Effects Of Astragalus Polysaccharide On The Growth Performance And Immune Function Of Oreochromis-niloticus

The fish of oreochromis-niloticus was the experimental object for this study, using different doses of astragalus polysaccharides in the oreochromis-niloticus basic feed as the experimental feed. The objective was to investigate the astragalus polysaccharide on the growth and immune function of oreochromis-niloticus. Five groups were set: the control group(0mg·kg^-1), group 500(500mg·kg^-1), group 1000(1000mg·kg^-1), group 1500(1500mg·kg^-1), group 2000(2000mg·kg^-1). The experiment results are as follows:1,The period for the growth performance was 40 days, measuring the weight of oreochromis-niloticus every 10 days in all groups(body weight and body length were both measured on the 40th day). The results indicated that the weight increased of the astragalus polysaccharide adding groups were higher than the control group at all stages. Among them, the absolute body weight gain of oreochromis-niloticus in group 1000 and group 1500 were higher than the control group, reaching extremely significant difference level(P<0.01). The body length in each experimental groups were not significant difference with the control group(P>0.05).2,The change of intestinal villus morphology were detected by HE staining method. The purpose was to study the effects of astragalus polysaccharide on intestinal villus length, crypt depth and myometrial thickness of oreochromis-niloticus. The results showed that the intestinal structure was integrity, stage was clear and intestinal villus was neatly arranged in all groups. Among them, the intestinal villus length, crypt depth and myometrial thickness in group 1000 and group 1500 were higher than the control group (P<0.05).3,The distribution and quantitative changes of mast cells were detected by Alcian Blue and Safranine staining in fore-gut, mid-gut and hind-gut. The results showed that the quantities of fore-gut mast cells in group 1000 and group 1500 were higher than the control group(P<0.01). The quantities of mid-gut mast cells in group 1000, group 1500 and group 2000 were higher than the control group (P<0.05). The quantities of hind-gut mast cells in each experimental groups were not significant difference with the control group(P>0.05).4,The distribution and quantitative changes of mucous cells were detected by AB-PAS staining in fore-gut, mid-gut and hind-gut. The results showed that the quantities of fore-gut and mid-gut mucous cells in group 1000 and group 1500 were higher than the control group(P<0.05). The quantities of hind-gut mucous cells in group 1000 and group 1500 were higher than the control group (P<0.01).5,The distribution and quantitative changes of intra-epitheial lymphocytes were detected by HE staining in fore-gut, mid-gut and hind-gut. The results showed that the quantities of fore-gut intra-epitheial lymphocytes in each experimental groups were not significant difference with the control group (P>0.05). The quantities of mid-gut and hind-gut intra-epitheial lymphocytes in group 1000, group 1500 and group 2000 were higher than the control group(P<0.05).6,The quantitative of proliferating cell nuclear antigen positive cells, inducible nitric oxide synthase positive cells and somatostatin positive cells were detected by immunohisto-chemistry antibody in fore-gut and stomach. The results showed that the quantities of PCNA positive cells in group 1000 and group 1500 were higher than the control group(P<0.05). The quantities of iNOS and SS positive cells in group 500, group 1000 and group 1500 were lower than the control group(P<0.05).7,The blood of oreochromis-niloticus was collected from the heart on the 10th day, 20th day and 30th day of the experiment and centrifuged to plasma. Detecting the enzyme activities of acid phosphatase, alkaline phosphatase, total superoxide dismutase, catalase and lysozyme by spectrophotometer and chemical colorimetry methods. The purpose was to study the effects of astragalus polysaccharide on non-specific immunity of oreochromis-niloticus. The results showed that the enzyme activities in all experimental groups were not significant difference with the control group on the 10th day(P>0.05). The enzyme activities in group 1000 and group 1500 were higher than the control group on the 20th day and 30thday (P<0.05).Conclusion: The experiment results indicated that adding astragalus polysaccharide in the feed can not only promote the weight increased and improve the growth performance of oreochromis-niloticus to some extent, but also can increase the quantities of mast cells, mucous cells and intestinel intra-epitheial lymphocytes in the digestive tract and improve the intestinal morphology of oreochromis-niloticus. At the same time it can improve ACP, AKP, T-SOD, CAT and LSZ enzyme activities in plasma, enhance the immune function of oreochromis-niloticus.