PSVI-21 Effects of L-glutamate and L-aspartate supplementation on immune responses of weaned piglets challenged with F18 ETEC.

Abstract L-glutamate (Glu) and L-aspartate (Asp) play key roles in enterocyte metabolism and act as immunomodulators in pigs. This study aimed to explore the effects of Glu and Asp on the immune responses of weaned piglets challenged with F18 enterotoxigenic Escherichia coli (ETEC). A total of forty-nine weaned pigs (8.18 ± 1.54 kg 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 the control diet. The other five dietary treatments were supplemented with either 1% or 2% Glu or Asp, or 50 mg/kg of Carbadox. All pigs except for NC were challenged with F18 ETEC orally for three consecutive days at the dose of 1010 CFU/dose/day. The study period lasted for three weeks, with a 7-day adaptation period and 14 days post-inoculation (PI). Blood samples were collected on d 0 before ETEC inoculation, and on d 2, 5, and 14 PI to analyze the white blood cell profile. On d 14 PI, jejunal and ileal mucosa were collected to analyze the mRNA expression of inflammatory cytokines by quantitative reverse transcription polymerase chain reaction. All data were analyzed with ANOVA using the PROC MIXED of SAS with the pig as the experimental unit. On d 2 PI, 1% Glu supplementation had the lowest (P < 0.05) neutrophil-to-lymphocyte ratio among the seven groups and exhibited a lower (P < 0.05) ratio than 2% Asp supplementation. On d 5 PI, pigs fed 2% Glu or 2% Asp had higher (P < 0.05) neutrophil-to-lymphocyte ratio compared with the carbadox group, while 1% Glu or 1% Asp supplementation resulted in a similar effect to that of pigs fed carbadox. 2% Glu supplementation tended to result in the highest (P < 0.1) neutrophil levels compared to the other groups on d 5 PI. Compared with PC, pigs fed 2% Asp had decreased (P < 0.05) jejunal IL-6 expression on d 14 PI. Pigs fed 1% Glu or 2% Asp had higher (P < 0.05) ileal IL-12 expression than PC and carbadox groups on d 14 PI. Moreover, 2% Glu or 2% Asp supplementation reduced (P < 0.05) jejunal IL-12 expression compared with the PC group. Additionally, 2% Glu supplementation had the lowest (P < 0.05) ileal IFN-γ expression among the seven groups and had lower (P < 0.05) than the carbadox group. Furthermore, pigs fed 1% Glu exhibited the highest (P < 0.05) levels of jejunal IL-17A and jejunal IL-22 among all groups, with higher (P < 0.05) expression than NC and carbadox groups. In conclusion, the results of this study indicate that dietary supplementation with Glu or Asp modulates immune responses in ETEC-challenged weaned pigs.