Impact of inulin supplementation and animal density modulation on intestinal health parameters in weaned piglets

Social stress in piglets poses welfare and production issues for the pig industry. Through the gut-brain axis, social stress relates with intestinal health. This study evaluated the combined effects of inulin and chronic social stress on molecular, physiological, and production-level indicators of intestinal health in piglets.
A total of 144 piglets, sex ratio 50:50, were weaned at 4 weeks of age and fed for 4 weeks a control or inulin diet (nutrient adequate with 0 or 10g inulin/kg feed) in 12 pens with high (n=14) or low (n=10) animal densities (2.75 vs 1.96 pigs/m²). At 8 weeks of age, 12 piglets/treatment were slaughtered for intestinal sampling. Inflammatory and permeability gene expression (qPCR) and histomorphological structure were analysed in intestinal tissue. Short-chain fatty acids (SCFA) were measured (HPLC) in intestinal content. Outliers were removed using QQPlot, and ANOVA was performed. Body weight, feed intake and histomorphology showed no differences between treatments. In the colon, BAX, IL1α and IL6 expression decreased with inulin (P<0.05) but IL1α increased in high density pens (P<0.05). No diet-density interaction was found for any of the parameters. In the ileum, TANK expression decreased with high density (P<0.05). SCFA profiles showed higher molar ratio of isobutyric acid in the colon and higher acetic acid molar amounts in the jejunum of inulin fed pigs while high density lowered molar amounts of propionic acid in the jejunum (P<0.05).
Inulin showed anti-inflammatory effects while, oppositely, high animal density activated the NFκB pathway. Despite molecular signs of social stress and the effect of inulin, piglet performance was minimally impacted, likely due to insufficient stressor and a low inulin inclusion rate. No significant interactions between inulin and density were found, suggesting each affects intestinal health independently. Addressing high density stress remains critical for improving gut health and performance in piglets.