| Glutamine (Gln) is the main energy for some rapid divided cells, and it plays important roles in maintaining the structure and function of intestine immune system. Many evidences suggested that supplemental Gln could inhibit the decomposition of body protein, modulate nitrogen balance and improve the antioxidation of body. While Gln is heat labile and the alanyl-glutamine (Ala-Gln) is much more tolerant to high temperature. Solubility is another obvious advantage. The effect of exogenous supplementation of Ala-Gln on intestine development and non-specific immune functions of juvenile German mirror carp (Cyprinus carpio L.) was evaluated. Three hundred and sixty healthy juvenile fish with an average initial weight of 12.97±0.18g were randomly assigned to each of 18 experimental aquaria (100×50×50cm) connected to a closed water and oxygen auto-supplemented system. The experiment was conducted in triplicate. Basal diets were supplemented with 6 concentrations of Ala-Gln, i.e., 0, 0.25%, 0.5%, 0.75%, 1.0%, and 1.5% fed to fish respectively for 12 weeks. The results showed as follows:⑴Dietary supplementation of Ala-Gln significantly enhanced weight gain rate (WGR), protein efficiency ratio (PER), protein productive value (PPV) , whole body protein content and feed efficiency (FE) (P<0.05). The results showed that supplementation of Ala-Gln significantly improved protein synthesis and growth performance.⑵Dietary supplementation of Ala-Gln significantly enhanced intestine Na+, K+-ATPase, digestive enzyme (protease, amylase and lipase) activities, intestine fold height, relative gut length , relative gut weight, hepatopancreas index and hepatopancreas protein content (P<0.05). And these parameters increased significantly with increasing dietary Ala-Gln supplementation levels from 0.0 to 0.75%, while there were no significant differences for Ala-Gln supplementation from 0.75% to 1.5%. The results showed that supplementation of Ala-Gln could imprpve the development of digestive organs and intestinal absorption.⑶Dietary supplementation of Ala-Gln significantly enhanced the activities of superoxide dismutases (SOD) and glutathione peroxidase (GPX) activities, glutathione (GSH) content, and decreased malondialdehyde (MDA) content (P<0.05), while there was no significant differences among groups fed Ala-Gln levels over 0.75%. The results showed that supplemental Ala-Gln could enhance free radical scavenging activity.⑷Serum TP levels significantly improved with increasing dietary Ala-Gln supplementation (P<0.05), while no significant differences observed between 1.0% and 1.5% supplemental groups (P>0.05). Dietary supplementation of 0.75% Ala-Gln significantly improved serum albumin (ALB) and globulin (GLB) levels, and lysozyme (LSZ) activities (P<0.05). Serum C3 and C4 levels significantly improved with dietary Ala-Gln supplementation from 0 to 0.75% (P<0.05), while beyond this levels, both values significantly decreased (P<0.05). Serum akaline phosphatase (AKP), glutamate pyruvate transaminase (GPT), and glutamic oxaloacetic transaminase (GOT) activities were not influenced by supplementation of different levels of Ala-Gln (P>0.05).In summary, the results of this study show that Ala-Gln has a positive effect on the growth performance, intestine development and digestive enzyme activities in juvenile mirror carp; supplemental Ala-Gln improved antioxidant ability through increasing organism GSH content, SOD and GPX activities; supplemental Ala-Gln improved serum LSZ activities, C3 and C4 levels to promote the non-specific immunity of juvenile mirror carp. In conclusion, on the basis of our study, supplementation of Ala-Gln could significantly improve growth performance, intestine development and increase antioxidant ability of juvenile mirror carp, and use of a 0.75% supplement of Ala-Gln was recommended. |
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