Effects Of Altering Dietary Protein And Lipid Contents In The Evening Feeding On Growth, Feed Utilization Of Orange-spotted Grouper(Epinephelusbleekeri) And(Epinephelus Lanceolatus×Epinephelus Fuscoguttatuss)

1. An8-week growth trial was undertaken to compare effects of different feeding regimes in which dietary protein and lipid contents were varied in the evening feeding on growth, feed utilization, immunity, plasma indices, biochemical enzyme activities and histology of orange-spotted grouper (Epinephelus coioides). In this trial, three different dietary crude protein levels [48%(HP),43%(MP),38%(LP)] and three different dietary crude lipid levels [12%(HL),10%(ML),8%(LL)] were designed to formulate five experimental diets (HP-HL, MP-HL, LP-HL, HP-ML or HP-LL). In the morning feeding, all experimental fish were fed the HP-HL diet, and in the evening feeding, the HP-HL diet was replaced with the MP-HL, LP-HL, HP-ML or HP-LL diet to form five different experimental treatments. Juvenile orange-spotted grouper (average initial weight of14.0g/fish) were stocked in500-L tanks containing sea water (30g/L) and operated as a flow-through water system. Fish in triplicate tanks were hand-fed each dietary treatment twice a day to apparent satiation for8weeks.Weight gain (WG), hepatosoomatic index (HSI), and viscerosomatic index (VSI) of orange-spotted grouper fed the HP-HL diet at p.m. showed no significant (p>0.05) differences compared to fish fed the MP-HL, LP-HL, HP-ML or HP-LL diet at p.m. Protein efficiency ratios (PER) were significantly (p<0.05) affected by different dietary lipid levels. Whole body and muscle protein, and lipid contents also significantly varied among different experimental treatments. Plasma immune indices and biochemical compositions in HP-LL group were significantly (p<0.05) lower than those of values in fish fed the HP-HL and HP-ML diets, but had no remarkable variations compared to the MP-HL and LP-HL groups. The HP-LL group had significantly (p<0.05) higher liver gluco-6-phosphate dehydrogenase (G-6-PD) activities than other groups did. The LP-LL group had significantly (p<0.05) higher liver isocitrate dehydrogenase (IDH) activities than other groups did. Hepatocytes with migration of nuclei were observed in the HP-HL group. Amount of hepatocytes nuclei did not significantly differ among the experimental groups. Fish fed the LP-HL and HP-LL diets had the most enlarged hepatocytes and apparent steatosis with intense vacuoles in the hepatocytes resembling lipids. Based on the growth results, reducing dietary protein level from48%to38%or dietary lipid level from12%to8%at the evening feeding did not negatively affect growth of orange-spotted grouper.2. An8-week growth trial was undertaken to compare effects of different feeding regimes in which dietary protein and lipid contents were varied in the morning feeding on growth, feed utilization, immunity, plasma indices, biochemical enzyme activities and histology of Epinephelus Lanceolatus×Epinephelus fuscoguttatuss. In this trial, three different dietary crude protein levels [44%(HP),38%(MP),33%(LP)] and three different dietary crude lipid levels [10%(HL),7.5%(ML),5.0%(LL)] were designed to formulate five experimental diets (HP-HL, MP-HL, LP-HL, HP-ML or HP-LL). In the evening feeding, all experimental fish were fed the HP-HL diet, and in the morning feeding, the HP-HL diet was replaced with the MP-HL, LP-HL, HP-ML or HP-LL diet to form five different experimental treatments. Juvenile orange-spotted grouper (average initial weight of53.12±2.85g) were stocked in cages (1.8m:0.8m:0.6m) containing sea water (30g/L) and operated as a flow-through water system. Fish in triplicate tanks were hand-fed each dietary treatment twice a day to apparent satiation for8weeks.Feed intake (FI), feed conversion ratio (FCR), protein intake (PI), survival (SV), as well as viscerosomatic index (VST) and Intraperitoneal fat (IPF) of Epinephelus Lanceolatus×Epinephelus fuscoguttatuss.fed the HP-HL diet at a.m. showed no significant (p>0.05) differences compared to fish fed the MP-HL, LP-HL, HP-ML or HP-LL diet at a.m. The fish fed HP-HL diet at a.m. had the best value of weight gain (WG), and the LP-HL and HP-LL groups had the lowest, but there had no significantly variations among experiment treatments (p>0.05). Specific growth rate (SGR) and feed efficiency (FE) were significantly (p<0.05) affected by different dietary protein levels in the morning feeding. Protein efficiency ratios (PER) were significantly (p<0.05) affected by different dietary lipid levels. The fish fed HP-HL diet at a.m. had the lowest value of hepatosomatic index (HSI) and condition factor (CF). Whole body, muscle and hepatic protein and lipid contents also varied remarkably among experimental treatments (p>0.05). The activities of trypsin were significantly (p<0.05) affected by different dietary lipid levels. The HP-LL group had significantly (p<0.05) higher liver isocitrate dehydrogenase (IDH) activities than other groups did. Liver gluco-6-phosphate dehydrogenase (G-6-PD) activities and malate dehydrogenase (MDH) were not significantly affected by different dietary protein and lipid levels. The goblet cells and vacuoles were significantly (p<0.05) affected by different dietary protein and lipid levels. Hepatocytes with migration of nuclei was not observed in different treatments. The hepatocytes with spherical nucleus centrally located were irregular in formation with the decrease of dietary protein level. Fish fed the LP-HL and HP-LL diets in the morning had less hepatocytes nuclei compared to the control group. Fish fed the LP-HL and HP-LL diets in the morning had the most enlarged hepatocytes and apparent steatosis with intense vacuoles in the hepatocytes resembling lipids. Gernerally, reducing dietary protein level from50%to44%or dietary lipid level from10%to7.5%at the morning feeding did not negatively affect growth of Epinephelus coioide×Epinephelus fuscoguttatuss but reducing dietary protein level from50%to38%or dietary lipid level from10%to5.0%at the morning feeding did reduce growth and physiological feature of Epinephelus LanceolatusxEpinephelus fuscoguttatuss.