A total of 180 Labeo rohita fry (1 g) were distributed into six treatment groups with three replicates each. Six isoenergetic (15.8 kJ g )1 ) diets were prepared with varying levels of protein (CP) and gelatinized carbohydrate (GC), viz. D 1 : 450 g kg )1 CP, 258 g kg )1 GC; D 2 : 400 g kg )1 CP, 302 g kg )1 GC; D 3 : 350 g kg )1 CP, 399 g kg )1 GC; D 4 : 301 g kg )1 CP, 447 g kg )1 GC; D 5 : 249 g kg )1 CP, 517 g kg )1 GC and control diet, D 6 : 400 g kg )1 CP, 468 g kg )1 GC and these were fed to fish at 40 g kg )1 wet body weight per day for 60 days. Highest growth was recorded for fish fed D 4 , decreasing for D 5 . Protein utilization, amylase activity and carbohydrate digestibility were significantly positively correlated with GC (P < 0.05) and were highest in fish fed D 5 . Hypertrophy of hepatic cells was only recorded for D 5 . Lysine, which may be affected during gelatinization, was estimated in diets and found to be above the minimum level required. Survival rate was unaffected by diet. The results of the present study indicate that a diet containing 450 g kg )1 GC and 300 g kg )1 CP was efficiently utilized by L. rohita fry. KEY WORDS

A feeding trial was conducted for 60 days to study the effects of exogenous microbial phytase supplementation on the growth and nutrient digestibility of Pangasius pangasius fingerlings. Eight isocaloric and isoprotein experimental diets (35.67% crude protein and 3870 kcal kg−1) were prepared with graded levels of phytase, e.g., 0 (T1), 150 (T2), 250 (T3), 350 (T4), 500 (T5), 1000 (T6) and 2000 (T7) FTU (phytase units)  kg−1. Three hundred and fifteen fingerlings of P. pangasius (1.97–2.05 g) were randomly distributed in seven treatments with three replicates each. Maximum weight gain (350.72%), specific growth rate (2.51%), protein efficiency ratio (2.1), apparent net protein utilization (27.85%), energy retention value (88.47%) and feed conversion efficiency were observed in T5 group supplemented with 500 FTU phytase kg−1 diet. Apparent dry matter and protein digestibility in phytase‐supplemented groups were significantly (P<0.01) higher at a minimum supplement of 500 FTU kg−1 or higher. Liver alkaline phosphatase activity increased significantly in treatment groups. Supplementation at 500 FTU kg−1 of phytase is optimum in the diet of P. pangasius fingerlings.

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A 2 × 2 × 2 factorial experiment was designed to study the effect of microbial phytase (MP), citric acid (CA), and crude protein (CP) and their interactions on mineral utilization by rohu, Labeo rohita, juveniles. Two basal diets containing 25% (subnormal) or 35% (normal) CP were supplemented with MP (units, U/kg) and CA (%) at 0, 0; 500, 0; 0, 3; and 500, 3, respectively and fed to 125 juveniles (average initial weight: 13.16 g/fish). MP did not affect fecal ash content but CA (3%) addition activated MP. Apparent absorption of Zn, its content in whole body and plasma, was significantly (P < 0.05) higher in CA‐ and MP‐fed groups. Interaction between CA and MP was found for increased absorption of Na, P, K, Mn, Mg, Fe, and N, their concentrations in whole body and plasma. Cu and Ca absorption, and their concentration in body and plasma were increased as a result of addition of CA, MP, or their interaction. Thus, bioavailability of major minerals was highest in groups fed diets containing 500‐U MP and 3% CA. This improvement was more prominent in subnormal CP diet. Growth performance was also highest in this group. Thus, CA and MP at 25% CP diet had synergistic effect on mineral bioavailability in L. rohita.

Jatroha protein concentrate (JPC) was prepared by iso-electric precipitation method. A 45-day feeding trial was conducted for the nutritional evaluation of JPC and fermented Jatropha protein concentrate (FJPC) in Labeo rohita fingerlings. Seven iso-nitrogenous (340 g kg À1 CP) and iso-energetic (17 MJ kg À1 ) diets such as C (soy protein concentrate ) , T 1 (50 g kg À1 JPC), T 2 (100 g kg À1 JPC), T 3 (200 g kg À1 JPC), T 4 (50 g kg À1 FJPC), T 5 (100 g kg À1 FJPC) and T 6 (200 g kg À1 FJPC) were fed to respective groups. The weight gain % and protein effciency ratio showed a decreasing trend with higher inclusion of JPC whereas these parameters increased gradually on higher inclusion of FJPC. FCR showed the reverse trend. The protease, GOTand GPT activities of FJPC fed groups were significantly higher than their non-fermented counterparts whereas a reverse trend was observed for LDH and MDH enzyme activities in muscle and liver. The survival rate was 100% in all the treatment groups except for T 2 and T 3 . Phorbol esters (PEs) in FJPC was non-detectable. Results suggested that solid state fermentation with Aspergillus niger is an effective method for removal of PEs and FJPC is a promising protein source in aquafeed.

Five iso-nitrogenous (300 g kg )1 diet) purified diets with graded level of lipid at 40 (D-1), 60 (D-2), 80 (D-3), 100 (D-4) and 120 (D-5) g kg )1 diet were fed to Puntius gonionotus fingerlings for 90 days to determine their dietary lipid requirement. Two hundred and twenty-five fingerlings (average weight 2.34 ± 0.03 g) were equally distributed in five treatments in triplicate groups with 15 fish per replicate. Fifteen flow-through cement tanks of 100 L capacity with a flow rate of 0.5 L min )1 were used for rearing the fish. Specific growth rate (SGR), feed conversion ratio (FCR), nutrient digestibility, retention, digestive enzyme activity, RNA : DNA ratio and whole-body composition were considered as the response parameters with respect to dietary lipid levels. Maximum SGR and minimum FCR with highest RNA : DNA ratio, whole-body protein content and digestive enzyme activity was found in D-3 group fed with 80 g kg )1 diet lipid. Nutrient digestibility was similar in all the groups irrespective of the dietary lipid level. Maximum protein and energy retention was recorded at 80 g kg )1 dietary lipid fed group. However, from the second-order polynomial regression analysis, the maximum growth of P. gonionotus fingerlings was found at 96.9 g lipid kg )1 diet. KEY WORDS

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A 60-days feeding trial was conducted to delineate the effect of both gelatinized and non-gelatinized corn with or without supplementation with exogenous a-amylase at two dietary protein levels (35% and 28%) on dry matter digestibility, digestive enzymes and tissue glycogen content of Labeo rohita juveniles. Three hundred and sixty juveniles (average weight 10±0.15 g] were randomly distributed into 12 treatment groups with each of two replicates. Twelve semi-purified diets containing either 35% or 28% crude protein were prepared by including gelatinized (G) or non-gelatinized (NG) corn as carbohydrate source with different level of microbial a-amylase (0, 50, 100 and 150 mg kg -1 ). The dry matter digestibility of G corn fed groups was significantly higher (P < 0.05) than that of the NG corn fed groups. Hepatosomatic index (HSI), liver glycogen and intestinal amylase activity of G starch fed groups were significantly higher (P < 0.05) than those of the NG corn fed groups. However, the reverse trend was found for gastrosomatic index (GSI), muscle glycogen and intestinal protease activity. Addition of 50 mg a-amylase kg -1 feed improved the dry matter digestibility of NG starch fed groups, which was similar to that of the G corn fed groups or NG corn supplemented with 100/150 mg a-amylase kg -1 feed. HSI, liver glycogen and intestinal amylase activity were significantly increased (P < 0.05) at minimum level of a-amylase in the feed (50 mg kg -1 ) and did not increase due to further inclusion of amylase in the diet. Supplementation with a-amylase at 50 mg kg -1 increased the intestinal amylase activity beyond which no significant changes were observed. Protease activity of liver and intestine was highest (P < 0.05) in higher crude protein (CP) fed groups, but protease activity of the intestine was significantly higher in the a-amylase supplemented groups. Hence, it was concluded that feed with 28% CP containing either G corn without a-amylase or NG corn with 50 mg a-amylase kg -1 may be used as the alternative carbohydrate source for L. rohita juveniles.