Dietary L-glutamine supplementation improves growth performance, gut morphology, and serum biochemical indices of broiler chickens during necrotic enteritis challenge

Necrotic enteritis (NE) causes significant economic losses in the broiler chicken industry, especially in birds raised without in-feed antibiotics. L–glutamine (Gln) is an amino acid that may compensate for metabolic losses from infection and improve the intestinal development. This study investigated the effects of dietary Gln (10 g/kg) supplementation on growth performance, intestinal lesions, jejunum morphology, and serum biochemical indices of broiler chickens during NE challenge. The study employed a factorial arrangement of treatments with factors: NE challenge, no or yes; dietary Gln inclusion, 0 g/kg in starter (S), d 0 to 10, grower (G) d 10 to 24, and finisher (F) d 24 to 35; 10 g/kg in S, G, F, or 10 g/kg in S, G only. Each treatment was replicated in 6 floor pens with 17 birds per pen as the experimental unit for performance and 2 birds for other measurements. Challenge significantly reduced bird performance, increased incidence of intestinal lesions, and affected intestinal development and serum biochemical indices. Regardless of challenge, Gln supplementation increased gain (𝑃 < 0.05), feed intake (𝑃 < 0.05), and decreased FCR (𝑃 < 0.05) on d 24. On d 35, Gln improved gain (𝑃 < 0.05) and FCR (𝑃 < 0.001) whereas withdrawing Gln from finisher tended to diminish the beneficial effect on weight gain but not FCR. Dietary Gln reduced lesion scores in the jejunum (𝑃 < 0.01) and ileum (𝑃 < 0.01) in challenged birds. On d 16, Gln increased villus height to crypt depth ratio in unchallenged birds (𝑃 < 0.05) and reduced crypt depth of challenged birds on d 24 (𝑃 < 0.05). Regardless of challenge, supplementation with Gln reduced crypt depth on d 16 (𝑃 < 0.05), and increased villus height (𝑃 < 0.01) and the villus height to crypt depth ratio (𝑃 < 0.001) on d 24. Dietary Gln lowered serum uric acid level regardless of challenge (𝑃 < 0.05). The current study indicates that dietary Gln alleviates adverse effects of NE and may be useful in antibiotic-free diets.