Effects of Sea Buckthorn Flavonoids on Growth Performance, Blood Biochemical Indexes, Rumen Fermentation and Rumen Bacteria of Hu Sheep Fed with High-Concentrate Diet
Simple Summary High-concentrate diets are widely used to improve growth efficiency in intensive sheep production, but prolonged feeding may adversely affect rumen fermentation and animal health. Sea buckthorn flavonoids are plant-derived bioactive compounds with potential antioxidant and immunomodulatory effects. In this study, 30 6-month-old fattening male Hu sheep were randomly assigned to a high-concentrate diet group (no supplement or 0.30% sea buckthorn flavonoids) for 45 days. Supplementation increased average daily gain and improved feed conversion without affecting feed intake. It also increased serum total antioxidant capacity and several immune-related indicators, increased ruminal acetate and valerate concentrations, and altered the relative abundance of specific rumen bacterial genera. Total volatile fatty acid concentration showed an increasing tendency, whereas rumen pH remained unchanged. Serum alanine aminotransferase activity also increased, and its biological significance requires further investigation. These findings suggest that sea buckthorn flavonoids may improve growth efficiency and selected physiological and ruminal responses in Hu sheep fed a high-concentrate diet. Further dose–response studies are needed to determine the optimal supplementation level.