Rearing conditions affected responses of weaned pigs to organic acids showing a positive effect on digestibility, microflora and immunity.

Three experiments were conducted to assess the response of weaned pigs to organic acid SF3, which contains 34% calcium formate, 16% calcium lactate, 7% citric acid and 13% medium chain fatty acids. Dietary treatments had no effect on growth performance of piglets (21-day weaning) fed the commercial prestart diet for 1 week before receiving the experimental diets supplemented with SF3 at 0, 3 or 5 g/kg diet (Exp. 1), whereas diarrhea frequency averaged across a week was decreased by SF3 supplementation (5 g/kg diet) in piglets fed the experimental diets immediately after weaning (Exp. 2). In Exp. 3, piglets (28-day weaning) were fed the control (containing pure colistin sulfate and enramycin, respectively, at 20 mg/kg diet) for 1 week and then were fed the control or SF3-supplemented (5 g/kg diet) diet for 2 weeks. The SF3-fed piglets had greater apparent ileal digestibility of calcium and dry matter, while also demonstrating greater overall gross energy, up-regulated jejunal expression of sodium-glucose cotransporter-1 and transforming growth factor-β, down-regulated jejunal expression of tumor necrosis factor (TNF)-α, higher ileal Lactobacillus, with lower total bacteria content, lower plasma TNF-α but higher IgG levels than the control-fed piglets. Collectively, SF3 consumption improved diarrhea resistance of weaned pigs by improving nutrient digestibility, piglet immunity and intestinal bacteria profile. © 2016 Japanese Society of Animal Science.