptosis, cell cycle, and vitamin digestion and absorption. The expression of proteins associated with cell cycle regulation increased, whereas those associated with apoptosis decreased. Administration of yeast culture also reduced the duration of the G(0)/G(1) phase of rumen epithelial cells and accelerated the cell cycle. Furthermore, yeast culture showed increased cyclin D1, cyclin-dependent kinase (CDK)2, CDK4, CDK6, and cyclin E1 expressions and decreased cytochrome C (Cyto-c), Bcl-2-related X protein (Bax), cleaved caspase 3 (C-caspase 3), caspase 3, and cleaved caspase 7 (C-caspase 7) protein expressions. Yeast culture upregulated the insulin-like growth factor-1 receptor (IGF-1R) and insulin-like growth factor-binding protein 5 (IGFBP-5) mRNA expressions in rumen epithelial cells. CONCLUSIONS: Yeast culture facilitates rumen epithelial development by regulating the cell cycle and IGF-1 signaling and reducing the expression of proteins associated with apoptosis in rumen epithelial cells. The findings of this study provide novel insights into the molecular mechanisms through which yeast culture promotes rumen epithelial development in weaned lambs.