Comparative study on the effects of glutamic acid and glutamine in promoting intestinal development in chicks through energy metabolism.

Objective: This study evaluated the effects of glutamic acid (Glu) and glutamine (Gln) on the intestinal development of layer chicks with lipopolysaccharide (LPS)-induced damage.

Methods: A total of 240 healthy 0-d-old Hy-Line Brown chicks were randomly assigned to 4 treatments, each with 6 replicates. At 8 and 11 d of age, all birds (except for the control group) received two administrations of LPS. The LPS-challenged birds were divided into three dietary treatment groups: a basal diet (without additives), a 0.05% Glu-supplemented diet, and a 0.20% Gln-supplemented diet.

Results: The LPS challenge induced intestinal injury and suppressed intestinal development in layer chicks, as evidenced by significantly reduced growth performance, poor intestinal parameters, and morphology (p<0.05). Compared to the LPS group, dietary supplementation with 0.05% Glu and 0.20% Gln significantly enhanced average daily gain (ADG), average daily feed intake (ADFI), body weight (BW), and intestinal development parameters (including length, weight, villus height, villus height/crypt depth) of duodenum, jejunum and ileum (p<0.05). These results could be attributed to upregulated mRNA expression levels of Mucin-2, E-cadherin, Dclk-1, Vil-1, Lysozyme, ChgA, Lgr-5, Bmi-1, ATP5F1AZ, and β-catenin (p<0.05). Furthermore, dietary supplementation with 0.20% Gln outperformed 0.05% Glu in enhancing BW, ADG, and ileum parameters (weight, length, epithelial cell count, and energy metabolism) (p<0.05). Additionally, intestinal organoids supplemented with 10 μM Gln had significantly higher mean area, E-cadherin gene expression, and ATP content compared with those treated with 5 μM Glu in vitro (p<0.05).

Conclusion: Dietary supplementation with 0.05% Glu and 0.20% Gln could improve growth performance, intestinal development, and repair intestinal damage in layer chicks through enhanced epithelial proliferation and differentiation. Moreover, 0.20% Gln performed better than 0.05% Glu, which may be attributed to superior energy metabolism.