Growing Tibetan Pigs Adapt to High-Fiber Diets by Enhancing Fiber Degradation Capacity

The systematic analysis of the synergistic mechanism between microbial fiber-degrading enzymes and short-chain fatty acids under high-fiber diet conditions is limited. In this study, we evaluated the effects of a high-fiber diet on the growth performance, nutrient digestibility, blood and serum metrics, cellulase/hemicellulase activity, and fecal microbial composition of growing Tibetan pigs. Forty Tibetan pigs were allocated to a control group (CON, 5% crude fiber) or a high-fiber group (HF, 10% crude fiber) based on crude fiber levels as a blocking factor. The pre-trial period was 7 d, and the formal trial lasted 28 d. The HF group showed significantly higher fecal cellulase and hemicellulase activities than those of the CON group (P < 0.05). Additionally, the HF group showed significantly elevated levels of acetic, propionic, and butyric acids, as well as increased relative abundances of Fibrobacter and p-75-a5 in the feces (P < 0.05). The correlation analysis revealed that Fibrobacter exhibited significant positive correlations with acetic acid, butyric acid, cellulase, and hemicellulase, whereas p-75-a5 was significantly positively correlated with hemicellulase (P < 0.05). In conclusion, this study revealed that a high-fiber diet significantly enhanced short-chain fatty acid production in Tibetan pigs by selectively enriching obligate fiber-degrading bacteria and upregulating key fiber-digesting enzymes.