Effects of butyric acid and resistant starch supplementation on gut microbiota, fermentation and growth in weanling pigs fed propionic acid-preserved grain

Weaning is a critical developmental period during which piglets experience disturbances in gut health, intestinal function and growth performance. A 2 × 2 factorial study evaluated the effects of propionic acid (PA)-preserved grain and dietary supplementation with butyric acid (BA) and resistant potato starch (PS) on post-weaning piglet growth and gut health, with the hypothesis that their combined use would result in the greatest improvements. Grain was dried conventionally or preserved using 4 g/kg of PA. One hundred and forty-four weaned piglets (28 days old) were randomly allocated to: (T1) dried grain diet; (T2) PA-preserved grain diet; (T3) dried grain diet + 1.5% BA and 1% PS; and (T4) PA-preserved grain diet + 1.5% BA and 1% PS. Growth was monitored for 35 days, and intestinal morphology, digesta microbiota, and volatile fatty acid (VFA) profiles were assessed on day 8 (n = 12). Despite containing higher levels of deoxynivanol than dried grain, PA-preserved grain improved average daily feed intake, average daily gain, and body weight (P < 0.05). These improvements coincided with increased caecal Gemmiger , caecal Alloprevotella and Faecalibacterium in the caecum and colon , but also with higher Proteolytic bacteria , colonic branched-chain fatty acid concentrations, and a greater diarrhoea incidence (P < 0.05). Supplementing BA + PS did not affect growth or diarrhoea, but increased multiple butyrate-producing taxa including caecal Roseburia , and Faecalibacterium in the caecum and colon (P < 0.05). When added to the dried grain diet, BA + PS improved overall gain-to-feed ratio and total caecal VFA concentrations (P < 0.05), whereas no additional benefit were observed when combined with PA-preserved grain. In conclusion, PA-preserved grain enhanced piglet growth, while BA + PS improved gut microbial populations and may represent a practical strategy to improve gut function and growth in conventional diets. • PA-preserved grain improved piglet feed intake growth and body weight. • PA-preserved grain increased colonic Gemmiger . • BA + PS supplementation increased caecal Roseburia and Faecalibacterium . • BA + PS improved feed efficiency and caecal VFA levels in piglets fed dried grain. • There was no complementary benefits when BA + PS combined with PA-preserved grain.