Effects of fermented herbal tea residues on the intestinal microbiota characteristics of Holstein heifers under heat stress

Herbal tea residue is a reusable resource with high nutritional value and bioactive substances content, which can be used as a feed additive. In the present study Herbal tea residues were mixed with oat hay, corn flour, and molasses, and fermented by lactic acid bacteria, and then fed to Holstein heifers. Fermented Herbal tea residues supplementation improved physiological indices of respiratory frequency and rectal temperature. Fermented Herbal tea residues significantly reduced the concentrations of heat stress-related parameters, immunoglobulins, serum hormones, and antioxidant capacity-related parameters. The heifers body height increased considerably, while their energy metabolism rates were stimulated in response to fermented HTR. Moreover, fermented Herbal tea residues significantly increased the levels volatile fatty acids in the rectal contents. We studied the fecal microbial community composition of 24 Holstein heifers. The fermented Herbal tea residues may improve growth traits and energy utilization efficiency, increased antioxidant capacity, enhance immunity, and relieve heat stress by changing microbial communities.