Effects Of Dietary Carbohydrate,Protein And Lipid Levels On Growth And Feed Utilization Of Giant Grouper Epinephelus Lanceolatus Larvae

1. A consecutive8-week growth trial was undertaken to determine effects of dietary protein and lipid levels on growth performance, feed utilization and body composition of giant grouper Epinephelus lanceolatus larvae. In the trial, six approximately isoenergetic experimental diets were formulated to contain49%(P49) or44%(P44) crude protein (CP) levels (dry-matter basis), and at each dietary CP level, three crude lipid (CL) levels of22%,20%and17.5%were designed. These treatments were abbreviated as P49/L22, P49/L20, P49/L17.5, P44/L22, P44/L20and P44/L17.5, respectively. Groups of50experimental giant grouper larvae (average initial weight of0.72g/fish) in the trial were stocked in floating cages (L120cm×W70cm×H50cm) placed in indoor6-m3concrete ponds running with following sea water (salinity:33.1g/L). Triplicates of fish were fed each dietary treatment three times daily to apparent satiation. Water quality was monitored daily.Weight gain (WG) of fish fed the diet with49%crude protein was significantly higher (P<0.05) than that of fish fed the diet with44%CP. Reducing dietary crude lipid from22%to17.5%had no significant influences (P>0.05) on growth performance of giant grouper larvae. Fish fed the P49diet exhibited significantly lower feed conversion ratio (FCR) than fish fed the P44diet. Protein productive value (PPV) was decreased when dietary CP was improved from44%to49%. No significant differences in values of PPV or FCR were observed among fish fed dietary CL varying at17.5-22%. Feed intake (FI) as well as survival ratio was not affected by different experimental treatments. Dietary CP levels displayed no significant effects on hepatosomatic index (HSI), while this value decreased with dietary CL increasing. Condition factor (CF) of experimental fish kept relatively unvaried in this study. Intraperitoneal fat (IPF) ratios of fish fed the P49diet were significantly lower than fish fed the P44diet. Whole-body lipid content was improved with dietary CL increasing but less affected by dietary CP levels. Muscle protein as well as lipid contents were not influenced by dietary lipids. Liver protein and lipid contents had a decreasing trend with dietary lipid decreasing. Liver glycogen content in fish fed22%or20%lipid was significantly lower than fish fed17.5%lipid.2. Carbohydrate is one of the three major nutrients in aquatic feeds. A growth trial was undertaken to study utilization of different dietary digestible carbohydrate sources by the grouper Epinephelus lanceolatus larvea. Five isonitrogous (crude protein:45%of dry matter) and isolipidic (crude lipid:22%of dry matter) experimental diets included a carbohydrate-free control diet and four carbohydrate contained diets were formulated in this experiment. The inclusion level of dietary carbohydrate in all experimental groups was8%. Each diet was fed to triplicate groups of fish (initial body weight:0.44g) stocked in6m3-volume pools at a density of60fish per cement pool. Fish were hand-fed their randomly designed experimental diets to satiation three times a day for40days. Results showed that there were no significant (p>0.05) differences in values of weight gain among all experimental treatments. Specific growth rate (SGR) of fish fed the carbohydrate-free control diet was significantly (p<0.05) lower than that of value in other groups. Feed efficiency (FE), protein efficiency ratio (PER) and protein productive value (PPV) showed no significant (p>0.05) differences among all experimental groups. As well as whole-body, liver and muscle compositions showed marked variations among different groups. Plasma Cereal third transaminase (ALT), Albumin (ALB), Glucose, high-density lipoproteincholesterol (HDL-C), low-density lipoproteincholesterol (LDL-C) were significantly (p<0.05) affected by dietary carbohydrate sources. Fish intestinal amylase and maltase enzyme activity ware no significant (p>0.05) among all experimental groups.Generally, Epinephelus lanceolatus larvae could utilize8%dietary glucose, or maltose, or dextrin or starch at this experimental conditions.3. An8-week growth trial was undertaken to determine effects of dietary carbohydrate-to-lipid ratios on growth performance, feed utilization and body composition of giant grouper Epinephelus lanceolatus larvae. In this trial, five approximately isoenergetic and isonitrogenous (49%CP) experimental diets were formulated to contain different carbohydrate (CHO)/lipid (L) ratios as followed:CHO0/L22, CHO4.95/L19.8, CHO9.9/L17.6, CHO14.85/L15.4and CHO19.8/L13.2(dry-matter basis), respectively. Groups of41fish larvae (average initial weight of0.397g/fish) were stocked in floating cages (L120cmxW70cmxH50cm) placed in indoor6-m3concrete ponds running with following sea water (salinity:33.1g/L). Triplicates of fish were fed each dietary treatment three times daily to apparent satiation. Water quality was monitored daily.CHO/L ratios varying at CHO0/L22, CHO4.95/L19.8, CHO9.9/L17.6and CHO14.85/L15.4did not significantly affect values of FCR but FCR of fish fed CHO19.8/L13.2was significantly lower than that of fish fed other experimental diets. Protein productive value (PPV) was decreased as dietary CHO/L ratio was increased to CHO19.8/L13.2. No significant differences in values of PPV were observed among fish fed CHO0/L22,CHO4.95/L19.8,CHO9.9/L17.6and CHO14.85/L15.4. Feed intake(FI) as well as survival ratio were not affected by different experimental treatments. IPF ratios of fish fed CHO0/L22,CHO4.95/L19.8were significantly higher compared to fish fed CHO9.9/L17.6,CHO14.85/L15.4and CHO19.8/L13.2. Whole-body moisture and protein maintained relatively steady among all dietary treatments except that, fish fed CHO19.8/L13.2had significantly lower whole-body protein compared to fish fed CHO14.85/L15.4,CH09.9/L17.6,CH04.95/L19.8and CHO0/L22. Liver protein and lipid contents had a decreasing trend with the increasing CHO/L ratio. Liver glycogen content in fish fed CHO0/L22or CHO4.95/L19.8was significantly lower than fish fed CHO9.9/L17.6,CHO14.85/L15.4or CHO19.8/L13.2.4. The distributions of glucose transporters genes (GLUTs) in the liver, muscle and intestine of the grouper Epinephelus lanceolatus larvae were studied. Resulted showed that Glut4was expressed in the muscle tissue, and Glutl was expressed in the liver, muscle and intestine tissue.