Graded selenium supplementation restructures yak colostrum composition and metabolomic organization under high-altitude conditions.

Selenium (Se) plays crucial roles in redox regulation and metabolic homeostasis, yet its effects on yak colostrum remain poorly understood. This study evaluated graded dietary Se supplementation during the periparturient period on colostrum composition, maternal physiological status, and metabolomic profiles in high-altitude yaks. Thirty pregnant yaks received 0, 0.3, or 0.6 mg Se/kg dry matter. Among animals with normal placental expulsion (n = 6/group), high Se supplementation increased milk fat, protein, lactose, solids-not-fat, and immunoglobulin concentrations. Untargeted metabolomics detected 1629 metabolites and revealed dose-dependent remodeling, particularly in lipid-, amino acid-, and energy-related pathways. Se supplementation was associated with reduced oxidative stress and enhanced endocrine indicators of lactational adaptation. Integrative analyses linked Se-responsive metabolite modules with maternal physiological traits and milk fat globule membrane proteins. Collectively, these findings indicate that maternal Se supplementation was associated with coordinated remodeling of yak colostrum composition and metabolic organization under high-altitude conditions.