Study On The Requirements Of Protein, Arginine,Lysine And Methionine For Juvenile Swimming Crab, Portunustritu Berculatus

In the present study, feeding trials were conducted to evaluate the requirements of protein,arginine, lysine and methionine for juvenile swimming crab, Portunus trituberculatus, andevaluated the effect on growth performance, feed efficiency, whole-body composition, amino acidcomposition of the muscles, the activities of amino acids metabolic enzymes for the crabs. Theresults can be briefly summarized as follows:1.An8-week feeding trial was conducted to determine the optimal dietary proteinrequirements for juvenile swimming crabs（Portunus trituberculatus）reared in cement pools. Sixiso-energetic and iso-lipidic experimental diets were formulated to contain graded levels of protein,which dietary protein levels were31.6,36.5,41.7,45.6,50.2and55.8%of the dry matter,respectively. Each diet was randomly assigned to triplicate groups of60juvenile swimming crabs(approximately2.50±0.08g) that were stocked in rectangle plASTic baskets. The results indicatedthat dietary protein had a significant effect on weight gain, specific growth rate, protein productivevalue, feed conversion ratio and protein effifiency ratio, and maximal weight gain and specificgrowth rate were obtained at50.2%dietary protein. No mortality was found among all treatmens.Dietary protein had a significant effect on whole-body crude protein, total lipid, moisture contentand on muscle amino acid profile; and a positive correlation was observed between EAAsconcentrations in muscle and dietary protein levels, however, there were no significant differencein ash content of whole body. The optimal dietary protein requirement, estimated by two slopebroken-line model based on specific growth rate against dietary protein levels, was51.5%of thedry matter for juvenile swimming crabs.2.An8-week feeding trial was conducted to determine the optimal dietary argininerequirements for juvenile swimming crabs（Portunus trituberculatus）reared in cement pools. Sixiso-nitrogenous and iso-lipidic experimental diets (49.5%crude protein and7.5%crude lipid) wereformulated to contain graded levels of arginine, which dietary arginine levels were1.59%、1.91%、2.26%、2.74%、3.04%and3.30%of the dry matter, respectively. Each diet was randomly assigned to triplicate groups of60juvenile swimming crabs (approximately4.72±0.12g) that werestocked in rectangle plASTic baskets. The results indicated that dietary arginine had a significanteffect on weight gain(WG), specific growth rate(SGR), protein productive value(PPV), feedefficiency(FE) and protein effifiency ratio(PER)(p<0.05). WG and SGR were increasedsignificantly with the dietary arginine increase from1.59%to2.74%, but dietary arginine from2.74%to3.04%, WG and SGR did not increase significantly(p>0.05). No mortality was foundamong all treatmens. There were no significant differences in the compositions of whole body andmuscle (moisture, crude protein, crude lipid and ash)(p>0.05); and there were no significantdifferences in the amino acid composition of the muscles (p>0.05) except for the arginine andΣEAA. The arginine and ΣEAA of muscles fed1.59%arginine diet was higher than that of othertreatments. Aspartate aminotransferase(AST) and alanine aminotransferase(ALT) in haemolymphwere significantly affected by dietary argnine levels(p<0.05). The optimal dietary argininerequirement, estimated by two slope broken-line model based on specific growth rate againstdietary arginine levels, was2.80%of the dry matter (5.66%dietary protein) for juvenile swimmingcrabs.3.An8-week feeding trial was conducted to determine the optimal dietary lysine requirementsfor juvenile swimming crabs （Portunus trituberculatus） reared in cement pools. Sixiso-nitrogenous and iso-lipidic experimental diets (49.5%crude protein and7.5%crude lipid) wereformulated to contain graded levels of arginine, which dietary arginine levels were1.58%、1.89%、2.15%、2.41%、2.67%and2.90%of the dry matter, respectively. Each diet was randomlyassigned to triplicate groups of60juvenile swimming crabs (approximately7.86±0.16g) that werestocked in rectangle plASTic baskets. The results indicated that dietary lysine had a significanteffect on weight gain(WG), specific growth rate(SGR), protein productive value(PPV), feedefficiency(FE) and protein effifiency ratio(PER)(p<0.05). WG and SGR were increasedsignificantly with the dietary arginine increase from1.58%to2.41%, and the decreased with thedietary lysine from2.41%to2.90%. No mortality was found among all treatmens. There were nosignificant differences in the compositions of whole body and muscle (moisture, crude protein,crude lipid and ash)(p>0.05)except for the crude protein of whole body. The crude protein ofwhole body fed2.41%lysine diet was higher than that of other treatments; and there were nosignificant differences in the amino acid composition of the muscles (p>0.05). Aspartateaminotransferase(AST) in haemolymph were significantly affected by dietary argninelevels(p<0.05), but alanine aminotransferase(ALT) showed no significant differences (p>0.05). Theoptimal dietary lysine requirement, estimated by two slope broken-line model based on specificgrowth rate against dietary lysine levels, was2.41%of the dry matter (4,87%dietary protein) for juvenile swimming crabs.4.An8-week feeding trial was conducted to determine the optimal dietary methioninerequirements for juvenile swimming crabs（Portunus trituberculatus）reared in cement pools. Sixiso-nitrogenous and iso-lipidic experimental diets (49.5%crude protein and7.5%crude lipid) wereformulated to contain graded levels of methionine, which dietary arginine levels were0.61%、0.77%、0.97%、1.18%、1.44%and1.64%of the dry matter, respectively. Each diet was randomlyassigned to triplicate groups of60juvenile swimming crabs (approximately11.27±0.13g) that werestocked in rectangle plASTic baskets. The results indicated that dietary methionine had asignificant effect on weight gain(WG), specific growth rate(SGR), protein productive value(PPV),feed efficiency(FE) and protein effifiency ratio(PER)(p<0.05). WG and SGR were increasedsignificantly with the dietary methionine increase from0.61%to0.97%, but dietary methioninefrom0.97%to1.44%, WG and SGR did not increase significantly(p>0.05). No mortality wasfound among all treatmens. There were no significant differences in the compositions of wholebody and muscle (moisture, crude protein, crude lipid and ash)(p>0.05); and there were nosignificant differences in the amino acid composition of the muscles (p>0.05). The optimal dietaryarginine requirement, estimated by two slope broken-line model based on specific growth rateagainst dietary methionine levels, was1.07%of the dry matter (2.16%dietary protein) for juvenileswimming crabs.