Study On The Requirements Of Threonine, Leucine, Tryptophanand Valine For Juvenile Pacific White Shrimp,Litopenaeus Vannamei

A series studies were conducted to determine the threonine, leucine, tryptophan, andvaline requirements of juvenile Pacific white shrimp Litopenaeus vannamei, and evaluatedthe effect on growth performance, feed efficiency, the activities of relative enzymes for theshrimps. The results obtained can be briefly summarized as follows:1. An8-week feeding trial was conducted to determine the dietary threoninerequirement of juvenile Pacific white shrimp, Litopenaeus vannamei. Six isonitrogenousand isolipidic semipurified diets (43%crude protein and7.5%crude lipid) were formulatedto contain graded dietary threonine levels ranging from1.07%to2.30%(dry weight). In allof the diets, the nitrogen content of the amino acids was kept the same by replacingthreonine with a non-essential amino acid mixture. Each diet was randomly assigned totriplicate groups of40juvenile shrimp (approximately0.53g) that were fed4times dailyto apparent satiation. The results indicated that significant difference was observed in theweight gain among all treatments. Maximum weight gain was obtained at1.67%dietarythreonine; however, weight gain did not significantly increase with further dietarythreonine increases. There were no significant different survival of the shrimps among alltreatments. Feed efficiency（FE）, protein efficiency ratio (PER) and protein productivevaluesb(PPV) were also significantly influenced by the dietary threonine levels, and thetrends were similar to those of growth performance. There were no significant differencesin dry matter, crude protein, crude lipid or ash content in the whole body and musclecomposition among all treatments.Superoxide dismutase(SOD),Aspartate aminotransferase(AST), alanine aminotransferase (ALT),and phenoloxidase(PO) activities in hemolymphwere significantly affected by dietary threonine levels. Shrimp fed the diet containing2.30%threonine had higher AST and ALT values than those fed the other diets; however,the highest SOD and PO activities were observed at2.05%dietary threonine. The optimaldietary threonine requirement, estimated by a broken-line model based on SGR, was1.51%of the dry diet (corresponding to3.53%of dietary protein on a dry-weight basis).2. Six isonitrogenous and isolipidic practical diets (43.0%crude protein and7.0%crude lipid) were formulated to determine the dietary leucine requirement of juvenilePacific white shrimp, Litopenaeus vannamei. The six diet contain graded dietary leucine levels ranging from2.26%to3.0%(dry weight). Each diet was randomly assigned totriplicate groups of40juvenile shrimp (0.53±0.00g) that were fed4times daily toapparent satiation. The results indicated that significant difference was observed in thegrowth performance and feed utilization by the dietary leucine level. Maximum WG, SGRand PER occurred at2.48%dietary leucine, while higher dietary leucine did not obtainhigher growth or feed efficiency. There were no significant differences in dry matter,crude protein, crude lipid or ash content in the whole body and muscle composition.Superoxide dismutase (SOD),aspartate aminotransferase (AST), alanine aminotransferase(ALT) and phenoloxidase (PO) activities in hemolymph were significantly affected bydietary leucine levels, alanine aminotransferase (ALT) activities in muscle also wassignificantly affected by dietary leucine levels. There were no significant different survivalof the shrimps among all treatments. The optimal dietary leucine requirement, estimated bya broken-line model based on WG, was2.46%of the dry diet (corresponding to5.66%ofdietary protein on a dry-weight basis).3. This study was conducted to quantify the dietary tryptophan requirement ofjuvenile Pacific white shrimp. Diets containing fish meal and soybean meal as sources ofintact protein supplemented with CAA, Amino acid test diets (41%crude protein, and7.8%crude lipid) with six graded levels of tryptophan (0.21-0.45%of dry diet) were formulated.Shrimp with an initial weight of0.31±0.00g were fed to satiation with one of six diets for7weeks. The results indicated that there were significantly differences in growthperformance and feed utilization by the dietary tryptophan level. Shrimps fed the diet oflowest tryptophan had significantly lowest growth performance and feed efficiency，Maximum weight gain (WG),SGR,FE and PPVwas obtained in the shrimp fed the diet of0.28%tryptophan diet, but with the decrease or increase of dietary tryptophan levels, theWG, SGR and PER decreased. There were no significant differences in dry matter, crudeprotein, crude lipid or ash content in the whole body and muscle composition. Aspartateaminotransferase (AST), alanine aminotransferase(ALT), superoxide dismutase (SOD)activities in hemolymph were significantly affected by dietary tryptophan levels, Aspartateaminotransferase (AST), superoxide dismutase (SOD) and alkaline phosphatase (AKP)activities in hepatopancreas also was significantly affected by dietary tryptophan levels.The optimal dietary tryptophan requirement, estimated by a broken-line model based onSGR, was0.28%of the dry diet (corresponding to0.68%of dietary protein on adry-weight basis).4. An49days growth experiment was conducted to determine dietary valinerequirement for juvenile Pacific white shrimp with an initial average body weight of0.31g. Six isonitrogenous and isoenergetic isolipidic diets (crude protein41.46%, and8.1%crudelipid) and were formulated with fish meal and soybean meal as intact protein source. CAAmixtures were added to obtain six levels of dietary valine from1.56to1.96%dry diet.Each diet was randomly assigned to triplicate groups of40juvenile shrimp that were fed4times daily to apparent satiation. The results indicated that the dietary valine level weresignificantly differences in growth performance and feed utilization. Maximum weightgain was obtained at1.82%dietary valine; however, weight gain did not significantlyincrease with further dietary valine increases.SGR FE,PER and PPV were alsosignificantly influenced by the dietary valine levels, and the trends were similar to those ofgrowth performance. The crude protein of whole body and muscle were significantlyaffected by the valine level.Superoxide dismutase(SOD), Aspartate aminotransferase(AST),alanine aminotransferase(ALT) activities in hemolymph, the muscle Aspartateaminotransferase(AST), alanine aminotransferase(ALT) and alkaline phosphatase (AKP)activities in hepatopancreas were significantly affected by dietary valine levels.Broken-line regression analysis of WG in related to dietary valine showed that optimaldietary valine requirement for maximum growth of Litopenaeus vannamei was1.79%drydiet (4.33%of dietary protein).