Abstract: Objective: To ascertain the effect of dietary leucine supplementation on intestinal immune function in ultra-early weaned piglets suffering from intrauterine growth retardation (IUGR). Methods: Sixteen normal birth weight (NBW) piglets weaned at 14 days of age and sixteen IUGR newborn piglets were selected according to their birth weight. All the piglets were randomly divided into four groups with 8 replicates in each group, and fed control diet alone or supplemented with 0.35% L-leucine for 21 days, respectively. Results: Compared with NBW piglets, IUGR piglets showed significantly lower lysozyme activity and complement-3 (C3) level in the serum (P < 0.05), a significant reduction in the number of goblet cells (GC) and intraepithelial lymphocytes (IEL) in the jejunum and ileum (P < 0.05) and interleukin-10 (IL-10) content in the ileum, and a significant increase intumor necrosis factor-α (TNF-α) content in the ileum (P < 0.05). In addition, IUGR piglets had significantly increased TNF-α mRNA expression but significantly decreased IL-10 mRNA expression (P < 0.05). Dietary supplementation with 0.35% L-leucine significantly increased lysozyme activity and the levels of C3 and C4 in the serum, the numbers of GC in the ileum and IEL in the duodenum and jejunum, IL-10 content in the ileum, and the mRNA expression of IL-2 and IL-10 in the ileum of IUGR piglets (P < 0.05). Conclusion: IUGR could induce intestinal mucosal inflammatory response and hinder intestinal growth and development in early weaned piglets. L-Leucine could effectively alleviate intestinal mucosal injury caused by IUGR, and improve intestinal immune function in piglets.

Key words: L-leucine, intrauterine growth retardation (IUGR), intestine, immune function, early weaned piglets