Abstract
Heat stress, particularly during the prepartum period, compromises dairy cow health and has lasting effects on offspring. This study aimed to investigate the effects of maternal yeast culture (YC) supplementation during heat stress on the intestinal health of newborn calves, with a specific focus on elucidating the associated changes in jejunal morphology, microbial community, and metabolic profiles. Cows receiving YC had lower rectal temperatures, confirming mitigated heat stress. Their calves showed enhanced immune status (higher IgA, IgG) and reduced oxidative stress and metabolic markers. Jejunal structure and barrier integrity were improved. While microbial diversity was similar, specific bacterial abundances differed (e.g., Enterococcus spp. enriched in YC calves). Metabolomic analysis revealed modulated bile acid pathways and metabolites in YC calves, correlating with the microbial shifts. In conclusion, maternal YC supplementation during heat stress supports calf early-life gut health and development through maternal-offspring programming, optimizing gut microbiota, metabolism, and immunity.