| In the study, nine experimental diets were prepared to contain38%,45%and52%levels, atwhich protein level contain10%,20%and30%three starch levels were formulated, i.e. D1(38P/10S), D2(38P/20S), D3(38P/30S), D4(45P/10S), D5(45P/20S), D6(45P/30S), D7(52P/10S), D8(52P/20S) and D9(52P/30S). The grouper juventiles with an initial average bodyweight of6.74g were randomly divided into nine groups with triplicate tanks of20fish each. Fishin each group were fed one of the diets twice per day and fed to apparent satiation during feedingtrial lasted for56days.The values of weight gain and specific growth rates were highest in group D7, andsignificantly higher than groups D1, D2, D3, D4and D9(P<0.05), but no significant differencesthan groups D5, D6and D8(P>0.05). The values of weight gain and specific growth rates were nosignificant differences between high-protein and moderate-pritein groups (P>0.05), but both ofthem were significantly higher than low-pritein group (P<0.05); The weight gain and specificgrowth rates in high-starch group was no significant differences compared moderate-starch andlow-starch groups (P>0.05), but the moderate-starch group was significantly higher than low-starchgroup (P<0.05). The daily feeding intake rate and feed conversion rate exhibited significantlydecreased with dietary protein and starch levels improving (P<0.05), however, the proteinefficiency rate was significantly increased (P<0.05). The hepatosomatic index, viscerasomatic indexand condition factor did not differ across treatments (P>0.05). The apparent digestibility coefficientof crude protein was significantly decreased with dietary protein level improving (P<0.05), but wasnot affected by dietary starch level; The apparent digestibility coefficient of starch exhibitedsignificantly decreased with dietary protein and starch levels improving (P<0.05); However, theapparent digestibility coefficient of crude lipid did not differ across treatments (P>0.05). Thewhole-body lipid and protein contents exhibited significantly increased with dietary protein andstarch levels improving (P<0.05), meanwhile, the moisture was significantly decreased (P<0.05);However, the whole-body ash did not differ across treatments (P>0.05).In terms of blood biochemical components, the glucose, triglycerides and total amino acidcontents exhibited significantly increased with dietary protein and starch levels improving (P<0.05);The blood urea nitrogen contents was significantly increased by improving dietary protein level,however, significantly decreased was found by improving dietary starch level (P<0.05); The totalcholesterol, high density lipoprotein cholesterol and low density lipoprotein cholesterol contents did not differ across the treatments (P>0.05). The contents of hepatic glycogen and liver lipid exhibitedsignificantly increased with dietary protein and starch levels improving (P<0.05), but the muscleglycogen was no significantly differences(P>0.05). The liver activity of glucosekinase,pyruvatekinase, phosphoenolpyruvate carboxykinase and glucose-6-phosphate dehydrogenase werenot effected by improving dietary protein level, however，the activity of glucose-6-phosphatase wassignificantly decreased and the malic enzyme was significantly increased (P<0.05); When thedietary starch level was improving, the activity of glucosekinase, pyruvatekinase,Glucose-6-phosphate dehydrogenase and malic enzyme exhibited significantly increased (P<0.05),however, the activity of Phosphoenolpyruvate carboxykinase and glucose-6-phosphatase wassignificantly decreased (P<0.05); The activity of phosphofructokinase did not differ across thetreatments (P>0.05). The liver activity of hepatic lipase, lipoprotein lipase, fatty acid synthetase,glutamic-pyruvic transaminase and glutamic-oxalacetic transaminase exhibited significantlyincreased with dietary protein and starch levels improving (P<0.05), but the activity of glutamatedehydrogenase was significantly decreased (P>0.05). The serum contents of insulin and insulin-likegrowth factor was not effected by dietary protein level, but exhibited significantly increased firstand after that it has an approximate constant; The serum contents of glucagon and growth hormoneexhibited significantly decreased with dietary protein and starch levels improving (P<0.05), but thetriiodothyronine, thyroxine and cortisol contents was significantly increased (P<0.05).The results indicate that different dietary protein and starch levels exhibited significantinteraction on growth performance and the starch level of20%may show the saving protein effect.The appropriate combination of protein and starch levels was45P/20S which protein to energy ratiowas25.25mg/KJ in dietary. |
PDF Full Text Request