Studies On Requirements Of Leucine, Isoleucine And Tryptophan In Diets Of Japanese Seabass, Lateolabrax Maculatus

Feeding trials were conducted to investigate the optimum requirement of dietary leucine, isoleucine and tryptophan for Japanese seabass. The results of the present study were presented as follows:1. The present study was conducted to estimate the quantitative requirement of leucine in Japanese seabass (Lateolabrax maculatus) [initial body weight: (167.82±2.16) g] by feeding six isonitrogenous and isoenergetic practical diets containing graded levels of leucine 1.24%,1.85%,2.43%,3.05%,3.64%and 4.22%(dry weight), respectively, named dietl-diet6. After a 10-week growth trial, results showed that weight gain rate (WGR), specific growth ratio (SGR) and feed efficiency (FE) were significantly influenced by dietary treatments (P<0.05). The values increased first, and then declined as the dietary leucine levels increased. The highest values of these three parameters were 135.09%,1.36%/d and 0.83in fish fed the diet with 3.05%dietary leucine of dry matter, respectively. Survival rate (SR), viscerosomatic index (VSI), hepatosomatic index (HSI), condition factor (CF), body composition and the essential amino acids of muscle were not significantly influenced by dietary leucine level (P>0.05). Dietary leucine significantly affected the activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) in livers (P<0.05). The level of triglicerid (TG) in serum was significantly affected by dietary leucine levels (P<0.05). Fish fed the diet with 3.05% leucine had the highest TG value. Activities if GOT and GPT and total cholesterol (TC) levels in serum were not significantly affected by dietary treatments(P>0.05). On basis of WGR and FE, using the second-order regression analysis, dietary leucine requirement of Japanese seabass in the middle growing stage were estimated to be 2.76% and 2.80% dry diet (6.54% and 6.63% dietary protein), respectively.2. The present study was conducted to estimate the quantitative requirement of isoleucine in Japanese seabass [initial body weight:(159.33±1.20)g] by feeding six isonitrogenous and isoenergetic practical diets containing graded levels of isoleucine 0.72%,1.11%,1.53%,1.93%,2.31% and 2.72%(dry weight), respectively, named dietl-diet6. After a 10-week growth trial, results showed that weight gain rate (WGR), feed efficiency (FE) and protein retention (PR) were significantly influenced by dietary (P<0.05). The values increased first, and then declined as the dietary isoleucine levels increased. The highest values of these three parameters were 108.55%,0.89 and 37.57%in fish fed the diet with 1.93% dry matter of dietary isoleucine, respectively. Survival rate (SR), feed intake (FI), viscerosomatic index (VSI), hepatosomatic index (HSI), condition factor (CF), body composition and the essential amino acids of muscle were not significantly influenced by dietary isoleucine level (P>0.05). Dietary isoleucine significantly affected the activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) in livers (P<0.05). The serum triglicerid (TG) was significantly affected by dietary isoleucine levels (P<0.05). Fish fed the diet with 1.93%isoleucine had the highest TG value. GOT and GPT activities and total cholesterol (TC) levels in serum were not significantly affected (P>0.05). In conclusion, dietary appropriate isoleucine level can improve the growth of the seabass. On basis of WGR and PR, using the second-order regression analysis, dietary isoleucine requirement of Japanese seabass in the middle growing stage were estimated to be 1.88% and 1.84% dry diet (4.41% and 4.32% dietary protein), respectively.3. The present study was conducted to estimate the quantitative requirement of L-tryptophan in Japanese seabass [initial body weight:(159.90±1.89) g] by feeding six isonitrogenous and isoenergetic practical diets containing graded levels of tryptophan 0.14%,0.25%,0.32%,0.39%,0.45% and 0.57%(dry weight), respectively, named dietl-diet6. After a 10-week growth trial,results showed that weight gain rate (WGR), specific growth ratio (SGR) and feed efficiency (FE) were significantly influenced by dietary (P<0.05). The values increased first, and then declined as the dietary tryptophan levels increased. The highest values of these three parameters were 154.00%,].48%/d and 0.81 in fish fed the diet with 0.39% dry matter of dietary tryptophan, respectively.Survival rate (SR)was significantly influenced by dietary tryptophanlevel (.P>0.05).The values increased first, and then remained unchanged as the dietary tryptophan levels increased.Viscerosomatic index (VSI), hepatosomatic index (HSI), condition factor (CF), body composition and the essential amino acids of muscle were not significantly influenced by dietary tryptophanlevel (F>0.05). Dietary tryptophan significantly affected the activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) in livers (P<0.05). GOT and GPT activitiesand levels of triglicerid (TG) and total cholesterol (TC) in serum were not significantly affected (P>0.05). In conclusion, dietary appropriate tryptophan level can improve the growth of the seabass. On basis of WGR and FE, using the second-order regression analysis, dietary tryptophan requirement of Japanese seabass in the middle growing stage were estimated to be 0.40% and 0.39% dry diet (0.92% and 0.90% dietary protein), respectively.