Role of Metabolomics and Metagenomics in the Replacement of the High-Concentrate Diet with a High-Fiber Diet for Growing Yushan Pigs

The objective of this study was to investigate the regulatory effects of a high-fiber content feed on the productive performance, meat quality, and fat acid composition. A total of 18 120-day-old Yushan pigs with similar initial body weight were randomly allotted into high-concentrate diet (high energy, HE) and high-fiber diet (low energy, LE) treatments for the determination of regulatory effects on productive performance, meat quality, and fatty acid content. Further, blood metabolomic, gut microbiota, and liver energy-related gene expression measurements were used to investigate the underlying mechanisms. Results showed that the LE treatment significantly increased ADFI while decreasing carcass weight, fat percentage, and IMF. Metabolomic results showed that the high-fiber treatment significantly down-regulated metabolites that participated in lipid metabolism such as cyclic ADP-ribose and hippuric acid, while up-regulated metabolites were mainly enriched in nitrogen metabolism such as DL-arginine and propionylcarnitine (<i>p</i> < 0.05). Microbial results showed relative abundances of <i>Lactobacillus</i> and <i>Bifidobacterium</i> are significantly proliferated in the high-fiber feeding treatments (<i>p</i> < 0.05). Transcriptomic results showed that genes mainly enriched into the lipid metabolism are significantly up-regulated under the high-fiber dietary treatment (<i>p</i> < 0.05). Conclusion: higher dietary fiber significantly reduced dietary energy provision, effectively decreased the backfat and abdominal fat content of Yushan pigs through proliferating intestinal fiber-degradable bacteria, and up-regulating the hepatic lipolysis-related gene expression.