381 Effects of L-glutamate and L-aspartate supplementation on intestinal immunity and intestinal barrier integrity of weaned piglets challenged with F18 ETEC

Abstract L-glutamate (Glu) and L-aspartate (Asp) are pivotal components in the cellular metabolic pathways and immune regulation of pigs. This study aimed to investigate the effects of Glu and Asp on systemic and intestinal immune responses of weaned piglets challenged with an enterotoxigenic Escherichia coli (ETEC) F18. Weaned pigs [n = 49; 8.18 ± 1.54 kg body weight (BW)] were randomly assigned to one of seven treatments, with seven piglets per treatment. The treatments included negative control (NC) and positive control (PC) that were fed with control diet without or with ETEC challenge, respectively. The other five dietary treatments were supplemented with either 1% or 2% Glu or Asp, or 50 mg/kg of Carbadox, and were challenged with ETEC. All pigs except for NC were challenged with F18 ETEC orally for three consecutive days at the dose of 1010 CFUּ dose-1ּ d-1. The study period lasted for 3 wk, with a 7-d adaptation period and 14 d post-inoculation (PI). On d 14 PI, jejunal and ileal mucosa were collected to analyze the mRNA expression of inflammatory cytokines and tight junction proteins by quantitative polymerase chain reaction. All data were analyzed with ANOVA using the PROC MIXED of SAS with pig as the experimental unit. Among all treatments, pigs fed with carbadox showed greatest (P < 0.05) mRNA expression of interleukin (IL)10 in jejunal mucosa. Supplementing 2% Asp or carbadox had less (P < 0.05) expression of IL6 than PC in jejunal mucosa, while supplementing 1% Asp had lowest (P < 0.05) expression of IL6 in ileal mucosa. Pigs fed with 1% Glu had greatest (P < 0.05) expression of IL17A and IL22, while pigs fed with 2% Glu had greatest (P < 0.05) expression of IL23 among all treatments in jejunal mucosa. However, dietary treatments did not affect mRNA expression of IL17A, IL22, and IL23 among all treatments in ileal mucosa. Compared with PC, supplementing 1% Asp had greater (P < 0.05) expression of MUC2, OCDN, and ZO1 in ileal mucosa. Supplementation of 2% Glu or 1% Asp had greater (P < 0.05) expression of MUC2 in jejunal mucosa than NC. Among all treatments, pigs fed with 2% Asp showed greatest (P < 0.05) expression of CLDN1 in ileal mucosa, while showed least (P < 0.05) expression of CLDN1 in jejunal mucosa. However, no difference was observed in expression of OCDN and ZO1 in jejunal mucosa. In conclusion, results of the present study indicate that dietary supplementation of Glu or Asp affected both intestinal immunity and integrity of ETEC-challenged weaned pigs with similar trends as the supplementation of carbadox.