| Curcumin is a low molecular weight polyphenolic compounds extracted from the rhizome of Zingiberaceous plants —turmeric(Curcuma longa L.), which is the main active ingredient for turmeric to play the pharmacological effects. It has multiple biological functions of anti-oxidation, anti-bacterial, anti-inflammatory, etc., and its color is stable, almost non-toxic.Large yellow croaker(Pseudosciaena crocea) is one of the most important marine economic fish in our country. In recent years, due to the continuous expansion of the scale of artificial intensive farming, disease problem of large yellow croaker has been increasingly serious. However, the antibiotics and the chemical drugs of insecticides were indiscriminately used and abused, triggering a series of environmental problems. Therefore, seeking the green and environmentally friendly, safe and efficient immunostimulant to ensure the sustainable development of the aquaculture industry of large yellow croaker has great significance.The large yellow croaker was regared as the experimental subject in the study and three experimental groups(amount of curcumin were 100,150,300 mg/kg) and a control group were set to study respectively the effects of dietary curcumin on growth, liver function, intestinal structure, the physiology and biochemistry in serum and skin mucus, phosphatase activities of the tissues and the contents of serum cytokine and other non-specific immunity index and disease resistance of large yellow croaker. It is aimed to provide scientific and theoretical basis for the development and utilization of the immunostimulant of large yellow croaker. The main results of this study are as follows: 1 Effects of dietary curcumin on growth, liver function and intestinal structure in Pseudosciaena croceaAfter feeding dietary curcumin for 45 days, the samples were collected to detect effects of dietary curcumin on growth, liver function and intestinal structure in Pseudosciaena crocea. The results showed that, compared with the blank control group, groups of dietary curcumin significantly(P<0.05, the same as below) increased the survival rate, the specific growth rate, the weight gain rate plus with the condition factor, and remarkably decreased the feed conversion ratio. In addition, dietary curcumin had no effect on the weight of liver, the activities of aspartate aminotransferase(AST) and alanine aminotransferase(ALT) of liver and serum in each experimental group(P>0.05, the same as below). But, dietary curcumin supplement levers with 300 mg/kg significantly decreased hepatosomatic index. When dietary curcumin supplement levers were 100 mg/kg, it remarkably affected the muscular thickness, villus height and crypt depth of the fore-intestine. Dietary curcumin supplement levers with 150 mg/kg had significant effects on the muscular thickness, villus height, crypt depth and the ratio of villus height and crypt depth(V/C) added with the muscular thickness and the ratio of V/C of the mid-intestine. What’s more, the muscular thickness, villus height, crypt depth and the ratio of V/C of the fore-intestine, the muscular thickness, villus height and the ratio of V/C of the mid-intestine plus with the muscular thickness of the hind-intestine were all remarkably affected by dietary curcumin supplement levers with 300 mg/kg. Comprehensive comparison, a dose of curcumin can improve the growth performance of large yellow croaker, and does not damage the function of the liver and can promote the growth of the intestine. The effects of dietary curcumin supplement levers with 300 mg/kg were better comparied with the other doses. 2 Effects of dietary curcumin on non-specific immunity in blood and skin mucus and disease resistance in Pseudosciaena croceaAfter feeding for 30 days and 45 days respectively, the blood was collected to detect phagocytic activity of leucocytes in blood of large yellow croaker. Meanwhile, the serum and the skin mucus were used to detect lysozyme(LZM) activity and antibacterial activity(Ua). In addition, the serum was also used to detect alkaline phosphatase(AKP), acid phosphatase(ACP), superoxide dismutase(SOD) activity and the content of nitric oxide(NO). At the same time, the large yellow croakers were challenged with Vibrio alginolyticus. The results showed that, compared with the blank control group, after feeding for 30 days, the effects of dietary curcumin on LZM activity and Ua of skin mucus as well as the AKP activity and the content of NO in serum were not significant, but it significantly affected phagocytic activity of leucocytes, Ua, LZM, ACP and SOD activility in serum. After feeding for 45 days, the effects of dietary curcumin significantly affected phagocytic activity of leucocytes, LZM activility of skin mucus and serum, Ua, the contents of NO, ACP and SOD activities in serum. The results of Vibrio alginolyticus challenged showed that the fish fed diets with curcumin had significantly lower cumulative mortality(66.67%, 62.22% and 48.89%, respectively) than the control group(84.85%).The results suggested that the dietary curcumin significantly improved the non-specific immunity and disease resistance of of Pseudosciaena crocea, especially feeding dietary curcumin with 300 mg/kg for a long time. 3 Effects of dietary curcumin on phosphatase activities and the contents of serum cytokines in Pseudosciaena croceaThe samples were respectively collected on the 30 th days and the 45 th days to detect the activities of acid phosphatase(ACP) and alkaline phosphatase(AKP) in different tissues plus with the contents of serum cytokines of Pseudosciaena crocea. The results showd that, compared with the control group, when dietary curcumin supplement levers were 100 mg/kg, the ACP activities of liver and fore-intestine plus with the AKP activities of gill, stomach, muscle and liver were significantly increased. Dietary curcumin supplement levers with 150 mg/kg affected the activities of ACP in muscle, liver and fore-intestine as well as the activities of AKP in gill, stomach, muscle, liver and fore-intestine. When dietary curcumin supplement levers were 300 mg/kg, the ACP and AKP activities of hind-intestine plus with the AKP activity of mid-intestine were insignificant(P>0.05, the same as below). At the same time, the ACP and AKP activities in other tissues were significantly increased. In addition, compared with the control group, only the contents of TNF-αwere significantly increased when dietary curcumin supplement levers were 100 mg/kg. The contents of GM-CSF, IL-2 and TNF-αwere all significantly increased when dietary curcumin supplement levers were 150 or 300 mg/kg. Besides, in term of the contents of IFN-γ, there were no significant differences among the three groups, but they decreased in the two periods. On the whole, the dietary curcumin supplement levers with 300 mg/kg had a better effect on phosphatase activities in different tissues and the contents of serum cytokines in Pseudosciaena crocea. |
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