Study Of Lipid Requirements Of Mirror Carp(Cyprinus Carpio L.) Juveniles At Different Temperatures

This experiment was conducted to study the effects of dietary lipid levels(5，8，11，and15%) on growth, body composition, immunity and antioxidant function, serumbiochemical indexes, digestive enzymes activities, liver free fatty acids and liverhistological structure in mirror common carp (Cyprinus specularis) juveniles atdifferent temperatures(16，23，and30℃).756mirror common carp (initial bodyweight5.51±0.05g) were randomly divided into12treatments and each treatmentincluded3replicates. The main results of the study were as follows:1. Effects of different lipid levels on growth, body composition of common carp atdifferent temperaturesThe results showed that: With the increase of temperature, the growth performanceof mirror common carp increased significantly.The growth performance of differentlipid levels were no significant difference except ratio of liver weight and body weightand ratio of viscera and body weight at different temperatures, at30℃, the ratio ofviscera and body in15%lipid group was significantly higher compared with5%fatgroup (P <0.05), the ratio of liver weight and body weight in5%fat group wassignificantly lower than that in8%and15%fat groups；the crude protein of mirror carpjuvenile fish were significantly decreased and crude fat had increasing trend with theincrease of dietary lipid levels（P<0.05）,at30℃there was significant difference；at23℃, thefree fatty acids(FFA) of liver were significantly increased with the increase ofdietary lipid level (P <0.05), at30℃,the15%lipid group were significantly higherthan other groups (P <0.05). We can conclude that the optimum dietary lipidrequirements for common carp was5%at different temperatures from the growthperformance and body composition.2. Effects of different lipid levels on serum biochemical indexes, and liver/kidneyhistological structure of common carp at different temperaturesSerum biochemical indicators were affected by temperatures. At16℃, thetotalprotein(TP), globuim(GLB), glutamic-pyruvic transaminase(GPT), glutamic oxalic- etic transaminease（GOT）,trig-lyceride（TG）,total cholesterol(CHOL) and bloodglucose（GLU）concentration of serum were significantly increased with the increase ofdietary lipid levels (P <0.05)，and ALT、AST、TG、CHOL concentration of serum in15%lipid group were significantly higher than other groups. At23℃, the TP,albumin（ALB）,GLB,ALT,AST, total bilirubin（TBIL）and indirect bilirubin（IBIL）concentration of serum were significantly increased with the increase of dietary lipidlevels (P <0.05)；At30℃onlyALT and AST concentration of serum increased with theincrease of dietary lipid level，and the ALT concentration in11%and15%lipid groupsignificantly higher than that in the5%and8%groups（P<0.05），AST concentration in15%lipid group significantly higher than that in the5%and8%groups（P<0.05）;Otherindicators were no significantly difference at different lipid levels. Tissue sectionanalysis showed that the mirror carp liver cells had appeared nutritional fatty liversymptoms: irregular, vacuolated, the nucleus offset and swelling with increasing lipidlevels at different temperatures. It was easy to lead to the formation of nutritional fattyliver and had an obvious impact on liver tissue structure when fed fat levels over8%at16℃andover11%at23℃,30℃. Theserum biochemical indexes and tissue sectionanalysis indicated that it was easy lead to the change of biochemical indexes andliver/kidney histological structure with the increase of lipid levels and recommendedthat lipid levels should not exceed8%.3. Effects of different lipid levels on immunity and immune response and digestiveenzymes activities of common carp at different temperaturesThe results showed that: At16℃, the superoxide dismutase (SOD) and catalase(CAT) activity of liver were significantly decreased with the increase of dietary lipidlevels (P <0.05),5%and8%lipid group was significantly higher than the11%and5%group (P <0.05), the liver malondialdehyde (MDA) concentration of15%lipid groupwas significantly higher than that of the8%group（P<0.05）, the spleen MDAconcentration of5%and8%lipid group was significantly higher than that in the15%group（P<0.05）.At23℃, the SOD and lysozyme (LYZ) activity of liver were increasedfirst and then showed a declining tendency thereafter with the decrease dietary lipidlevel, the SOD activities of liver5%and15%lipid group was significantly lower thanthat in the8%and11%group (P <0.05), the LYZ activities of liver15%lipid groupsignificantly lower than8%group（P<0.05）, the MDA of liver and the SOD、MDA ofspleen were significantly increased with the increase of dietary lipid level（sP<0.05）. At30℃, the LYZ activity of liver15%lipid group were significantly lower than other groups, serum IgM concentration in5%lipid group significantly lower than that in the15%group（P<0.05）. Immunity and antioxidant function were more affected bytemperature at different lipid levels （P<0.05）. The lipase activity decreased with theincrease of dietary lipid level,but this phenomenon was less obvious at30℃;Proteaseand amylase activity did not show the regularity corresponding to the difference with fatlevels. According to immune indexes, it was concluded that lipid level of5%to8%tomaintain a normal immune system.In summary, under the experimental conditions the optimal fat demand ofMatsuura mirror carp juvenile were as follows:5%to8%in16°C and8%to11%in23°C and30°C.