An 8-week feeding experiment was conducted to evaluate the dietary leucine requirement of ¢ngerling Indian major carp, Labeo rohita (3.50 AE 0.04 cm; 0.40 AE 0.02 g) using amino acid test diets (40% crude protein; 17.90 kJ g À1 gross energy) containing casein and gelatin as intact protein sources and L-crystalline amino acids. Growth performance and biochemical parameters were assessed by feeding six amino acid test diets supplemented with graded concentrations of leucine (0.75, 1.0, 1.25, 1.50, 1.75 and 2.0 g per 100 g) to triplicate groups of ¢ngerlings to apparent satiation divided over two feedings at 07:00 and 17:30 hours. Performance of the ¢sh was evaluated on the basis of live weight gain, feed conversion ratio (FCR), protein e⁄ciency ratio (PER) and body protein deposition (BPD) data. Maximum live weight gain (315%), best FCR (1.35), highest PER (1.86) and BPD (33.9) were recorded at 1.50 g per 100 g dietary leucine. Statistical analysis of live weight gain, FCR, PER and BPD data re£ected signi¢cant di¡erences (Po0.05) among treatments. Live weight gain, FCR, PER and BPD data were also analysed using second-degree polynomial regression analysis to obtain more accurate leucine requirement estimate which was found to be at 1.57, 1.55, 1.52 and 1.50 g per 100 g of dry diet, corresponding to 3.92, 3.87, 3.80 and 3.75 g per 100 g of dietary protein respectively. Based on the quadratic regression analysis of the live weight gain, FCR, PER and BPD data, the optimum requirement of ¢ngerling L. rohita for leucine is estimated to be in the range of 1.50^1.57 g per 100 g of the dry diet, corresponding to 3.75^3.92 g per 100 g of dietary protein.

Indian major carp ¢ngerling, Cirrhinus mrigala (3.85 AE 0.75 cm, 0.52 AE 0.21g), were fed isonitrogenous and isocaloric diets (40% crude protein, 4.28 kcal g À 1 , gross energy) containing casein, gelatin and crystalline amino acids with graded levels of L-threonine (1.00, 1.25, 1.50, 1.75, 2.00 and 2.25 g100 g À 1 , dry diet) to determine the dietary threonine requirement. The feeding trial was conducted in triplicate for 8 weeks. Diets were fed twice a day at 08:00 and 16:00 hours at 5% body weight day À 1 . The ration size and feeding schedule were worked out before the start of the feeding trial.Highest weight gain (304%) and best feed conversion ratio (1.43) were evident in ¢sh fed diet containing 1.75% dietary threonine. Second-degree polynomial regression analysis of weight gain, feed conversion ratio and protein e⁄ciency ratio data indicated the dietary threonine requirement to be at 1.84%, 1.81% and 1.78%, respectively, corresponding to 4.60%, 4.52% and 4.45% of dietary protein. Minimum carcass moisture, fat and maximum carcass protein were evident in ¢sh fed 1.75% threonine level. However, ash content did not a¡ect body composition, except the 1.00% threonine level, which showed a signi¢cantly higher ash content value. Based on the above results, it is recommended that the diet for C. mrigala should contain threonine at 1.80 g100 g À 1 dry diet, corresponding to 4.50 g100 g À 1 dietary protein for optimum growth and e⁄cient feed utilization. Cirrhinus mrigala, dietary threonine requirement I Ahmed et al.Ã Mean value of three replicate AE SEM. Mean values with the same superscripts are insigni¢cantly di¡erent (P40.05).Aquaculture Research, 2004, 35, 162^170 Cirrhinus mrigala, dietary threonine requirement I Ahmed et al.

To quantify dietary L-tryptophan requirement of fingerling Heteropneustes fossilis (6.66 ± 0.08 g), casein-gelatin-based isonitrogenous (38% CP) and isoenergetic (14.72 kJ g À1 DE) purified diets with eight levels of L-tryptophan (0.12%, 0.16%, 0.20%, 0.24%, 0.28%, 0.32%, 0.36%, 0.40% dry diet) were fed to triplicate groups of fish twice daily to apparent satiation for 12 weeks. Incremental levels of dietary tryptophan from 0.12 to 0.28% significantly (P < 0.05) improved absolute weight gain (AWG; 14.3-65.9 g fish À1 ), feed conversion ratio (FCR; 5.9 -1.5), protein retention efficiency (PRE; 6.2-32.2%), haemoglobin (Hb; 6.5 to 11.9 g dL À1 ) and haematocrit (Hct; 23.5-33.8%).To determine the precise information on tryptophan requirement, data were subjected to broken-line and second-degree polynomial regression analysis. Broken-line regression analysis reflected highest R 2 values for AWG g fish À1 (0.999), PRE% (0.993), Hb g dL À1 (0.995) and Hct % (0.993) compared with R 2 values obtained using second-degree polynomial regression analysis of AWG g fish À1 (0.949), PRE% (0.890), Hb g dL À1 (0.969) and Hct% (0.943), indicating that data were better fit to broken-line regression analysis. Hence, based on broken-line regression analysis at 95% maximum response, tryptophan requirement of fingerling H. fossilis is recommended between 0.24% and 0.27% dry diet (0.63-0.71% protein).

An 8-week feeding trial was conducted in a flow-through system (1-1.5 L min -1 ) at 27°C to determine dietary protein requirement for Channa punctatus fingerlings (4.58 ± 0.29 g) by feeding six isocaloric diets (18.39 kJ g -1 , gross energy). Diets containing graded levels of protein (300, 350, 400, 450, 500 and 550 g kg -1 ) were fed to triplicate groups of fish to apparent satiation at 09:00 and 16:00 h. Maximum absolute weight gain (AWG; 8.11 g fish -1 ), specific growth rate (SGR; 1.82%) and best feed conversion ratio (FCR; 1.48) were recorded in fish fed diet containing 450 g kg -1 protein, whereas protein efficiency ratio (PER; 1.52), protein retention efficiency (PRE; 25%), energy retention efficiency (ERE; 78%) and RNA/DNA ratio (3.01) were maximum for the group fed dietary protein at 400 g kg -1 . Second-degree polynomial regression analysis of AWG, SGR and FCR data against varying levels of dietary protein yielded optimum dietary protein requirement of fingerling between 462.24 and 476.72 g kg -1 , whereas the regression analysis of PER, PRE, ERE and RNA/DNA ratio data showed a lower protein requirement of 438.28-444.43 g kg -1 of the diet. Considering the PER, PRE, ERE and RNA/DNA ratio as more reliable indicators, this protein requirement is recommended for developing quality protein commercial feeds for C. punctatus fingerlings.

Dietary arginine requirement of Heteropneustes fossilis fry (3.0 ± 0.5 cm; 5.1 ± 0.3 g) was determined by feeding casein‐gelatin‐based isonitrogenous (400 g kg−1 crude protein) and isocaloric (17.97 kJ g−1) amino acid test diets containing graded levels of l‐arginine (15, 17, 19, 21, 23 and 25 g kg−1 dry diet) for 12 weeks. Maximum absolute weight gain (AWG) (44.4), best feed conversion ratio (FCR) (1.22), highest protein retention efficiency (PRE%) (41%), energy retention efficiency (ERE%) (75%), best condition factor, hepatosomatic index and viscerosomatic index were noted at 21 g kg−1 arginine of the dry diet. Maximum body protein (189.8 g kg−1) was also obtained in fish fed above diet. Highest haematocrit value (35%), Hb concentration (9.54 g dL−1), RBC count (3.44 × 109 mL−1) and lowest Erythrocyte sedimentation rate (ESR) (1.93 mm h−1) were obtained at the above level of arginine in the diet. AWG, FCR, PRE% and ERE% data were analysed using broken‐line and an exponential fit to obtain more precise dietary arginine requirement. On the basis of broken‐line and exponential analyses of AWG, FCR, PRE and ERE data, inclusion of dietary arginine in the range of 20.4–22.6 g kg−1 dry diet, corresponding to 51–56.5 g kg−1 dietary protein, is recommended for formulating arginine‐balanced feeds for rearing H. fossilis fry.