Effects of replacing peanut vine hay with wheat husk on in vitro rumen fermentation, nutrient degradability, and microbial community dynamics of buffalo

This study examined the effect of replacing peanut vine hay (PVH) with wheat husk (WH) on fermentation profiles, nutrient degradability and ruminal bacterial communities in vitro ruminal fermentation system in buffaloes. Five treatment groups (0% A, 25% B, 50% C, 75% D, 100% E), each with eight replicates, were established by replacing WH with PVH at equal graded levels, followed by anaerobic incubation at 39°C for 72 h.The results indicated that total gas production, dry matter (DM), and crude protein (CP) degradability decreased linearly with increasing WH inclusion ( P  < 0.05). Neutral detergent fibre (NDF) degradability and hydrogen production increased linearly with higher WH inclusion ( P  < 0.05). WH increased butyrate ( P  < 0.05). Alpha diversity was unchanged, while principal coordinate analysis revealed distinct clustering among treatments ( P  < 0.05). Bacteroidota (45.76–49.90%) and Firmicutes (30.91–33.72%) predominated. At the genus taxonomic level, norank_Rikenellaceae and Xylanibacter were the most abundant taxa across all treatments. Correlation analysis identified Ruminobacter and Treponema as key drivers of fermentation shifts, with strong associations with volatile fatty acid profiles and H₂ production ( P  < 0.05). Functional prediction indicated that membrane transport and signal transduction were the dominant pathways. In summary, WH is a viable alternative to PVH in buffalo diets. Despite decreasing protein degradability, it improves fibre utilisation and exerts favourable modulatory effects on the rumen microbial community, with no concomitant rise in CH₄ production.