Effects Of Antimicrobial Peptides(AMPs) On Growth Performance And Immune Function In Jian Carp(Cyprinus Carpiovar.Jian)

Antimicrobial peptides(AMPs) is an immunopotentiator, which has broad-spectrum antibacterial effect. AMPs have been used in livestock, and more researches demonstrated that AMPs can promote the growth and immune function of piglets and poultry. However, little research was done in aquatic animals. The study on effects of AMPs on growth, muscle quality and immune function in fish is scant, especially the relationship of growth and immune function. Then, the study was designed to explore the effects of AMPs on growth, muscle quality and immune function in Jian carp from the angle of apparent traits, biochemistry, molecular biology. The Jian carp(Cyprinus carpio var.Jian) as research object and 300 healthy fishes in the same size of 87.98 ± 2.26 g were chosen for experiment. The Jian carps were randomly divided into 5 groups and triplicate was set in each group. The Jian carps were fed in 15 aquariums. The experiment was conducted in a temperature-controlled mono-circulated farming system. AMPs was mixed sufficiently into the basal feed at the ratio of 0, 100, 200, 400 and 600 mg/kg according to the formulation of Jian carp. Feeding rate was regulated weekly according to growth and feed intake. The experiment lasted 60 days. Body weight and body length were recorded after 24 h starvation at the end of experiment. 18 fishes from each group were sampled randomly and blood sample was taken from caudal vein.The dorsal muscle and liver of Jian carp were sampled after recording the visceral weight. Five experiments were conducted to study the effects of antimicrobial peptides on growth performance, muscle composition, blood biochemical parameters, activities of antioxidant enzyme and immune-related enzymes, cytokines and related gene expression in the Jian carp. Our study provides a reference for the application effect and mechanism research of AMPs in feed of the Jian carp.1、The results showed as follows that the final weight and specific growth rate with AMPs of 100, 200 and 400 mg/kg groups were significantly higher than the control(P<0.05), the feed conversion ratio was significantly lower than the control(P<0.05). The weight gain rate with AMPs of 400 mg/kg group was significantly higher than the control(P<0.05). The activity of protease with AMPs of 200 and 400 mg/kg groups were significantly higher than the control(P<0.05). The kidney index with AMPs of 400 and 600 mg/kg groups was significantly lower than the control(P<0.05). The correlation analysis showed that significant positive correlation was detected between final weight and weight gain rate, specific growth rate(P<0.01). Significant positive correlation was detected between weight gain rate and specific growth rate(P<0.01). Significant negative correlation was detected between feed conversion ratio and final weight, weight gain rate, specific growth rate(P<0.05). Significant positive correlation was detected between activity of protease and final weight, weight gain rate, specific growth rate(P<0.05).2、The results showed that the content of crude protein and calcium in muscle with AMPs of 400 mg/kg groups was significantly higher than the control(P<0.05). The content of phosphorus in muscle with AMPs of 100, 200 and 400 mg/kg groups was significantly higher than the control(P<0.05). The contents of moisture, crude fat and ash in muscle were not significant differentin each group(P>0.05). The content of proline and cysteine in muscle with AMPs of 100, 200 and 400 mg/kg groups was significantly higher than the control(P<0.05). The content of total amino acid and essential amino acid was reduced in muscle with AMPs of 600 mg/kg groups. The EPA and DHA content with AMPs of 100 and 200 mg/kg groups was significantly higher than the control(P<0.05). The DPA content with AMPs of 100 groups was significantly higher than the control(P<0.05). The content of total protein, albumin and total cholesterol with AMPs of 600 mg/kg groups was significantly lower than the control(P<0.05). The content of glycerin trilaurate with AMPs of 200, 400 and 600 mg/kg groups was significantly lower than the control(P<0.05).3、The results showed that the activity of superoxide dismutase in serum with AMPs of 100 mg/kg groups was significantly higher than the control and 600 mg/kg groups(P<0.05). The activity of catalasein serum with AMPs of 100, 200 and 400 mg/kg groups was significantly higher than the control and 600 mg/kg groups(P<0.05). Significant positive correlation was detected between superoxide dismutase activity and catalase activity(P<0.01). The the activity of alkaline phosphate in serum with AMPs of 600 mg/kg group was significantly lower than the control(P<0.05). The activity of acid phosphatase in serum with AMPs of 100 mg/kg group was significantly higher than the control(P<0.05). The lysozyme activity in serumwith AMPs of 100, 200 and 400 mg/kg groups were significantly higher than the control and 600 mg/kg group(P<0.05). The content of immunoglobulin M(Ig M) and interleukin(IL)-1β with AMPs of 100 mg/kg groups was significantly higher than the control and other groups(P<0.05). IL-1α content with AMPs of 100 mg/kg group was significantly higher than the control group, 400 and 600 mg/kg groups(P<0.05). The correlation analysis showed that significant positive correlation was detected between Ig M and IL-1ɑ, IL-1β of serum(P<0.01).Significant positive correlation was detected between IL-1ɑ and alkaline phosphate activity, lysozyme activity of serum(P<0.05). Significant positive correlation was detected between IL-1β and alkaline phosphate activity, lysozyme activity of serum(P<0.05).Significant positive correlation was detected between MHC and alkaline phosphate activity of serum(P<0.01).4、The results showed that the IGF-1m RNA relative expression levels of hepatopancreas tissue in Jian carp with AMPs of 200 and 400 mg/kg groups were significantly higher than the control and the 600 mg/kg group(P<0.05). The IL-1βm RNA relative expression levels of hepatopancreas tissue in Jian carp with AMPsof 100 and 200 mg/kg groups were significantly higher than the control(P<0.05). The correlation analysis showed that significant positive correlation was detected between SGR and IGF-Im RNA expression, IL-1βm RNAexpression(P<0.05). Significant positive correlation was detected between SGR and Ig M content, IL-1β content(P<0.05). Significant negative correlation was detected between FCR and IL-1βm RNA expression(P<0.05). IGF-Im RNA expression and acid phosphatase activity, lysozyme activity in serum were significant positive correlation(P<0.01). Significant positive correlation was detected between IL-1βm RNA expression and Ig M level(P<0.01). Ig M and IL-1β content in serum were significant positive correlation(P<0.05).In conclusion, the AMPs can promote the growth of the Jian carp, reduce the content of glycerin trilaurate and total cholesterol in serum, and improve the content of EPA, DHA, proline and cysteine in muscle, and then ameliorate muscle quality. The AMPs can improve antioxidant function, increase the content of Ig M、IL-1a、IL-1β in serum and improve immune function in Jian carp. The AMPs can up-regulate the IL-1βm RNA expression of hepatopancreas tissue in the Jian carp. The experiment studied the effects of AMPs on the relationship of the gene expression and secretion level of IGF-I and IL-1β, also analyzed the correlation between growth and immune of fish in the intervention of antimicrobial peptides. The study revealed the IGF-I is closely related with fish immunity and IL-1β is closely related with the fish growth. The data of this experiment provide reference for reasonable application of AMPs in fish farming, and also provide basic information for study on mechanism of AMPs regulate growth and immune function in fish.