Dietary Ophiopogon japonicus Fibrous Root Byproduct Enhances In Vitro Rumen Fermentation, Antioxidant Status, and Microbiota in Yaks

The tuberous roots of Ophiopogon japonicus are well-known Chinese traditional herbal medicine. However, as a byproduct, the fibrous roots of O. japonicus (FROJ) are discarded during the production process, resulting in a waste of resources. Existing studies have demonstrated that the FROJ serves as an important resource for functional food and pharmaceutical applications. However, the application effects of FROJ as a feed resource in livestock remain unclear. This study aimed to evaluate the effects of FROJ on in vitro ruminal fermentation, antioxidant capacity, and microbial communities in yaks. The results showed that dietary FROJ significantly increased the total volatile fatty acids (VFAs), the proportion of acetic acid, and propionic acid compared to the hay group. Furthermore, dietary FROJ significantly reduced the yak's rumen malondialdehyde (MDA) content and significantly increased superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity in the rumen fluid. It also significantly increased the relative abundance of Firmicutes, Actinobacteriota, and unclassified_Lachnospiraceae, as well as the Firmicutes to Bacteroidetes ratio in yak rumen. Spearman's correlation analysis of the microbiota, rumen fermentation parameters, and antioxidant capacity revealed positive and negative regulatory mechanisms. In conclusion, dietary FROJ can improve ruminal fermentation and antioxidant capacity in yaks, and this improvement may be associated with an increase in potentially beneficial microbiota. Our findings indicate that the FROJ can be utilized as a feed supplement for ruminants, serving to enhance their immune responses and alleviate the resource wastage.