Effects of betaine on ileal tissue and intestinal microbial metabolism in Tibetan sheep

Research on betaine's role in Tibetan sheep ileal development and the microbiota-metabolite axis remains scarce, and the mechanism by which it enhances intestinal health through its function as a methyl donor has not yet been elucidated. This study evaluated the effects of 0.08% dietary betaine supplementation on 60 weaned male Tibetan lambs (2 months old, with a mean body weight of 17.72 ± 0.19 kg), which were randomly divided into a control group (Ctrl) and a betaine group (Bet), with 30 lambs in each group. After a 10-day adaptation period followed by a 90-day formal feeding period, 6 lambs from each group were randomly selected for slaughter. Results showed that betaine supplementation significantly increased ileal villus height and the villus height-to-crypt depth (VH/CD) ratio ( P  < 0.05), enhanced total antioxidant capacity (T-AOC), reduced levels of malondialdehyde (MDA), lipopolysaccharide (LPS), and tumor necrosis factor-α (TNF-α) in the ileum, and increased Claudin-1 levels ( P  < 0.05). It also raised total short-chain fatty acids (SCFAs), acetate, and propionate concentrations in the ileum, along with the relative abundance of Bifidobacterium and Aeriscardovia ( P  < 0.05), and influenced arginine and proline metabolism as well as glycerophospholipid metabolism to enhance antioxidant and immune functions. 0.08% betaine can regulate ileal SCFA concentrations by modulating microbial composition and metabolic pathways, thereby supporting jejunal barrier function, providing a theoretical basis for its application as a functional feed additive.