Effects of dietary indole-3-acetate sodium on intestinal morphology, nutrient absorption, and inflammatory responses in weaned piglets.

Abstract

Weaning stress can severely damage the piglets' intestines. Microbial tryptophan catabolites play a vital role in maintaining the health of the intestinal mucosa. Indole-3-acetic acid (IAA), an indole derivative with known anti-inflammatory properties, has not yet been studied for its impact on piglets' intestinal health. Twenty-four weaned crossbred piglets (Duroc × Yorkshire × Landrace, weighing 6.58 ± 0.07 kg) were randomly allocated to receive diets containing 0, 120, or 240 mg/kg indole-3-acetate sodium (IAA-Na). Although dietary IAA-Na did not significantly impact growth performance or diarrhea incidence (P > 0.05), the 240 mg/kg IAA-Na elevated jejunal villus width (P < 0.05), tended to increase villus surface area (P < 0.10), and enhanced apparent nutrient digestibility alongside upregulating the mRNA expression of transporters (P < 0.05). Furthermore, dietary IAA-Na promoted intestinal epithelial cell proliferation and reduced secretory cell numbers (P < 0.05). Transcriptomic analysis of the jejunum of the 240 mg/kg group revealed significant modulation of pathways related to the "inflammatory response" and "immune system processes." Consistent with this, dietary supplementation with 240 mg/kg IAA-Na downregulated the content and expression of proinflammatory cytokines while upregulating the content and expression of anti-inflammatory cytokines in the jejunum. To further elucidate the effect of IAA on epithelial renewal, piglet jejunal organoids were employed as an in vitro model. Treatment with 0.5 and 2 μM IAA-Na significantly increased the organoids budding rate on d 3 (P < 0.01), indicating enhanced epithelial renewal capacity. In conclusion, although dietary IAA did not improve overall growth performance, 240 mg/kg IAA-Na promoted nutrient absorption in weaned piglets, potentially through enhancing anti-inflammatory responses and epithelial renewal. Weaning stress can impair the intestinal morphology and function of pigs, leading to diarrhea and reduced growth performance. Indole-3-acetic acid (IAA) is increasingly recognized for its anti-inflammatory effects in rodents, particularly with regard to modulating immune homeostasis and intestinal microbiota. In this study, indole-3-acetate sodium (IAA-Na) was added to the piglets’ basal diet at concentrations of 120 and 240 mg/kg. Although dietary supplementation with IAA-Na did not significantly improve growth performance or reduce diarrhea significantly in piglets, it did promote the proliferation of intestinal epithelial cells, enhance intestinal nutrient digestion and absorption, and boost the immune function in weaned piglets. These findings suggest that IAA-Na is a promising novel strategy for improving intestinal health in piglet production.