Water soaking and exogenous enzyme treatment of plant-based diets: effect on growth performance, whole-body composition, and digestive enzyme activities of rohu, Labeo rohita (Hamilton), fingerlings

A 2 × 2 × 2 factorial experiment was conducted to delineate the main effect of water soaking of plant ingredients, phytase, cellulase, and their interactions on the growth and digestive enzyme activities of Labeo rohita fingerlings. Two basal diets were prepared using water-soaked (S) or unsoaked (US) plant-based ingredients. Feed of US ingredients was supplemented with phytase (U kg⁻¹) and cellulase (%) at the level of 0, 0 (C_us); 500, 0 (T₁); 0, 0.2 (T₂); 500, 0.2 (T₃), and feed of S ingredients at 0, 0 (C_s); 500, 0 (T₄); 0, 0.2 (T₅), and 500, 0.2 (T₆), respectively. Three hundred and sixty fingerlings were randomly distributed into eight treatments, each with three replicates. Soaking of the ingredients for 24 h significantly reduced the tannin content. However, feeding of S diets did not improve the fish growth. Highest performance was recorded in the T₃ group. A significant interaction between dietary phytase and cellulase was observed for apparent net protein utilization. Tissue crude protein, ether extract, and ash content of the fingerlings were observed highest in the T₃ group. Activities of amylase, protease, and lipase were recorded highest in the T₃ group. Results suggested that soaking of plant-based ingredients reduces tannin content; however, growth and digestive enzyme activities of group fed soaked diet were not improved, possibly due to leaching of soluble nutrients. Probably, a shorter duration soaking may be effective in reducing tannin content and avoiding nutrients leaching.     

In vitro selection of a synbiotic and in vivo evaluation on intestinal microbiota,performance and physiological response of rainbow trout (Oncorhynchus mykiss) fingerlings

The aim of this study was to determine the best synbiotic combination (based on growth and short chain fatty acids production) between Pediococcus acidilactici and five prebiotics in vitro, inulin, fructooligosaccharide (FOS), xylooligosaccharide (XOS), galactooligosaccharide (GOS), isomaltooligosaccharide (IMO). The best in vitro growth under aerobic and anaerobic culture condition was observed in the treatment, P. acidilactici + GOS. Furthermore, the study of short chain fatty acids (SCFA) production at the end of exponential growth phase revealed that the major SCFA produced was propionic acid in all synbiotic treatments except for the P. acidilactici + GOS treatment where butyric acid production was significantly higher compared with the other treatments. Based on the results of in vitro studies, P. acidilactici + GOS that were selected as synbiotic and rainbow trout fingerlings (15.04 ± 0.52 g) were fed on diet supplemented with the selected synbiotic. After 8 weeks of feeding, growth performance, intestinal microbiota and physiological responses were evaluated. Growth performance was significantly improved by synbiotic feeding. No significant differences of haematological parameters were revealed between the different treatments. Level of presumptive autochthonous lactic acid bacteria was elevated, while total autochthonous bacterial level remained unaffected. These results showed that P. acidilactici + GOS can be considered as an efficient synbiotic for rainbow trout.     

Evaluating the Effects of Dietary Prebiotic Mixture of Mannan Oligosaccharide and Poly‐β‐Hydroxybutyrate on the Growth Performance,Immunity, and Survival of Rainbow Trout,Oncorhynchus mykiss (Walbaum 1792), Fingerlings

This study investigated the effects of dietary poly‐β‐hydroxybutyrate (PHB) and mannan oligosaccharide (MOS) on the growth performance, digestive enzyme activities, and disease resistance of rainbow trout fingerlings. A total of 420 fingerlings, distributed equally into four different groups, each with three replicates, were fed a basal diet (control), 2% PHB (PHB), 0.2% MOS (MOS), or a diet supplemented with a mixture of 2% PHB and 0.2% MOS (PHB+MOS) for 60 d. Results showed that dietary PHB and/or MOS did not cause significant improvement in the growth performance of the fingerlings. The gut pH was markedly reduced; however, the activities of the digestive enzymes (except for pepsin and amylase by dietary PHB) were not significantly improved by the dietary supplements. Results also showed that dietary PHB and/or MOS markedly increased the resistance of the fingerlings toward Yersinia ruckeri infection, while the lowest total antibody was observed in fish fed control and MOS, indicating that MOS exerts its protective effects by modulating other mechanisms. Overall, this study provided a first screening effort to determine the effects of PHB and/or MOS as dietary supplements in rainbow trout fingerlings to develop an optimal prebiotic mix for improving the growth and health status of rainbow trout.     

Effects of polysaccharide from fermented wheat bran on growth performance,muscle composition,digestive enzyme activities and intestinal microbiota in juvenile common carp

The present study evaluated the effect of dietary polysaccharide from fermented wheat bran on growth performance, muscle composition, digestive enzyme activities and intestinal microbiota of juvenile common carp (Cyprinus carpio L.). Four diets supplemented with 0 (D0), 1.0 (D1), 2.0 (D2) and 4.0 (D3) g/kg fermented wheat bran polysaccharide (FWBP) were prepared. Fish were randomly assigned into four groups, each group having four replicates (30 fish/replicate) and fed with experimental diets for 8 weeks. Compared with the D0 group, the D3 group had higher final body weight and weight gain (p < .05). The amylase activity in the intestine and hepatopancreas of D1 and D2 groups and pepsin and trypsin activities in the hepatopancreas of D2 and D3 groups were significantly higher than D0 group. Significantly increased muscle protein and lipid content while reduced moisture content was observed in D1 group; additionally, D3 group had significantly lower muscle lipid content. The population of Bifidobacterium spp. in the intestine digesta of D1 and D2 groups was significantly increased, whereas lactic acid bacteria (LAB) and Escherichia coli were unaffected. Collectively, dietary FWBP supplementation could enhance digestive enzyme activities and Bifidobacterium population and change the muscle composition and improve growth performance of common carp.     

Haemato-biochemical responses and induction of HSP70 to dietary phosphorus in <Emphasis Type="Italic">Catla catla</Emphasis> (Hamilton) fingerlings

A feeding trial of 120 days was conducted to study the effect of graded levels of dietary phosphorus on haematology, serum protein concentrations and HSP70 expression in fingerlings of the Indian major carp, Catla (Catla catla). Eight isonitrogenous and isoenergetic purified diets were formulated to contain graded levels of dietary phosphorus (dP), i.e., T₁, 0.1%; T₂, 0.3%; T₃, 0.5%; T₄, 0.7%; T₅, 0.9%; T₆, 1.1%; T₇, 1.3%; or T₈, 1.5%. Four hundred and eighty fish (average weight 4.23 ± 0.016 g) were equally distributed into 24 tanks forming eight treatments with three replicates each. The fish were fed daily at the rate of 3.5% body weight in two instalments. At the end of feeding trial fish were sampled to study total RBC and WBC count, haemoglobin, serum lysozyme activity, serum total protein, albumin (A), globulin (G) concentration and HSP70 expression. Total RBC count, haemoglobin concentration and serum lysozyme activity did not vary significantly in response to different dietary phosphorus concentrations. Total WBC count was found to be significantly (P < 0.05) higher in T₁ relative to all other treatments. Serum albumin and A/G ratio was found to be significantly lower in fish of T₁ and T₂ in relation to T₇ group (P < 0.05). Serum globulin and total protein levels remained unaffected by variations in dietary phosphorus. HSP70 expression was observed in T₁ group (0.1% dP) in gills and brain tissue, but not in liver and muscle tissues. No HSP70 expression was observed in fish of T₄ (0.7% dP) and T₈ (1.5% dP) treatments. These prima facie results suggest that dietary phosphorus had only minor influence on the haemato-biochemical parameters studied; however dietary phosphorus deficiency caused organ specific induction of HSP70 in catla fingerlings.     

Effects of sodium diformate on growth performance,gut microflora,digestive enzymes and innate immunological parameters of Asian sea bass (Lates calcarifer) juveniles

This study was conducted to evaluate the effects of dietary sodium diformate (NaDF) on growth performance, gut microflora, digestive enzyme activities and immune response parameters of Asian sea bass (Lates calcarifer) juveniles. Fish with initial weight of 12.5 ± 0.4 g were fed with five experimental diets contained 0.0 (control), 5, 10.0, 15.0 and 20 g NaDF kg^?1 in triplicate for 6 weeks. Fish fed diet containing 5 g NaDF kg^?1 had significantly the highest final body weight and feed intake among different treatments. The gut total viable bacterial counts gradually decreased with increasing dietary NaDF level. Specific activity of chymotrypsin improved in fish fed diets administered with NaDF compared to the control group. Fish fed 5 g NaDF kg^?1 diet showed the highest serum lysozyme level among different treatments. The serum classical pathway activity of complement showed higher level in fish fed diets contained 5 and 10 g NaDF kg^?1 than other groups. According to break‐point regression method analysis, the optimum inclusion of dietary NaDF in L. calcarifer juveniles was estimated between 4.6 and 5.1 g/kg, when specific growth rate and feed conversion ratio were plotted against dietary NaDF levels.     

Effects of dietary protein levels on the growth,body composition,serum biochemistry and digestive enzyme activity in Chinese rice field eel (Monopterus albus) fingerlings

A 12‐week feeding trial was conducted to determine the influence of dietary protein levels on growth performance, body composition, haematological parameters and digestive enzyme activity of Chinese rice field eel (Monopterus albus) fingerlings. Six isolipidic experimental diets (27.89%, 32.23%, 35.95%, 40.06%, 43.31% and 46.53%) were formulated to randomly assign to triplicate groups of 50 rice field eel fingerlings (5.0 ± 0.5 g) cultured in plastic cages. Results indicated that the best growth performance of fish with the highest WG (158.68 ± 31.59%) and SGR (2.28 ± 0.21%) was obtained at 40.06% group. Significant alterations were demonstrated on whole‐body crude protein, crude lipid and amino acid profile by different dietary protein levels. Besides, haematological parameters including triacylglycerol, aspartate aminotransferase and alkaline phosphatase decreased with various levels by the increasing of dietary protein levels. The lowest pepsin activity was observed in 27.89% protein group, which suggested lower availability of protein as substrate for protease activity. Meanwhile, the highest amylase activity in fish of 27.89% group indicated higher carbohydrate level in this group. Based on the polynomial regression analysis of WG and SGR, the dietary protein requirement for fingerlings of Monopterus albus was estimated to be 386.4–390.8 g/kg, respectively, with the lipid level of 10.08%.     

Dietary pyridoxine promotes growth and cellular metabolic plasticity of Chanos chanos fingerlings exposed to endosulfan induced stress

An attempt was made to assess the effect of dietary pyridoxine supplementation on growth performance and cellular metabolic enzymes of Chanos chanos fingerlings under endosulfan induced stress. Two‐hundred and twenty‐five fish were randomly distributed into five treatments, each with three replicates and fed four isocaloric and isonitrogenous diets with graded levels of pyridoxine for 45 days. Endosulfan concentration in the water was maintained at sublethal level of 1/40th of 96 h LC₅₀ (0.52 ppb). Dietary pyridoxine supplementation significantly enhanced growth performance viz. weight gain (%), specific growth rate, feed conversion ratio and protein efficiency ratio of fish compared to control diet fed group. The results of this experiment revealed that the activities of digestive and metabolic enzymes were significantly improved after feeding with dietary pyridoxine supplementation in C. chanos. Significantly increased muscle and brain ascorbic acid content was observed in fish fed diets containing pyridoxine. Histological studies on liver of fish fed pyridoxine‐supplemented diet showed the normal architecture of hepatocytes compared to non‐pyridoxine fed group. The results obtained in this study revealed that the inclusion of pyridoxine in diet has a protective effect against endosulfan induced stress in C. chanos fingerlings through metabolic enzyme activities and vitamin C content. This study has a potential in ameliorating the toxic effect of endosulfan induced stress using dietary supplementation of pyridoxine.     

Modulation of growth performances,survival, digestive enzyme activities and intestinal microbiota in common carp (Cyprinus carpio) larvae using short chain fructooligosaccharide

This study investigates the effects of inclusion of low levels of dietary short chain fructooligosacchairde (sc‐FOS) on physiological response and intestinal microbiota of carp (Cyprinus carpio) larvae. After acclimation, fish (550 ± 20 mg) were allocated into nine tanks (40 fish per tank) and triplicate groups were fed a control diet (0%) or diets containing 0.5% and 1% sc‐FOS for 7 weeks. At the end of the experiment, the growth performance parameters (final weight, weight gain, specific growth rate (SGR), food conversion ratio (FCR) and condition factor (CF), survival rate as well as digestive enzyme activities (amylase, lipase and protease), total viable counts of heterotrophic aerobic bacteria (TVC) and lactic acid bacteria (LAB) level in intestinal microbiota were measured. Our results revealed no significant (P > 0.05) effects of sc‐FOS on growth performance and TVC when compared with the control group. However, administration of low levels of dietary sc‐FOS significantly increased digestive enzyme activities (lipase and amylase) and LAB levels (P < 0.05). Also, survival rate was significantly elevated in sc‐FOS fed carp. These results revealed that administration of low levels of sc‐FOS can be considered as a beneficial dietary supplement for larval stage of common carp.     

Influence of dietary phosphorus on mineralization and morphology of Indian major carp,catla (<Emphasis Type="Italic">Catla catla</Emphasis>) fingerlings

The present study was conducted to investigate the changes in mineralization and morphology in response to graded levels of dietary phosphorus in Indian major carp, Catla (Catla catla) fingerlings (av. wt. 4.23 ± 0.87 g). The experimental system constituted of 24 150-L capacity plastic tanks (eight treatments, three replicates) stocked with 20 fingerlings each. Eight isonitrogenous and isocaloric semi-purified diets (crude protein 35%, crude lipid 8.5%) were formulated with graded levels of phosphorus (0%-control; 0.1; 0.3; 0.5; 0.7; 0.9; 1.1; 1.3; 1.5%) using KH₂PO₄. The fish were fed twice daily with the respective feeds for a period of 120 days. The percentage of ash content in whole body, vertebrae and opercular bones was found to be significantly (P < 0.05) lower in fish fed low levels of dietary phosphorus (T₁, T₂) in comparison with other treatments. The concentration of phosphorus and calcium was found to be significantly (P < 0.05) lower in whole body, vertebrae and opercula of fish fed low phosphorus diets (T₁, T₂) relative to treatments with higher levels of dietary phosphorus supplementation. The concentration of magnesium in opercular and vertebral tissues of T₁ group was significantly (P < 0.05) lower than all other groups. The X-ray radiographs did not reveal any skeletal deformities in any of the treatments. Truss analysis showed absence of significant morphological variations between fish of different treatments. The deficiency of dietary phosphorus in catla led to significantly lower mineralization of whole body and bone tissues, but the deficiency was not severe enough to cause skeletal deformities and morphological changes in the fish.     

A comparison of the effect of organic acids and dicalcium phosphate supplementation on phosphorus bioavailability,growth performance and digestive enzyme activities of Labeo rohita fingerlings

The effect of organic acids (OA) and dicalcium phosphate (P_i) supplementation in the feed of Labeo rohita fingerlings was studied by formulating seven practical diets, designed as D1 with no feed additives {dicalcium phosphorus (P_i) and organic acid (OA) blend} while, D2, D3, D4 and D5 were supplemented with P_i at the graded levels of 5, 10, 15 and 20 g/kg, respectively, whereas D6 and D7 contained blend of OA at 15 and 30 g/kg, respectively. The diet supplemented with OA blend exhibited increase (p < .05) in growth of L. rohita fingerlings compared with the diet supplemented with P_i. The OA supplementation at both levels showed significant improvement in nutrients digestibility and minerals absorption in fingerlings. Moreover, in case of muscle proximate composition, crude fat (CF) and crude protein (CP) were increased (p < .05) with the inclusion of OA blend in the diet while crude ash (CA) was improved by P_i supplementation. Additionally, digestive enzyme activities were not affected (p ? .05) by OA blend supplementation while increased activities were observed in the fingerlings fed with P_i diet. Consequently, supplementation of OA blend in the diet improved the growth performance and nutrient status while P_i enhanced digestive enzyme activities of L. rohita fingerlings.     

Effect of dietary taurine supplementation on growth performance,digestive enzyme activities and antioxidant status of juvenile black carp (Mylopharyngodon piceus) fed with low fish meal diet

An 8‐week feeding trial was conducted to determine the effects of dietary taurine supplementation on growth performance, activities of digestive enzymes, antioxidant status and the target of rapamycin (TOR) gene expression in black carp (initial body weight 5.94 ± 0.02 g) fed with low fish meal diet. Six isonitrogen and isolipidic diets were formulated. High fish meal–based diet (HFM) contained 20% fish meal and 24% soybean meal as a positive control. Fifty per cent of fish meal in HFM was replaced by soybean meal and were supplemented with 0, 0.05%, 0.1%, 0.2% and 0.4% dietary taurine respectively (designated as T_0.00 (a negative control), T_0.05, T_0.1, T_0.2 and T_0.4). The results showed that the partial replacement of fish meal by soybean meal without taurine supplementation resulted in a significant reduction in weight gain (WG), activities of amylase and lipase in intestine, superoxide dismutase (SOD) and glutathione peroxidase (GSH‐px) in serum, with a significant increase in feed conversion rate (FCR), the content of malonaldehyde (MDA), triglyceride (TG) and total cholesterol (TC) in serum. WG in groups supplemented with equal or above to 0.1% dietary taurine was significantly higher compared with T₀ group. With increasing levels of dietary taurine, the activities of amylase, lipase, GSH‐px and SOD and glutataione (GSH) content significantly increased (p < 0.05). FCR, the content of MDA, TG and TC in serum and crude lipid content in whole body were significantly reduced after taurine treatment (p < 0.05). In liver, TOR mRNA expression in groups with equal or above to 0.1% taurine was significantly higher than T₀ group (p < 0.05).     

The effects of dietary inulin and Jerusalem artichoke (Helianthus tuberosus) tuber on the growth performance,haematological, blood chemical and immune parameters of Nile tilapia (Oreochromis niloticus) fingerlings

This study investigated the effects of dietary inulin or Jerusalem artichoke (JA) on the growth performance, haematological, blood chemical and immune parameters of Nile tilapia fingerlings. Five treatment diets were designed to incorporate inulin at 0 (basal diet), 2.5 and 5.0 g/kg and JA at 5.0 and 10.0 g/kg. Two basal diets including fish meal and formulated experimental feed were used for fry and fingerling growing periods, respectively. During the fry growing period, larvae were fed treatment diets for 4 weeks. There were no significant differences in growth performance or survival rate. Fingerlings were then nursed with the formulated experimental diets from weeks 5 to 12. Fingerlings fed on inulin at 5.0 g/kg or JA at either level had better growth performance and survival rate than that fed on the basal diets. There were no significant differences in body composition. Dietary prebiotic inulin and JA increased red blood cell number (p < .05). Among the five blood chemistry parameters examined, both inulin at 5.0 g kg and JA (5.0 and 10.0 g/kg) increased blood protein (p < .05). Dietary inulin at 5.0 g/kg and JA at 5.0 and 10.0 g/kg increased total immunoglobulin and lysozyme activity (p < .05). Both inulin and JA inclusion diets increased alternative complement activity (p < .05). Taken together, dietary inulin at 5 g/kg and JA at 5.0 and 10.0 g/kg had beneficial effects on the growth performance, survival rate and immune of Nile tilapia fingerlings.     

Effect of oral administration of l -thyroxine (T4) on growth performance, digestibility, and nutrient retention in Channa punctatus (Bloch) and Heteropneustes fossilis (Bloch)

Effects of oral administration of l-thyroxine (T₄) on growth performance, body composition, and some aspects of nutritional physiology were investigated in two slow-growing air-breathing fish (Channa punctatus and Heteropneustes fossilis) under laboratory conditions (LD 12:12 at 25°C). The results indicate that irrespective of the species, fish fed diets containing lower doses of T₄ (up to 50 mg kg⁻¹ of diet in C. punctatus and up to 100 mg kg⁻¹ of diet in H. fossilis) showed significantly (P < 0.05) higher growth (in terms of live weight and length gain, specific growth rate, percentage gain in body weight and condition factor), low feed conversion ratio, high nutrient retention, high apparent protein digestibility, and high digestive enzyme activity. Viscero-somatic (VSI) and hepato-somatic (HSI) values were also high in fish fed on low dietary T₄ levels. Liver glycogen levels decreased with the increase in the dietary T₄ levels, indicating its utilization during growth. Muscle glycogen levels in H. fossilis coincided with high growth at 100 mg of T₄. Observation of the postprandial excretion of metabolites (N–NH₄ ⁺ and o-PO₄ ⁻) indicated significantly (P < 0.05) low levels in aquaria water where the fish were fed diets with low T₄ levels. These studies further revealed that feeding fishes on higher T₄ levels (above 50 mg in C. punctatus and above 100 mg in H. fossilis) not only repressed growth performance and nutrient retention, but also affected carcass composition by lowering protein accumulation (muscle and carcass protein) and energy assimilation. These studies revealed a biphasic action of thyroxine, i.e., the hormone at lower doses is anabolic, while at higher doses it acts as a catabolic agent, indicating that feeding fishes on higher doses can be detrimental to their growth and metabolism. In summary, the results of the present study show that feeding H. fossilis and C. punctatus on low doses of T₄ enhances growth, decreases excretion of metabolites, and increases nitrogen retention. These observations suggest that T₄ supplementation of the diet may have practical utility in the culture of slow-growing fish species.     

Effects of dietary 60 g kg−1 dried distiller's grains in least‐cost practical diets on production and gut allochthonous bacterial composition of cage‐cultured fish: comparison among fish species with different natural food habits

Dried distiller's grain (DDG) is considered as an alternative ingredient of dietary feed due to its high contents of protein, fibre and fat. In this study, 60 g kg^‐1 of DDG was used to feed grass carp (Ctenopharyngodon idella), bluntnose black bream (Megalobrama amblycephala), gibel carp (Carassius gibelio) and black carp (Mylopharyngodon piceus) for 8 weeks, and its effect on fish production and gut allochthonous microbiota was investigated for the development of a suitable fish feed high in nutrients and low in cost for polyculture freshwater fish. DDG supplementation resulted in the less weight gain and higher feed conversion ratio of black carp (P < 0.05), but had no significant effects on other fish or parameters. PCR–denaturing gradient gel electrophoresis (DGGE) analysis indicated that all four fish species had some common and unique bacteria in their digestive tracts, and the gut microbiota of bluntnose black and gibel carp fed the control diet and DDG diets were very similar (Cs > 91%); of them, the total counts of intestinal bacteria studied by qPCR increased in grass carp (P < 0.05) and depressed in black carp (P < 0.05) when fed dietary DDG. Thus, we assumed that dietary DDG modulated production and gut microbiota of fish in a host‐specific way.     

Effects of dietary orange peel on growth performance,antioxidant activity,intestinal microbiota and liver histology of Gilthead sea bream (Sparus aurata) larvae

This study investigated the effects of dietary orange peel (OP) on growth performance, feed utilization, antioxidant activity, intestinal microbiota and liver histology of Gilthead sea bream (Sparus aurata) larvae (0.32 ± 0.01 g/fish) (mean ± SD). Fish fed iso‐nitrogenous (480 g/kg protein) and iso‐energetic (23 MJ/kg) diets supplemented with OP at concentrations of 0, 1, 3 or 5 g/kg diet, for 60 days. Growth performance and feed utilization parameters were significantly improved by the elevation of dietary OP level, and the optimum level was 5 g/kg diet. The maximum activity of the total antioxidant capacity, superoxide dismutase, glutathione peroxidase, catalase, alkaline phosphatase enzyme and malondialdehyde in the liver was found at 5.5, 4.6, 3.4, 2.9, 3.7 and 3.8 g OP/kg diet, respectively. All tested bacteria (Staphylococcus spp., Vibrio spp. and Salmonela spp) and total bacterial count decreased significantly in the gut of fish fed high levels of OP (3.0 or 5.0 g/kg). No differences were found in the liver histo‐architecture among treatments after 60 days feeding on OP diets. In summary, dietary OP improved growth rate, antioxidant activity and intestinal microbiota of S. aurata larvae with an optimum range from 2.9 to 5.5 g/kg diet.     

Activities of digestive enzymes in relation to ingested natural food in three carp species of the Himalayan River Ladhiya,northern India

The present investigation was carried out to study gut content and accompanying digestive enzyme profiles of the three carp species, golden mahseer Tor putitora, snow trout Schizothorax richardsonii and hill trout Barilius barila. The fishes were captured from the River Ladhiya, Champawat district, Uttarakhand, northern India. The digestive tract length was on average 1.8 and 2.3 times longer than the body, while members of Bacillariophyceae, Chlorophyceae, Cyanophyceae and Zygnematophyceae made up 95.15% and 99.63% of gut content in the golden mahseer and snow trout, respectively. In hill trout, the digestive tract being only half the body length, gut content was insects (72.73%), eggs of aquatic organisms (22.73%) and nematodes (4.55%). Estimated gut enzyme activities demonstrated that amylase activity was significantly (P < 0.05) higher in golden mahseer and snow trout compared to hill trout, while total protease, trypsin and chymotrypsin activities were all significantly (P < 0.05) higher in the hill trout compared to other species. A strong co‐relation was found among relative gut length, food composition and digestive enzyme activities of each species. This may guide the future formulation of feed to these important species of carps kept in farm.     

Effects of dietary Bacillus and medicinal herbs on the growth, digestive enzyme activity, and serum biochemical parameters of the shrimp Litopenaeus vannamei

White shrimp (Litopenaeus vannamei) was fed six different formulations of medicinal herbs (MH) and Bacillus in a feeding trial conducted for 56 days. The survival, growth, digestive enzyme activity, and serum biochemical parameters were assessed. A basal diet without MH and Bacillus was served as the control. At the end of feeding trial, survival ranged from 76.19% to 84.76% with no significant differences (P > 0.05) among all groups. Growth measured as final weight, specific growth rate (SGR), protein efficiency ratio (PER), protein productive value (PPV), and feed efficiency ratio (FER) were improved with increased dietary MH and Bacillus. Shrimp fed 0.2% MH and 0.3% Bacillus (Diet 23) were found to have the best growth performance. For shrimp fed Diet 23 final weight and SGR were significantly (P < 0.05) higher than for controls. The digestive enzyme activity of protease and amylase in hepatopancreas and intestines were significantly (P < 0.05) enhanced by the feed supplements, however amylase of the hepatopancreas was not affected. Serum protein and glucose content were enhanced by the supplement of MH and Bacillus. Serum cholesterol in shrimp of high Bacillus level groups was significantly (P < 0.05) higher than in the control group. However, no significant difference (P > 0.05) in serum Triacylglycerols between supplemented groups and control was found. Results revealed that the combined MH and Bacillus in diet could enhance growth because it can improve digestive enzyme activity and digestive metabolism.     

Dietary ascorbic acid requirement for growth of striped catfish,Pangasianodon hypophthalmus (Sauvage, 1878) juveniles

A sixty‐day feeding trial was conducted to determine the ascorbic acid (AA) requirement for growth of striped catfish, Pangasianodon hypophthalmus juveniles. Seven iso‐nitrogenous and iso‐energetic (370 g protein per kg and 19.6 MJ/kg) purified diets were prepared with different levels of ascorbic acid such as control (0), T₁ (17.5), T₂ (35), T₃ (70), T₄ (175), T₅ (350) and T₆ (700) mg ascorbic acid (L‐ascorbyl‐2‐polyphosphate) equivalent per kg diet. Fish with a mean body weight of 3.2–3.4 g were stocked (fifteen fish per tank) in triplicates following a completely randomized design. Each group was fed to satiation twice a day for 60 days. Significant differences were observed in growth, survival, body composition and metabolic enzymes activities with different dietary ascorbic acid levels. Maximum weight gain, specific growth rate (SGR) and protein efficiency ratio (PER) were found in fishes fed with 35 mg AA per kg diet, supported by best feed conversion. Fish fed a diet containing vitamin C had the highest activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) compared to those fed with vitamin C‐depleted diets. In this study, based on using broken‐line regression analysis, the dietary vitamin C requirement for growth of P. hypophthalmus juveniles was estimated to be in the range of 46–76 mg AA per kg, depending on the criterion used, growth and liver storage. Our results will be helpful for the formulation of cost‐effective ascorbic acid incorporated diets for striped catfish, P. hypophthalmus.     

Immunomodulation and interferon gamma gene expression in sutchi cat fish,Pangasianodon hypophthalmus: effect of dietary fucoidan rich seaweed extract (FRSE) on pre and post challenge period

A 45‐days feeding trial was conducted to study the immunomodulatory effect and interferon gamma gene expression of dietary fucoidan rich seaweed extract (FRSE) from Sargassum wightii on Pangasianodon hypophthalmus fingerlings. One hundred and eighty fingerlings were distributed into six experimental groups in triplicates. Each group was stocked with 10 fish and fed to satiation with iso‐nitrogenous (34.96 ± 0.09–35.18 ± 0.03 CP%) and iso‐caloric (368.65 ± 0.86–375.09 ± 0.26 Kcal/100 g) purified diets containing either 0% FRSE (control), 1% FRSE (TF₁), 2% FRSE (TF₂), 3% FRSE (TF₃), 3% seaweed powder (TS₃) or 6% seaweed powder (TS₆) in the feed. After feeding trial the experimental fish were challenged with Aeromonas hydrophila. Immunological parameters like respiratory burst activity, lysozyme activity, phagocytic activity and total leukocyte count (TLC) were increased with the increasing level of dietary FRSE, whereas serum Albumin/Globulin (A/G) ratio and blood glucose level exhibited decreasing trend (P < 0.05). Increased TLC, blood glucose level, respiratory burst activity, serum A/G ratio, lysozyme and phagocytic activities were recorded during the post‐challenge period. Maximum expression of interferon gamma (IFN‐γ) gene was recorded in FRSE fed groups than the control group both in pre and post challenge condition. After challenged with A. hydrophila the highest survival was observed in TF₂ and TF₃ groups whereas lowest survival was observed in the control group. Hence, dietary supplementation of FRSE at an optimum level of 2% reduced the stress and improved the immune status of P. hypophthalmus fingerlings.