The Study On Protein Nutrition Physiology Of Turbot, Scophthalmus Maximus Linnaeus And Half-Smooth Tongue-Sole, Cynoglossus Semilaevis Gunther

Feeding trials were conducted in indoor culture system to investigate the effects of protein level, protein to energy ratios, soy protein concentrate (SPC) and corn gluten meal (CGM) levels partially replacing fish meal (FM),supplemental taurine in diets on feed intake, growth and feed utilization of turbot (Scophthalmus maximus Linnaeus).Also, effects of protein to energy ratios on growth performance of Half-Smooth Tongue-Sole, Cynoglossus semilaevis Gunther was conducted. Results of the study are presented as follows:â… .Specific growth rate (SGR) of Turbot increased with increasing dietary protein level from 47.22% to 50.99% and then plateaued above these levels (P<0.05). Fish fed the diets with 63.62% protein had the highest SGR and fish fed the diets with 59.33% protein had the highest FER. Feed intake (FI) and protein efficiency ratio (PER) showed no significant difference among dietary treatments (P>0.05). Carcass moistrue, protein, lipid and ash contents were generally not affected by diets (P>0.05). Dietary protein level had no significant effect on serum ammonia (P>0.05), while serum urea_increased with increasing dietary protein level significantly (P<0.05).Based on broken-line regression analysis of SGR the optimal dietary protein requirement for Turbot was determined to be around 57.0%.â…¡.Results of three feeding trails with different size of experimental fish suggested that the growth performance and feed conversion ratio of Turbot generally were improved with increasing dietary protein (P<0.05) at each lipid. Fish fed the diets with 55% protein and 12% lipid (P/E ratio of 26.37 mg protein kJ-1)had the highest specific growth rates (SGR), feed efficiency ratio (FER), protein productive value (PPV) and energy retention (ER).However, fish fed the diet with 45% protein and 16% lipid showed comparable protein efficiency ratio (PER) and PPV, and higher values than fish fed the diet with 45% or 50% protein with 12% lipid, indicating a protein sparing effect of lipid. Both carcass lipid and energy content were positively correlated with dietary energy level except in adult stage fish. Carcass protein and ash contents were generally not affected by dietary treatments. Dietary P/E ratios had no significant effect on condition factor (CF), viscerosomatic index (VSI), while hepatosomatic index (HSI) was significantly affected by dietary P/E ratios (P<0.05).In adult stage, hepatic glycogen of fish fed 16% lipid was significantly lower than that of fish fed 12% lipid.The hepatic activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lipid of liver, serum triglycerides, serum urea and total cholesterol concentration in serum of middle and adult fish were not significantly influenced by dietary P/E ratios. While in juvenile stage, the hepatic activity of ALT and AST of fish fed 45% or 55% protein with 12% lipid were significantly higher than that of fish fed other diets (P<0.05); lipid of liver were significantly improved in the group of fish fed 45 or 50% protein at 16% lipid (P<0.05); and serum triglycerides, serum urea and total cholesterol concentration in serum were increased with increasing dietary protein or lipid levels (P<0.05).â…¢.Feed intake (FI) (P<0.001)and specific growth rate (SGR) (P<0.001)decreased linearly with increasing dietary SPC levels. There were no significant differences (P>0.05) in feed efficiency ratio (FER) and protein efficiency ratio (PER) among fish fed diets with 0%-37.0% SPC (diet1-4).However, fish fed the diet with 49.5% SPC (diet5) had significantly lower FER and PER. Apparent digestibility coefficients of dry matter and crude protein of the fish were not significantly (P>0.05) affected by dietary treatments. Dietary SPC level had no significant effect on condition factor (CF), viscerosomatic index (VSI), carcass composition, serum triglycerides, serum urea and amino acids composition except glycin. Total cholesterol concentration in serum of fish was significantly reduced with increasing dietary SPC level (P<0.01).â…£.Feed intake (FI), specific growth rate (SGR), feed efficiency ratio (FER) and protein efficiency ratio (PER) were decreased significantly with the increase of CGM in diets. There were no significant differences (P>0.05) in growth performance between fish fed diet with 0% and 12% CGM.However, fish fed diet containing above 25% CGM had significantly lower (P<0.05) growth than those fed diet with 0% and 12% CGM.Supplementation with CAA improved FI, SGR, PER of fish, but no significant difference was observed. PER of fish was significantly improved by supplemented with CAA (P>0.05).Survival ranged from 92.59% to 98.15% and no significant difference was observed.(P>0.05). Carcass composition, serum triglycerides and serum urea of the fish were not significantly (P>0.05)affected by dietary treatments. Total cholesterol concentration in serum of fish was significantly reduced with increasing dietary CGM level (P<0.05).V.Feed intake (FI), the specific growth rate (SGR), feed efficiency ratio (FER), protein effciency ratio (PER), hepatosomatic index (HSI), serum total cholesterol concentration and serum triglycerides in fish fed FM-based diets were significantly higher than those in fish fed SPC-based diets (P<0.05).In addition, carcass protein and lipid contents of fish fed SPC-based diets were significantly lower than those in fish fed FM-based diets (P<0.001).Survival,FI,final weight, serum triglycerides, condition factor (CF) and viscerosomatic index (VSI) were not significantly different among fish fed graded levels of taurine levels (P>0.05). While SGR, FER, PER, serum total cholesterol concentration and carcass protein content were significantly improved with increasing dietary taurine levels (P<0.05).VI.The growth of Cynoglossus semilaevis Gunther was significantly affected by dietary P/E ratio (P<0.05). Fish fed the diets with 55% protein(12% lipid, P/E ratio of 26.37mg protein kJ-1) had the highest specific growth rates (SGR), feed efficiency ratio (FER), protein productive value (PPV) and energy retention (ER). SGR significantly increased with increasing dietary protein from 45% to 55% irrespective of dietary lipid (P<0.05). However, at each protein level,fish fed the diet with 16% lipid showed significant higher FI (P<0.001)and lower SGR, FER, PER, PPV, ER (P<0.001) and HSI (P<0.01)than fish fed the diet with 12% lipid. No significant differences in survival were found among dietary treatments. Carcass protein content was significantly reduced by diet with 45% protein and 16% lipid and inversely correlated with carcass moisture content. Carcass lipid and ash contents were generally not significantly affected by dietary treatments. Dietary P/E ratios had no significant effect on condition factor (CF), viscerosomatic index (VSI), lipid of liver, serum urea and ammonia. Hepatic glycogen of fish fed 16% lipid was significantly lower than that of fish fed 12% lipid (P<0.01),while the hepatic activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly higher(P<0.001).These results suggest that the diet containing 55% protein and 12% lipid with P/E of 26.37 mg protein kJ-1 is optimal for Cynoglossus semilaevis Gunther and increase of dietary lipid level has no efficient protein-sparing effect.