Effects of Sea Buckthorn Polysaccharides on Rumen In Vitro Fermentation Characteristics and Microbial Composition of Hu Sheep

This study evaluated the effects of sea buckthorn polysaccharides (SBP) on rumen fermentation in Hu sheep through in vitro fermentation. A single-factor randomized design was employed with four treatment groups in which SBP was added to a basal diet at 0, 1%, 2% and 3% of the total ration dry matter (DM). Based on gas production, degradation rates, and fermentation parameters, the control group and the 2% group were selected for 16S rDNA sequencing. The results showed that compared with the control group, the 2% SBP treatment significantly increased gas production rate (<i>p</i> < 0.05). Addition of 2% and 3% SBP significantly increased DM degradability (<i>p</i> < 0.05). SBP supplementation significantly increased fermentation fluid pH (<i>p</i> < 0.05) and altered volatile fatty acid profiles, increasing the acetate/propionate ratio as well as the concentrations of butyrate, isobutyrate and valerate. Compared with the control group, the addition of 2% SBP led to significant changes in the microbial composition of the in vitro rumen fermentation fluid. It significantly increased beneficial bacterial phyla and genera, such as Bacteroidetes, <i>Rikenellaceae_RC9_gut_group</i> and others, while reducing pathogenic bacteria (<i>p</i> < 0.05). Additionally, functional prediction revealed that the SBP group was significantly enriched in pathways related to carbohydrate metabolism, biosynthesis of amino acid, and biosynthesis of secondary metabolites (<i>p</i> < 0.05). In summary, adding 2% SBP to Hu sheep feed can improve the Rumen fermentation and microbial communities. However, higher doses did not yield additional benefits in these measured indicators.