355. Award Talk: Effects of Dietary L-glutamate, L-aspartate, and Their Combination on Growth Performance, Diarrhea Severity, Immune Responses, Intestinal Integrity, and Amino Acid Digestibility of Weaned Piglets Challenged with Enterotoxigenic Esche

Abstract L-glutamate (Glu) and L-aspartate (Asp) are functional amino acids that promote intestinal health and resilience. This study investigated their effects on growth performance, diarrhea incidence, intestinal integrity, and nutrient digestibility in weaned pigs challenged with enterotoxigenic Escherichia coli (ETEC). Sixty-five weaned pigs (7.59 ± 1.11 kg BW) were randomly assigned to five treatments (n = 13 per treatment): control (CON), CON + 1% glutamate (GLU), CON + 1% aspartate (ASP), CON + 1% glutamate + 1% aspartate (GAC), and CON + 50 mg/kg carbadox (ABX). All pigs were orally challenged with F18 ETEC (1010 CFU/dose/day) for three consecutive days. The study period lasted for four weeks, with a 7-day adaptation period and 21 days post- inoculation (PI). Growth performance, diarrhea scores, and fecal samples were collected throughout the experiment. Jejunal and ileal mucosa and ileal digesta were collected at specific time points to evaluate intestinal integrity and amino acid digestibility, respectively. All data were analyzed using ANOVA, except that diarrhea frequency was analyzed by Chi-square test, with the individual pig as the experimental unit. On d 21 PI, ASP and GAC supplementation increased (P < 0.05) body weight gain, with ASP group had the highest (P < 0.05) among all groups on d 14 and 21 PI. GLU, ASP, and GAC supplementation improved (P < 0.05) average daily gain (ADG) and gain:feed ratios from d –7 to 21 PI. ASP-fed pigs consistently showed the greatest (P < 0.05) ADG and gain:feed ratios across multiple intervals and increased (P < 0.05) average daily feed intake from d 0 to 14 PI. ASP or GLU supplementation also reduced (P < 0.05) diarrhea scores on d 4 PI and lowered (P < 0.05) overall diarrhea frequency. ASP and GAC supplementation reduced (P < 0.05) fecal β-hemolytic coliforms shedding on d 7 PI, and GAC showed further reductions (P < 0.05) on d 14 PI. On d 5 PI, GLU or ASP supplementation tended to reduce (P < 0.10) ileal CLDN1 while ASP tended to increase (P < 0.10) jejunal OCDN. On d 21 PI, GAC tended to increase (P < 0.10) jejunal MUC2. Moreover, GAC-fed pigs increased (P < 0.05) apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of lysin, Glu, and Asp on d 21 PI, as well as tended to increase (P < 0.10) AID of crude protein and total amino acids. Moreover, ASP- fed pigs increased (P < 0.05) AID of dry matter and both AID and SID of Asp. In conclusion, Glu and/or Asp supplementation improved performance outcomes and alleviated diarrhea during ETEC challenge. These results supported Glu and Asp as conditionally essential amino acids that promoted disease resistance, offering a nutritional strategy to reduce antibiotic dependence in weaned pigs.