Rumen-Protected Glucose Supplementation Enhances Yak Calf Growth Through Gut Microbiota–Metabolic Interactions

Alleviating negative energy balance in perinatal yaks is a critical challenge for safeguarding the health of both dams and calves and achieving sustainable development of yak husbandry. While RPG supplementation represents an effective nutritional strategy, its transgenerational benefits, particularly the long-term effects on offspring calf development through maternal intervention, remain largely unexplored. In the present study, low-dose RPG (150 g d−1, L-RPG, n = 6) markedly improved milk composition, elevating protein, fat, lactose, and gross energy contents (p < 0.05), and enhance calf weight gain (21.74%) with activation of the somatotropic axis (increased GH, IGF-1, etc.). Calves in this group also exhibited enhanced antioxidant capacity (higher SOD, CAT, and T-AOC) and improved immune regulation (lower IL-6, TNF-α). Multi-omics analyses revealed that L-RPG enriched beneficial taxa such as Solbacillus, Citricoccus, and Akkermansia muciniphila, optimized the hindgut microbiome, and upregulated serum metabolites including di-O-methylfraxetin and phenylalanyl-histidine. Integrated microbiota–metabolite profiling demonstrated significant cross-talk between the altered bacteria and metabolites. Collectively, supplementing dams with 150 g d−1 RPG improves milk quality, modulates the calf gut microbiota, and reshapes host metabolism, thereby synergistically promoting offspring growth. Our findings provide a comprehensive “maternal nutrition–microbiota–metabolism” framework for understanding RPG’s mode of action and furnish both theoretical insights and practical guidance for dam–calf health management in yak production systems.