Niacin mitigates rumen epithelial damage in vivo by inhibiting rumen epithelial cell apoptosis on a high concentrate diet.

To investigate the effects of niacin on rumen fermentation, rumen epithelial antioxidant activity, and rumen epithelial cell apoptosis on high concentrate (HC) diets, nine male Hu sheep were randomly fed one of three diets: low concentrate diet (LC; concentrate: forage (C:F) = 20:80, high concentrate diet (HC; C:F = 80:20), and HCN diet (HC diet + niacin at 800 mg/kg diet air-dry matter). Compared with the LC group, the HC group had a lower rumen pH, higher volatile fatty acids and lactic acid in the rumen, reduced activity of antioxidant enzymes and total antioxidant capacity, and increased malondialdehyde content in the rumen epithelium (P < 0.05). Rumen epithelial papilla morphology was decreased, and apoptosis-related indicators and serum inflammatory cytokines were increased in the HC group over the LC group (P < 0.05). Compared with the HC diet, the HCN diet increased rumen pH, rumen epithelium antioxidant capacity, and rumen epithelial papilla morphology, decreased rumen lactate content, serum inflammatory cytokines, and apoptosis-related indicators (P < 0.05). Therefore, adding 800 mg/kg niacin helped protect against rumen epithelial damage by avoiding drastic changes in the rumen environment and improved rumen epithelial antioxidant capacity to inhibit rumen epithelial cell apoptosis in sheep on a HC diet.