Effects of adding to high concentrate diet on rumen fermentation parameters and microbial diversity of sheep.

Objective: The purpose of this study was to investigate the effects of different doses of Sophora alopecuroides (SA) on the rumen fermentation and microbial diversity of sheep.

Methods: A total of 32 healthy Dumont crossbred male lambs weighing 25.73 ± 2.17 kg were randomly assigned to 4 treatment groups with 8 replicates each: a control group (CG) fed a basal diet with a concentrate-to-forage ratio of 7:3 and three experimental groups - the 0.1% group(TG1), 0.3% group (TG2), and 0.5% group (TG3), which were fed the same basal diet but supplemented with increasing doses of SA.

Results: (1) Increasing the SA dose led to a significant linear increase (-< 0.05) in acetate, propionate, butyrate, and total volatile fatty acid (TVFA) concentrations in the rumen, as well as a significant quadratic effect (-< 0.05) on the propionate concentration. In contrast, there was a significant linear decrease (-< 0.05) in the NH-N concentration in the rumen. (2) At the level of rumen bacterial phyla, the abundance of Bacteroidetes in the rumen increased, and that of Firmicutes decreased ( = 0.08). At the genus level, the rumen abundances of Ruminococcus and Phocaeicola of sheep in the three experimental groups were significantly higher than in the control group (-< 0.05), and the abundances of Clostridiales and Candidatus-Hepatincola were significantly increased in the 0.1% and 0.3% groups ( < 0.05). (3) Regarding rumen anaerobic fungi, the differences between the control group and experimental groups at the phylum level and genus level were not significant ( > 0.05), but the relative abundances of Neocallimastigomycota and Piromyces in the 0.1% group were significantly higher than that in the control group.

Conclusion: SA addition to a high grain diet could increase the VFA concentration and pH in the sheep rumen, reduce the NH-N concentration in the rumen and improve rumen fermentation function. Although there was no significant change in rumen bacterial or fungal diversity, SA addition increased the rumen abundances of , Phocaeicola, and , decreased the rumen abundance of , and had a positive effect on the rumen microbiota to improve sheep health.