Impacts of trehalose supplementation on ruminal microbiota and productivity of Japanese Black heifers under heat-stressed conditions.

Objective: Hot environments negatively affect cattle productivity, and global warming also causes heat stress, thereby adversely impacting cattle production. Improving cattle management under such conditions is an urgent issue. Trehalose can ameliorate volatile fatty acid production and the diversity of ruminal microbiota in dairy cattle. However, no studies have evaluated on Japanese beef heifers. In this study, we investigated the effects of trehalose supplementation on the ruminal microbiota and productivity of Japanese Black heifers under heat-stressed conditions.

Methods: Six cyclic Japanese Black heifers were divided into two groups: control and trehalose supplemented. The ruminal microbiota, pH, and volatile fatty acid production of these heifers were analyzed over 10 weeks in the summer in central Japan.

Results: During the experimental period, the heifers in the control group showed significantly higher concentrations of ruminal acetic and propionic acids than those in the trehalose-supplemented group (p<0.05, two-way repeated measures ANOVA). The acetic/propionic acid ratio showed no significant difference between the two groups. The alpha diversity in the ruminal bacterial biota in the trehalose supplemented group was higher than that in the control group (p<0.05, two-way repeated measures ANOVA) along with a change in the beta diversity of the ruminal fungal biota (p<0.05, PERMANOVA). LEfSe analysis in ruminal microbiota identified specific microorganisms in the control and the trehalose-supplemented samples: 4 and 13 in bacteria; each one fungus; 5 and 4 protozoan families, respectively.

Conclusion: Trehalose supplementation in the summer improved ruminal microbiota, especially the types of ruminal bacteria and fungi related to carbohydrate digestion, and maintained the balance of ruminal VFA production in Japanese Black heifers. Therefore, trehalose supplementation in feed could improve cattle production under heat-stressed conditions and in global-warming scenarios.