Herbal formula alleviates heat stress by improving physiological and biochemical attributes and modulating the rumen microbiome in dairy cows

Heat stress significantly impacts dairy cow productivity, health, and welfare. This study evaluated a self-developed herbal formula as a dietary intervention to mitigate heat stress. A total of 198 lactating cows were divided into two groups: a Control group receiving standard total mixed rations and a Herbs group supplemented with herbal formula for 60 days. Various parameters were assessed, including milk yield and composition, antioxidant capacity, immune responses, stress-related gene expression, and rumen microbial composition. Compared to the Control group, cows in the Herbs group showed improved feed intake, milk yield and quality, rumination frequency, and enhanced antioxidant activity and immune response. Rumen microbiome analysis revealed a reduced relative abundance of Proteobacteria and <i>Ochrobactrum</i> in the Herbs group, along with an enrichment of beneficial genera such as <i>Lachnospira</i>. Functional predictions indicated that the Herbs group exhibited enhanced glycolysis/gluconeogenesis, pyruvate metabolism, and starch and sucrose metabolism, reflecting improved fermentation efficiency and energy utilization. In conclusion, the herbal formula improved physiological and biochemical attributes, boosted antioxidant and immune responses, and modulated the rumen microbiome, contributing to the alleviation of heat stress in dairy cows. These findings highlight its potential as a natural dietary strategy to support dairy cow health and productivity under heat stress conditions.