Effects of Butyric Acid Supplementation on the Gut Microbiome and Growth Performance of Weanling Pigs Fed a Low-Crude Protein, Propionic Acid-Preserved Grain Diet

Reducing crude protein (CP) in weaner pig diets lowers post-weaning diarrhoea risk but may impair growth performance. This study aimed to identify benefical effects of organic acid (OA)-preserved grain and butyric acid (BA) supplementation on gut health and growth in low-CP diets. At harvest, grain was divided into 2 batches: one dried at 65 °C, the other treated with a propionic acid. Ninety-six piglets (28 days old) were assigned to four treatments: (1) dried grain, (2) OA-preserved grain, (3) dried grain+3% BA, and (4) OA-preserved grain+3% BA. On day 8, microbial composition, inflammatory markers, volatile fatty acids, and intestinal morphology were assessed. The OA-preserved diet improved feed conversion ratio (P < 0.05), increased beneficial gut bacteria (P < 0.01), elevated caecal butyrate (P < 0.05), reduced jejunal CXCL8 expression (P < 0.05), and enhanced nutrient digestibility (P < 0.01). BA reduced feed intake (P < 0.05), improved nutrient digestibility (P < 0.01), decreased colonic Proteobacteria (P < 0.05), and increased colonic propionate and butyrate (P < 0.01). Combining OA-preserved grain with BA elevated ileal Proteobacteria and Pasteurellaceae (P < 0.05). In conclusion, while OA-preserved grain improves feed efficiency, nutrient digestibility, and gut microbiota, and suplementing butyric acid enhances nutrient digestibility but reduces feed intake, their combination may disrupt microbial balance.