Abstract
The addition of glycerin, vitamin C, and niacinamide to pig diets increased the redness of longissimus dorsi; however, it remains unclear how these supplements affect gut microbiota and metabolites. A total of 84 piglets (20.35 ± 2.14 kg) were randomly allotted to groups A (control), B (glycerin-supplemented), C (vitamin C and niacinamide-supplemented), and D (glycerin, vitamin C and niacinamide-supplemented) during a feeding experiment. Metagenomic and metabolomic technologies were used to analyze the fecal compositions of bile acids, metabolites, and microbiota. The results showed that compared to pigs in group A, pigs in group D had lower virulence factor expressions of lipopolysaccharide (p < 0.05), fatty acid resistance system (p < 0.05), and capsule (p < 0.01); higher fecal levels of ferric ion (p < 0.05), allolithocholic acid (p < 0.01), deoxycholic acid (p < 0.05), tauroursodeoxycholic acid dihydrate (p < 0.01), glycodeoxycholic acid (p < 0.05), L-proline (p < 0.01) and calcitriol (p < 0.01); and higher (p < 0.05) abundances of iron-acquiring microbiota (Methanobrevibacter, Clostridium, Clostridiaceae, Clostridium_sp_CAG_1000, Faecalibacterium_sp_CAG_74_58_120, Eubacteriales_Family_XIII_Incertae_Sedis, Alistipes_sp_CAG_435, Alistipes_sp_CAG_514 and Methanobrevibacter_sp_YE315). Supplementation with glycerin, vitamin C, and niacinamide to pigs significantly promoted the growth of iron-acquiring microbiota in feces, reduced the expression of some virulence factor genes of fecal pathogens, and increased the fecal levels of ferric ion, L-proline, and some secondary bile acids. The administration of glycerol, vitamin C, and niacinamide to pigs may serve as an effective measure for muscle redness improvement by altering the compositions of fecal microbiota and metabolites.