Effect of dietary supplementation with glutamine and a combination of glutamine-arginine on intestinal health in twenty-five-day-old weaned rabbits

The effect of dietary supplementation with 1% L-glutamine and a combination of 1% L-glutamine and 0.5% L-arginine on intestinal health was examined in weaned rabbits. A basal diet was formulated to meet nutrient recommendations. Another 2 diets were formulated by adding 1% (as-fed basis) Gln or a mixture of 1% (as-fed basis) Gln + 0.5% (as-fed basis) Arg (Gln-Arg) to the basal diet. In Exp. 1, a total of 357 rabbits were blocked by litter and assigned at random to the experimental diet to determine mortality ( 119 per diet) and growth performance ( 35 per diet; from weaning at 25 to 56 d of age). Rabbits were fed the experimental diets for a 2-wk period and thereafter received a commercial diet. Rabbits weaned at 25 d ( blocked by litter and assigned at random to diets) were slaughtered at 35 d and used to determine apparent ileal digestibility of DM, CP, and AA ( Exp. 2, a total of 60 rabbits), intestinal morphology, N-aminopeptidase and myeloperoxidase intestinal activity, the expression of PPAR. at the ileum and kidney, serum immunoglobulin in healthy and sick rabbits ( Exp. 3, a total of 24 rabbits), and ileal and cecal microbial composition by PCR-RFLP ( Exp. 4, a total of 45 rabbits). Dietary treatment did not affect ADG, ADFI, or G: F, during the entire fattening period. Supplementation with Gln reduced mortality during the first 2 wk and the whole fattening period from 18.5 to 8.4% ( P = 0.023) and from 31.9 to 20.2% ( P = 0.039), respectively, whereas no effect was detected for Arg supplementation. Among all the variables studied, the reduction on mortality due to Gln was related to a reduced intestinal colonization ( Eimeria lesions) and changes on microbial ecosystem in the ileum and cecum, reducing the frequency of detection of Clostridium spp. ( from 86.7 to 33.3%, P = 0.003) at the ileum, and Helicobacter spp. at the ileum ( from 86.7 to 46.7%, P = 0.003) and at the cecum ( from 86.7 to 46.7, P = 0.028), whereas no effect was detected for Arg supplementation. In conclusion, 1% L-Gln supplementation to postweaned rabbit diets decreased fattening mortality and modified the intestinal microbiota ( although no consistent effects were observed on mucosal histology or inflammatory and systemic immune response). Diets containing a combination of 1% Gln and 0.5% Arg were of little additional benefit.