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 divided into: 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, increased 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 in ammatory 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 in ammatory 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.

Background: Creatine pyruvate (CrPyr) is a new multifunctional nutrient that can provide both pyruvate and creatine. It has been shown to relieve the heat stress of beef cattle by improving antioxidant activity and rumen microbial protein synthesis, but the mechanism of CrPyr influencing rumen fermentation remains unclear. This study aimed to combine 16S rDNA sequencing and metaproteomics technologies to investigate the microbial composition and function in rumen fluid samples taken from heat-stressed beef cattle treated with or without 60 g/d CrPyr. Results: 16S rDNA sequencing revealed that there was no significant differences in the α-diversity indices between the two groups. By analyzing the expression profiles of 700 distinct proteins, we found that CrPyr administration increased the fatty acid β-oxidation, promoted the interconversion from pyruvate to phosphoenolpyruvate, acetyl-CoA and malate, up-regulated gluconeogenesis and citrate cycle metabolism, and promoted the biosynthesis of amino acids. Conclusions: The increased generation of ATP during fatty acid β-oxidation or citrate cycle and the up-regulation synthesis of microbial protein in rumen of beef cattle treated with CrPyr, may help decreased oxidative stress, regulate energy metabolism, and further improve the rumen fermentation characteristic under heat stress.