Quantitative dietary isoleucine requirement of juvenile Pacific white shrimp,Litopenaeus vannamei (Boone) reared in low-salinity water

This study was designed to determine the isoleucine requirement of juvenile Pacific white shrimp Litopenaeus vannamei (Boone) in low-salinity water (0.50–0.70 g L^?1). Six diets were formulated to contain 410 g kg^?1 crude protein with fish meal, peanut meal and pre-coated crystalline amino acids with different concentration of l-isoleucine (9.35, 11.85, 14.35, 16.85, 19.35, and 21.85 g kg^?1 dry diet, defined as diet I1, diet I2, diet I3, diet I4, diet I5 and diet I6, respectively.). Each diet was randomly assigned to triplicate treatments of 30 shrimps (0.43 ± 0.005 g), and the feed trial lasted for 8 weeks. The results indicated that the weight gain significantly increased with increasing isoleucine concentration up to 14.35 g kg^?1 (diet I3), whereas it was reduced in the treatments exceeding 16.85 g kg^?1 isoleucine (diet I4) significantly (P < 0.05). Moreover, the highest body protein deposition and protein efficiency ratio, and the lowest feed conversion ratio, haemolymph aspartate aminotransferase and alanine aminotransferase activities were also found at treatment I3–I4 (P < 0.05). And the haemolymph urea nitrogen concentration of shrimps-fed diet I6 was particularly higher than those fed with diets I1–I5 (P < 0.05). The results of polynomial regression based on weight gain, feed efficiency and body protein deposition indicated that the optimal dietary isoleucine requirement for L. vannamei reared in low-salinity water was 15.95 g kg^?1 isoleucine of dry diet, correspondingly 38.81 g kg^?1 of dietary protein.     

Dietary histidine requirement of fingerling Catla Catla (Hamilton) based on growth,protein gain,histidine gain,RNA/DNA ratio,haematological indices and carcass composition

To investigate the histidine requirement of fingerling Catla catla (3.65 ± 0.15 cm; 0.65 ± 0.36 g), six casein‐gelatin based diets (33% CP; 13.58 kJ g^?1 DE) containing graded levels of L‐histidine (0.25%, 0.39%, 0.53%, 0.67%, 0.83%, 0.96% of the dry diet) were fed near to satiation thrice a day for 12 weeks. Maximum absolute weight gain (AWG; 8.63 g fish^?1), protein gain (PG; 1.45 g fish^?1), histidine gain (HG, 48.19 mg fish^?1), RNA/DNA ratio (4.15), best feed conversion ratio (FCR; 1.31), highest haemoglobin (Hb, 9.61 g dL^?1), RBCs (2.84 × 10⁶ mm^?3) and haematocrit (Ht, 30.12%) were recorded in fish fed diet containing 0.67% histidine. However, broken‐line regression analysis of AWG, PG, HG, RNA/DNA ratio, FCR, Hb, Ht and RBCs against dietary histidine reflected the histidine requirement at 0.65%, 0.64%, 0.63%, 0.68%, 0.63%, 0.66%, 0.68% and 0.65% dry diet respectively. Carcass protein was found to improve significantly (P < 0.05) from 13.36% to 16.42% with the increase in dietary histidine from 0.25% to 0.67%. Based on regression analysis of AWG, PG, HG, RNA/DNA ratio, FCR, Hb, Ht and RBCs, it is recommended that the diet for fingerling catla should contain histidine in the range of 0.63–0.68% dry diet, equivalent to 1.91–2.06% of the dietary protein for optimum growth, feed utilization, blood profile and carcass composition.     

Dietary threonine requirement of fingerling Indian major carp,Labeo rohita (Hamilton)

An 8‐week feeding experiment was conducted in a water flow‐through system (26–28 °C) to determine the dietary threonine requirement of fingerling Labeo rohita (3.90±0.03 cm; 0.58±0.02 g). Growth, feed utilization and body composition of fish fed test diets (40% crude protein; 17.9 kJ g^?1 gross energy) with graded levels of l ‐threonine (0.75%, 1.0%, 1.25%, 1.50%, 1.75% and 2.0% dry diet) to apparent satiation were response variables used to assess threonine adequacy. Diets were made isonitrogenous and isoenergetic by adjusting the levels of glycine and dextrin. The amino acid profiles of the test diets were formulated to that of 40% whole chicken egg protein except for threonine. The performance of fish fed experimental diets was evaluated using calculated values for weight gain (g fish^?1), feed conversion ratio (FCR), protein efficiency ratio (PER) and protein productive value (PPV) data. Maximum weight gain (g fish^?1) (1.79), lowest FCR (1.39), highest PER (1.76) and PPV (0.33) were recorded at 1.50 g per 100 g dietary threonine. Statistical analysis of weight gain, FCR, PER and PPV data reflected significant differences (P<0.05) among treatments. Except for reduced growth performance in fish fed threonine‐deficient diets, no deficiency signs were noted. Weight gain, FCR, PER and PPV data were also analysed using second‐degree polynomial regression analysis to obtain a more accurate threonine requirement estimate, which was found, using each response variable, to be at 1.70, 1.63, 1.65 and 1.51 g per 100 g of dry diet, corresponding to 4.2, 4.07, 4.12 and 3.77 g per 100 g of dietary protein respectively. Based on the second‐degree polynomial regression analysis of the live weight gain, FCR, PER and PPV data, the optimum dietary level of threonine for fingerling L. rohita was found to be in the range of 1.51–1.70 g per 100 g of the dry diet, corresponding to 3.77–4.2 g per 100 g of dietary protein.     

Dietary arginine requirement of fingerling Indian catfish (Heteropneustes fossilis, Bloch)

An 8-week feeding trial was conducted to determine the dietary arginine requirement of fingerling Indian catfish, Heteropneustes fossilis (6.25 ± 1.30 cm, 4.8 ± 0.65 g). Six isonitrogenous (400 g Kg^?1) and isoenergetic (17.90 kJ g^?1) amino acid test diets were formulated with gradation of 2.5 g Kg^?1 containing graded levels of l-arginine (8.5–21.0 g Kg^?1, dry diet). Fish were randomly stocked in triplicate groups, in 75-l circular trough with flow-through system and fed experimental diets at 4 % BW/day at 0800 and 1800 h. Maximum live weight gain (277 %), best feed conversion ratio (FCR) (1.52) and protein efficiency ratio (PER) (1.64) were obtained in fish fed diet containing 16.0 g Kg^?1 arginine. However, quadratic regression analysis of live weight gain, FCR, PER and body protein deposition (BPD) data indicated requirements for dietary arginine at 16.80, 16.30, 16.11 and 16.10 g Kg^?1 of dry diet, respectively. Significantly (p < 0.05) higher whole body protein content, minimum carcass moisture and intermediate carcass fat contents were recorded at 16.0 g Kg^?1 dietary arginine diet. Ash content remained insignificantly (p > 0.05) low among all the treatments except at diet I and diet II. Based on the above results, it is recommended that the diet for young H. fossilis should contain arginine at 16.32 g Kg^?1, dry diet, corresponding to 40.80 g Kg^?1 dietary protein for optimum growth and efficient feed utilization.     

Dietary amino acid l-tryptophan requirement of fingerling Indian catfish, Heteropneustes fossilis (Bloch), estimated by growth and haemato-biochemical parameters

An 8-week feeding trial was conducted to determine the dietary tryptophan requirement of fingerling Indian catfish, Heteropneustes fossilis (6.10 ± 1.15 cm, 4.44 ± 0.50 g). Six isonitrogenous (40 g 100 g^?1) and isoenergetic (17.90 kJ g^?1) amino acid test diets were formulated with gradation of 0.1 g 100 g^?1 containing graded levels of l-tryptophan (0.04–0.54 g 100 g^?1, dry diet). Fish were stocked in triplicate groups, in 75-L circular trough with flow-through system and fed experimental diets at 4% BW/day twice daily. Maximum live weight gain (258%), best feed conversion ratio (FCR) (1.54) and protein efficiency ratio (PER) (1.62) were obtained in fish fed diet containing 0.34 g 100 g^?1 tryptophan. However, quadratic regression analysis of weight gain, FCR, PER and body protein deposition (BPD) data indicated requirements for dietary tryptophan at 0.37, 0.33, 0.32 and 0.33 g 100 g^?1 of dry diet, respectively. Significantly (P < 0.05) higher body protein, minimum moisture and intermediate fat contents were recorded at 0.34 g 100 g^?1 dietary tryptophan diet. Ash content was not significantly different (P > 0.05) among treatments except for diets 0.04 and 0.14 g 100 g^?1. Excellent somatic and haematological indices values were obtained at the requirement level. Based on above results, it is recommended that the diet for H. fossilis should contain tryptophan at 0.32 g 100 g^?1, dry diet, corresponding to 0.80 g 100 g^?1 dietary protein for optimum growth and efficient feed utilization.     

Dietary threonine requirement of fingerling Indian major carp,Catla catla (Hamilton) estimated by growth,protein retention efficiency,threonine deposition,haematological parameters and carcass composition

A 12‐week feeding trial was conducted to determine the dietary threonine requirement of fingerling Indian major carp, Catla catla (3.35 ± 0.11 cm; 0.59 ± 0.06 g). Six casein‐gelatin based (33% crude protein; 3.23 kcal g^?1 digestible energy) amino acid test diets with graded levels of analysed threonine (0.74%, 0.96%, 1.21%, 1.48%, 1.72% and 1.93% dry diet) were fed to satiation to triplicate groups of fish. Absolute weight gain (g per fish), feed conversion ratio, protein retention efficiency, threonine deposition, RNA/DNA ratio and carcass protein significantly improved with the increase in dietary threonine and peaked at 1.48% of the dry diet. Haematological indices were also found to be best in fish fed at 1.48% threonine diet. Quadratic regression analysis of absolute weight gain, feed conversion ratio, protein retention efficiency, threonine deposition, RNA/DNA ratio, carcass protein, haemoglobin (g dL^?1), haematocrit (%) and RBCs (10⁶ × mm^?3) at 95% of maximum and minimum response exhibited the threonine requirement of fingerling C. catla between 1.35% and 1.48% dry diet, corresponding to 4.09–4.48% dietary protein. Present finding would be useful in formulating threonine‐balanced feeds for the intensive culture of C. catla.     

Dietary isoleucine requirement of juvenile blunt snout bream,Megalobrama amblycephala

A 9‐week feeding trial was conducted to estimate the dietary isoleucine requirement of juvenile blunt snout bream. Six isonitrogenous and isoenergetic experimental diets were formulated to contain graded isoleucine levels ranging from 5.3 to 20.1 g kg^?1 dry diet. At the end of the experiment, weight gain (WG), specific growth rate (SGR), feed efficiency ratio (FER) and protein efficiency ratio (PER) increased with increasing dietary isoleucine level up to 11.1 g kg^?1 dry diet, and dietary isoleucine level above 14.2 g kg^?1 dry diet declined these performances. Dietary isoleucine levels (14.2 and 17.3 g kg^?1 dry diet) significantly improved whole‐body protein content, but decreased whole‐body lipid, plasma triglyceride and cholesterol contents. Significantly lower visceral fat index (VFI) in fish fed with 14.2 g kg^?1 dietary isoleucine was observed compared to those fed with deficient or excessive isoleucine. Dietary isoleucine supplementation significantly increased plasma isoleucine concentration, while plasma valine and leucine concentrations showed a reversed trend. Dietary isoleucine levels regulated the target of rapamycin (TOR) gene expression and improved plasma superoxide dismutase (SOD) activity in juvenile blunt snout bream. Based on second‐order polynomial regression model analysis of SGR and FER, the optimum dietary isoleucine requirement was estimated to be 13.8 g kg^?1 dry diet (40.6 g kg^?1 dietary protein) and 14.0 g kg^?1 dry diet (41.2 g kg^?1 dietary protein), respectively.     

Dietary Arginine Requirement of Fingerling Indian Major Carp,Catla catla (Hamilton)

Dietary arginine requirement of fingerling Catla catla (3.55 ± 0.05 cm; 0.61 ± 0.02 g) was determined by feeding casein–gelatin‐based isonitrogenous (33% crude protein) and isocaloric (3.40 kcal/g digestible energy) amino acid test diets containing six graded levels of l ‐arginine (1, 1.25, 1.5, 1.75, 2, and 2.25% dry diet) for 12 wk. Maximum absolute weight gain (6.93 g/fish), protein efficiency ratio (2.13), protein deposition (0.36), arginine retention efficiency (78%), and best feed conversion ratio (1.42) were recorded in fish fed 1.75% arginine of the dry diet. Maximum carcass protein (15.57%) and RNA/DNA ratio (4.79) were also recorded for the group fed 1.75% arginine of the dry diet. Quadratic regression analysis at 95% maximum or minimum response of above growth parameters yielded optimum arginine requirement of fingerling C. catla at 1.67% of the dry diet. On the basis of the above analysis of the growth parameters, it is recommended that the inclusion of dietary arginine at 1.67% of the dry diet is optimum for formulating arginine‐balanced, cost‐effective quality feeds for the mass culture of fingerling C. catla .     

Dietary lysine requirement of fingerling Catla catla (Hamilton) based on growth, protein deposition, lysine retention efficiency, RNA/DNA ratio and carcass composition

A 12-week experiment was conducted to quantify dietary lysine requirement of fingerling Catla catla (3.65 ± 0.05 cm; 0.58 ± 0.02 g) by feeding casein–gelatine-based diets (33.0 % crude protein; 14.3 kJ/g digestible energy) with six levels of l-lysine (1.25, 1.50, 1.75, 2.00, 2.25 and 2.50 % dry diet). The experiment was conducted in eighteen 70-L indoor polyvinyl circular troughs provided with a water flow-through system (1–1.5 L/min). Live weight gain (LWG), feed conversion ratio (FCR), protein deposition (PD), lysine retention efficiency (LRE%) and RNA/DNA ratio were used as the response criteria. Second-degree polynomial regression analysis at 95 % maximum and minimum response of LWG and FCR data exhibited the lysine requirement between 1.8 and 1.9 % dry diet, corresponding to 5.5–5.7 % dietary protein. Regression analysis of PD, LRE and RNA/DNA ratio yielded the requirement between 1.7 and 1.8 % dry diet, corresponding to 5.2–5.5 % dietary protein. Since live weight gain and protein deposition are the key parameters for estimating nutrient requirement, these tools were used to recommend the lysine requirement of fingerling C. catla which ranges between 1.7 and 1.8 % dry diet. Data generated during this study will be useful to formulate lysine-balanced feed for intensive culture of this fish.     

Dietary l‐lysine requirement of fingerling stinging catfish,Heteropneustes fossilis (Bloch) for optimizing growth,feed conversion,protein and lysine deposition

Dietary lysine requirement of fingerling Heteropneustes fossilis (6.96 ± 0.05 g) was quantified by conducting 12‐week feeding trial in a flow‐through system at 28°C. Casein–gelatin based isonitrogenous (38% CP) and isocaloric (14.7 kJ g^?1 DE) amino acid test diets with six levels of dietary lysine (1.5%, 1.75%, 2.0%, 2.25%, 2.5%, 3.0% dry diet) were fed to apparent satiation in triplicates. Broken‐line and second‐degree polynomial regression analyses at 95% plateau of absolute weight gain (AWG; g fish^?1), feed conversion ratio (FCR), protein deposition (PD; g fish^?1) and lysine deposition (LD; g fish^?1) exhibited lysine requirement between 2.0% to 2.3% of the dry diet, corresponding to 5.3–6.1% protein.     

Dietary isoleucine requirement of fingerling Indian major carp, Labeo rohita (Hamilton)

An 8‐week feeding experiment was conducted to quantify the dietary isoleucine requirement of fingerling Indian major carp, Labeo rohita (3.50 ± 0.04 cm; 0.40 ± 0.02 g) using amino acid test diets (400 g kg⁻¹ crude protein; 17.90 kJ g⁻¹ gross energy) containing casein, gelatin and l ‐crystalline amino acids. Six dietary treatments supplemented with graded levels of isoleucine (7.5, 10.0, 12.5, 15.0, 17.5 and 20.0 g kg⁻¹), in gradations of 2.5 g kg⁻¹ diet, were fed to triplicate groups of fingerlings to apparent satiation divided over two feedings at 07:00 and 17:30 h. Performance of the fish was evaluated on the basis of live weight gain, feed conversion ratio (FCR), protein efficiency ratio (PER), specific growth rate (SGR) and protein productive value (PPV). Statistical analysis of live weight gain, FCR, PER, SGR and PPV reflected significant differences among treatments. Live weight gain and conversion efficiencies were best with isoleucine at 15.0 g kg⁻¹ of diet. Live weight gain, FCR, PER, SGR and PPV data were also analysed using second‐degree polynomial regression analysis to obtain more accurate isoleucine requirement estimate which was found to be at 15.9, 15.3, 15.2, 15.8 and 15.7 g kg⁻¹ of dry diet, corresponding to 39.8, 38.3, 38.0, 39.5 and 39.3 g kg⁻¹ of dietary protein respectively. Based on the quadratic regression analysis of the live weight gain, FCR, PER, SGR and PPV, the optimum level of isoleucine for fingerling L. rohita is in the range of 15.2–15.9 g kg⁻¹ of dry diet, corresponding to 38.0–39.8 g kg⁻¹ of dietary protein. Maximum body protein, minimum moisture and fat were noted at 15.0 g kg⁻¹ of dietary isoleucine while the body ash remained constant among all the treatment levels. No mortality was recorded during the duration of the experiment.     

Growth,feed conversion and body composition of fingerling stinging catfish Heteropneustes fossilis (Bloch) fed varying levels of dietary l‐threonine

An 8‐week feeding trial was conducted to assess the effects of dietary l ‐threonine on growth, protein utilization, threonine retention efficiencies, nucleic acid indices and body composition of fingerling Heteropneustes fossilis (6.6 ± 0.1 g; 10.9 ± 0.2 cm). Casein–gelatin based isonitrogenous (38% crude protein; CP) and isocaloric (15.3 kJ g^?1 digestible energy; DE) amino acid test diets with six levels of dietary l ‐threonine (0.75%; 1.0%; 1.25%; 1.5%; 1.75%; 2.0% dry diet) were prepared and hand‐fed to quadruplicate groups of fingerling to apparent visual satiation twice daily. Weight gain (WG; 46.3 g fish^?1), feed conversion ratio (FCR; 1.98), protein utilization efficiency (PUE; 0.25), threonine retention efficiency (TRE; 0.69), lipid productive value (LPV; 0.45), body protein (18.2%) and RNA/DNA ratio (3.6) of fish fed graded levels of dietary threonine increased significantly (P < 0.05) up to 1.49% threonine of dry diet. To generate precise information, the WG, RNA/DNA and LPV data were subjected to broken‐line and quadratic regression analyses. The two models were superimposed and requirement was determined by establishing the point, where the quadratic curve first intersected the plateau of broken‐line. Based on the above mathematical analyses, optimum dietary threonine requirement of fingerling H. fossilis was estimated to range between 1.62% and 1.69% of the diet, corresponding to 4.26–4.44% protein.     

Effects of practical dietary protein to lipid levels on growth,digestive enzyme activities and body composition of juvenile rice field eel (Monopterus albus)

A 10-week feeding experiment was conducted to evaluate the effects of dietary protein to lipid ratios (P/L) on growth, intestinal digestive enzyme activities and body composition in juvenile rice field eel (Monopterus albus) (initial mean body weight of 65.76 ± 1.07 g, mean ± SEM). Nine test diets were formulated in a 3 × 3 factorial design to contain three protein levels (350, 400 and 450 g kg^?1) for each of three lipid levels (40, 80 and 120 g kg^?1), respectively. Each diet was randomly assigned to triplicate groups of 60 fish per net cage (1.5 × 2.0 × 1.5 m). Results showed the survival was above 96 % and was not affected by dietary treatments. Fish fed the diet with 450 g kg^?1 protein and 40 g kg^?1 lipid showed the best weight gain (WG) (103.95 %) and feed conversion ratio (1.60) (P < 0.05). WG, protein efficiency ratio and energy retention increased with the increasing in lipid at 350 g kg^?1 protein level (P < 0.05). However, WG showed a little decline with increasing dietary lipid when fish fed the diets with 400 and 450 g kg^?1 protein level, but no significant difference was observed (P < 0.05). Hepatosomatic index, visceralsomatic index and intestinal lipase activity increased with the increasing of dietary lipid level irrespective protein level. Intestinal trypsin activity increased with the increasing of dietary lipid level when fish fed the diets with 350 g kg^?1 protein, but showed converse trend when fish fed the diets with 400 and 450 g kg^?1 protein. Serum triglyceride, body lipid and energy were positively correlated with the dietary lipid. Results of the present study showed that the dietary protein/lipid ratio of 450/40 g kg^?1 is considered optimum for rice field eel under culture conditions, and the increase in dietary lipid level has no efficient protein-sparing effect when fish fed the diets with 400 and 450 g kg^?1 protein level.     

Dietary tryptophan requirement of fingerling Catla catla (Hamilton) based on growth,protein gain,RNA/DNA ratio,haematological parameters and carcass composition

A 12‐week feeding trial was conducted in eighteen 70 L indoor polyvinyl circular troughs provided with a water flow‐through system (1–1.5 L min^?1) at 28 ± 1 °C to evaluate the dietary tryptophan requirement of fingerling Catla catla (3.45 ± 0.24 cm; 0.60 ± 0.13 g). Six casein‐gelatin‐based amino acid test diets (330 g kg^?1 crude protein; 13.6 kJ g^?1 digestible energy) containing graded levels of L‐tryptophan (1.0, 1.4, 1.9, 2.3, 2.8, 3.4 g kg^?1 dry diet) were fed to triplicate groups of fish near to satiation at 08:00, 12:30 and 17:30 h. Absolute weight gain, feed conversion ratio, protein gain, RNA/DNA ratio, hepatosomatic index, viscerosomatic index, condition factor and haematological indices improved with the increasing levels of tryptophan from 1.0 to 2.3 g kg^?1 of dry diet. Significantly higher carcass protein was obtained at 2.3 g tryptophan per kilogram of the dry diet. Exponential analysis of absolute weight gain, feed conversion ratio, protein gain and RNA/DNA ratio against dietary tryptophan levels at 95% maximum and minimum responses displayed the tryptophan requirement at 2.5, 2.3, 2.5 and 2.1 g kg^?1 dry diet, respectively. Inclusion of dietary tryptophan in the range of 2.1–2.5 g kg^?1 dry diet, equivalent to 6.4–7.6 g kg^?1 dietary protein, is recommended in formulating tryptophan‐balanced feed for the culture of this fish species.     

Dietary arginine requirement of fingerling Indian major carp, Cirrhinus mrigala (Hamilton)

Dietary arginine requirement of fingerling Indian major carp, Cirrhinus mrigala (4.20 ± 0.05 cm; 0.60 ± 0.02 g) was determined by conducting a 8‐week feeding trial with casein–gelatine‐based diets (400 g kg^?1 crude protein; 17.90 kJ g^?1, gross energy), containing crystalline amino acids with graded levels of l ‐arginine (10, 12.5, 15, 17.5, 20 and 22.5 g kg^?1, dry diet). Fish were randomly stocked, in triplicate groups, in 55‐L indoor polyvinyl flow through circular tanks and fed experimental diets at 5% of their body weight divided into two feedings at 08.00 and 16.00 hours. Live weight gain (321%) and feed conversion ratio (FCR 1.40) were significantly (P < 0.05) higher in fish fed diet containing 17.5 g kg^?1dietary arginine compared with other diets. Second‐degree polynomial regression analysis of live weight gain, FCR and protein efficiency ratio data indicated requirements for dietary arginine at 18.7, 18.4 and 18.3 g kg^?1 of the dry diet, respectively. Maximum carcass protein, and minimum moisture and fat contents were noticed at the requirement level. Carcass ash content remained insignificantly different among the treatments except at 17.5 g kg^?1 dietary arginine showing significantly higher ash content. Based on the above results, it is recommended that the diet for fingerling C. mrigala should contain arginine at 18.4 g kg^?1, dry diet, corresponding to 46 g kg^?1 dietary protein for optimum growth and efficient feed utilization.     

Effects of dietary arginine levels on growth, feed conversion, protein productive value and carcass composition of stinging catfish fingerling Heteropneustes fossilis (Bloch)

A 12-week feeding trial was conducted to evaluate the effects of varying levels of dietary arginine on growth, feed conversion, protein productive value and carcass composition of fingerling Heteropneustes fossilis (10.11?±?0.14?cm; 5.87?±?0.07?g). Casein and gelatin-based isonitrogenous (38% crude protein) and isocaloric (14.72 kJ?g^?1 digestible energy) amino acid test diets with varying levels of l-arginine (1.00, 1.25, 1.50, 1.75, 2.00 and 2.25?g 100?g^?1 of dry diet) were fed to randomly assigned triplicate groups of fish to apparent satiation twice daily at two feeding schedules (08.00 and 17.30?h). Thermal growth coefficient (TGC; 0.86), feed conversion ratio (FCR; 1.97) and protein productive value (PPV; 0.25) were best attained by the group fed diet containing 1.75?g arginine 100?g^?1 of dry diet (D4). Carcass protein content also peaked at the above level of dietary arginine whereas carcass lipid showed consistent drop with the increase in dietary arginine level up to 1.75?g 100?g^?1 of dry diet. Second-degree polynomial regression analysis at 95% maximum and minimum response of thermal growth coefficient, feed conversion, protein productive value, carcass protein and lipid productive value against varying levels of dietary arginine yielded that dietary arginine in the range of 1.51–1.66?g 100?g^?1 of dry diet, corresponding to 3.97–4.37?g 100?g^?1 protein is adequate to optimize growth, feed conversion, protein productive value and improve carcass quality in fingerling H. fossilis.     

Dietary L‐tryptophan requirement of fingerling stinging catfish,Heteropneustes fossilis (Bloch)

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^?1 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^?1), 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^?1) 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 R² values for AWG g fish^?1 (0.999), PRE% (0.993), Hb g dL^?1 (0.995) and Hct% (0.993) compared with R² values obtained using second‐degree polynomial regression analysis of AWG g fish^?1(0.949), PRE% (0.890), Hb g dL^?1(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).     

Evaluation of feeding rate based on growth,feed conversion,protein gain and carcass quality of fingerling Indian major carp,Catla catla (Hamilton)

The effects of feeding rates on growth, feed conversion, protein deposition and carcass quality of fingerling Catla catla (3.61 ± 0.03 cm; 0.71 ± 0.04 g) were worked out by conducting a 16‐week feeding trial. Fingerlings were fed with a casein‐gelatin‐based purified diet (40% crude protein CP; 14.95 MJ kg^?1 digestible energy; DE) at 1%, 2%, 3%, 4%, 5%, 6% and 7% body weight per day. The absolute weight gain (AWG; 10.50 g fish^?1) and feed conversion ratio (FCR; 1.41) were highest at the feeding rate of 5% body weight per day. However, protein gain (PG; 0.36 g fish^?1) and carcass protein content attained the maximum values at 4% BW day^?1. Quadratic regression analyses of AWG g fish^?1 and PG g fish^?1 at 95% maximum response indicated that these parameters attained the best values at 4.19% and 3.81% BW day^?1. On the basis of the above results it is recommended that the feeding rate in the range of 3.81–4.19% BW day^?1 with a P:E ratio of 26.69–27.74 mg protein MJ^?1 DE is optimum for maximum growth, efficient feed conversion and best carcass quality in fingerling C. catla.     

Dietary copper requirement of fingerling Channa punctatus (Bloch) based on growth,feed conversion,blood parameters and whole body copper concentration

A 12‐week feeding trial was conducted to estimate the dietary copper requirement of fingerling Channa punctatus. Six casein?gelatin‐based test diets (450 g kg^?1 crude protein; 18.81 kJ g^?1 gross energy) with graded levels of copper as copper sulphate (3.7, 4.7, 5.7, 6.7, 7.7 and 8.7 mg copper equivalent kg^?1 diet) were formulated and fed to triplicate groups of fish (7.25 ± 0.81 cm; 5.21 ± 0.27 g) near to satiation. Fish fed diet with 6.7 mg kg^?1 copper had highest absolute weight gain (AWG; 51.63 g fish^?1), protein efficiency ratio (PER; 1.42 g fish^?1), protein gain (PG; 8.34 g fish^?1), haemoglobin (Hb; 9.68 g dL^?1), haematocrit (Hct; 31.18%) and RBCs (3.24 × 10⁶ × mm^?3). Feed conversion ratio (FCR) was found to be best (1.57) at above level of dietary copper. Whole body copper concentration was found to increase with the increasing levels of dietary copper. Hepatic thiobarbituric acid‐reactive substances concentration was found to decrease with increasing dietary concentrations of copper up to 6.7 mg kg^?1 beyond which a reverse trend in this parameter was noted. Broken‐line regression analysis of AWG, FCR and PG concentrations against varying levels of dietary copper yielded the requirement in the range of 6.66–6.78 mg kg^?1. Data generated during this study would be useful in formulating copper‐balanced commercial feeds for the intensive culture of this fish.     

Dietary tryptophan requirement of fingerling Indian major carp, Cirrhinus mrigala (Hamilton)

An 8‐week feeding trial was conducted to evaluate the effects of dietary tryptophan concentration on weight gain and feed efficiencies of fingerling Indian major carp, Cirrhinus mrigala. Six isonitrogenous (40% crude protein) and isocaloric (17.90 kJ g^?1) amino acid test diets containing casein, gelatin and l ‐crystalline amino acids with graded levels of l ‐tryptophan (0.06, 0.16, 0.26, 0.36, 0.46 and 0.56 g 100 g^?1 dry diet) were formulated. Fish (4.25±0.30 cm, 0.62±0.02 g) were randomly stocked in triplicate groups in 70 L (water volume 55 L) flow‐through (1–1.5 L min^?1) indoor circular tanks and fed experimental diets at 5% of their body weight/day in two feedings at 08:00 and 16:00 hours. Maximum live weight gain (277%), lowest feed conversion ratio (FCR) (1.50) and highest protein efficiency ratio (PER) (1.66) were measured at 0.36% dietary tryptophan. The relationship between dietary tryptophan levels and weight gain, FCR and PER data were described using second‐degree polynomial regression analysis indicating the tryptophan requirement at 0.42, 0.39 and 0.38 g 100 g^?1 of dry diet respectively. Whole body moisture decreased with increasing tryptophan up to 0.36%. Significantly (P<0.05) higher protein content was evident in fish fed diet containing 0.36% tryptophan. Body fat increased significantly (P<0.05) in fish fed with different tryptophan concentrations except those fed 0.36% tryptophan where a significantly lower fat content was noted. Significantly (P<0.05) higher ash content was reported at 0.06% and 0.16% tryptophan levels. Survival was 100% in fish fed all the diets except those fed 0.06% tryptophan. Based on the results, diets for fingerling C. mrigala should contain tryptophan at 0.38 g 100 g^?1 dry diet, corresponding to 0.95 g 100 g^?1 dietary protein for optimum growth and efficient feed utilization.