Effect of prebiotic mannan oligosaccharide on hematological and blood serum biochemical parameters of cultured juvenile great sturgeon (Huso huso Linnaeus, 1754)

The nutritional effects of prebiotic mannan oligosaccharide were evaluated using hematological and blood serum biochemical parameters in cultured juvenile great sturgeon (Huso huso). Fish were offered formulated diets containing two levels of prebiotic mannan oligosaccharide (2 and 4 g kg^?1); a basal diet with no prebiotics was used as control. The experiment lasted for 46 days. Blood samples were collected from the caudal veins of 18 apparently healthy fish (average weight 217.77 ± 29.8 g) at the end of the trial. No significant differences were found in the serum enzyme activity levels between treatments (P > 0.05). However, adding mannan oligosaccharide as a supplement to the basal diet resulted in significant differences in lymphocytes and eosinophils between the control and the 2 g kg^?1 treatment (P < 0.05) as well as a significant difference in the creatinine factor in the 2 g kg^?1 mannan oligosaccharide treatment (P < 0.05). The results show that it would be advantageous to add 2 g kg^?1 mannan oligosaccharide to the diets of juvenile great beluga sturgeon (Huso huso).     

Partial replacement of monocalcium phosphate with neutral phytase in diets for grass carp,Ctenopharyngodon idellus

A 9‐week experiment was designed to study the effects of partial replacement of monocalcium phosphate (MCP) with neutral phytase on growth, body compositions, serum biochemical statuses and intestinal digestive enzyme activities of grass carp, Ctenopharyngodon idellus. The control diet (designated as P2.0) was prepared with 2.0% MCP but without phytase. The three other diets (designated as PP1.5, PP1.0 and PP0.5, respectively) were supplemented with 1.5, 1.0 and 0.5% MCP, respectively, along with 500 FTU of neutral phytase kg^?1 diet in each. After a 9‐week feeding trial, fish (initial body weight: 43.44 ± 2.37 g) fed with PP1.5 and PP1.0 had no significant change in weight gain (WG), specific growth rate (SGR), protein efficiency rate (PER) or feed conversion ratio (FCR) compared with the control (P > 0.05) whereas fish fed with PP0.5 showed significantly lower growth performance in the above parameters. The crude lipid content in whole body or muscle of the fish fed with PP1.5 was significantly lower than the control while significantly higher in fish fed with PP0.5 (P < 0.05), whereas no obvious change was observed in the fish fed with PP1.0. For serum indices, higher serum alkaline phosphatase (Alkp), phosphorus (P) and calcium (Ca) contents were observed in fish fed with phytase‐supplemented diets in comparison with the control. In addition, dietary phytase supplementation increased amylase activity and decreased lipase activity in both foregut and hindgut. The present study suggests that dietary MCP can be reduced when neutral phytase is added to the grass carp diet, and that the maximum MCP reduction level can be up to 1% when neutral phytase is supplemented at 500 FTU kg^?1 diet.     

Effects of varying levels of dietary vitamin E (α‐tocopherol) on growth performance,proximate and fatty acid composition of juvenile silver pomfret (Pampus argenteus Euphrasen, 1788)

This study investigated the effects of elevated dietary levels of vitamin E (α‐tocopherol) on growth performance, proximate composition and fatty acid profiles of juvenile silver pomfret, Pampus argenteus. Three semi‐purified experimental diets were formulated to contain 49% protein and 16% lipid. High docosahexaenoic acid (DHA) tuna oil was added to the diets to supplement DHA. A graded level of vitamin E (0‐, 50‐, and 100 mg kg^?1) was added to experimental diets 1 to 3, respectively. Analyzed vit. E levels were 155.2, 195.3 and 236.4 mg kg^?1 in diets 1, 2 and 3, respectively. The experiment was conducted for 12 weeks with juvenile silver pomfret (29.6 ± 7.6 g) using a flow‐through system consisting of nine 1‐m³ tanks. Each treatment had three replicates and fish were stocked at the rate of 20 m^?3. Growth performance and feed utilization parameters of fish fed diets 2 and 3 were significantly (P < 0.05) higher than in fish fed diet 1, but the parameters in diets 2 and 3 did not differ significantly (P > 0.05). Although whole body protein levels were not influenced by the dietary vit. E levels, whole body lipid in fish fed diet 2 was significantly higher than in fish fed the other diets. The whole body vit. E levels in fish fed diet 2 (22.6 mg kg^?1) and diet 3 (24.1 mg kg^?1) were significantly (P < 0.05) higher than in those fed diet 1 (18.2 mg kg^?1). Whole body total saturated fatty acids were significantly lower, and DHA levels higher in fish fed diets 2 and 3 than those fed diet 1. The results of the present study suggest that increasing dietary supplementation of vit. E in high lipid diets enhances the growth performance of fish and that a dietary level of 196 mg kg^?1 vit. E is suitable for the growth of silver pomfret.     

Effect of dietary dextrin levels on the growth performance,blood chemistry,body composition,hepatic triglicerides and glycogen of Lebranche mullet juveniles (Mugil liza Valenciennes 1836, Mugilidae)

The effects of increasing levels of dietary dextrin on growth performance, body composition, blood chemistry and hepatic triglycerides and glycogen levels were evaluated for juvenile Lebranche mullet, Mugil liza Valenciennes 1836, Mugilidae). Five diets were formulated to be isonitrogenous (350 g kg^?1) and isolipidic (6 g kg^?1) with increasing dextrin levels (D150: 150 g kg^?1; D200: 200 g kg^?1; D250: 250 g kg^?1; D300: 300 g kg^?1; D350: 350 g kg^?1). The experimental diets were offered to the fish for 34 days, four times per day, until apparent satiation. Each treatment was tested in triplicate, with nine fish per tank (mean weight 4.69 ± 0.31 g). Fish were reared in a recirculating aquatic system of 15 fibreglass tanks each containing 50 L of saltwater. Growth parameters and body composition of the mullets were not significantly affected (P > 0.05) by the dietary treatments. Plasma glucose concentration declined (P < 0.05) when dietary dextrin increased from D250 to D300, but recovered to the previous values (in reference to D150 and D200) when fish were fed with D350. Glycated haemoglobin, plasma proteins, triglycerides and cholesterol showed no significant differences among these treatments. Hepatic glycogen reached a maximum in treatment D250, followed by D350, D200 and D300, with the lowest concentration of liver glycogen found in D150 (P < 0.05). The concentration of liver triglycerides showed an increase (P < 0.05) in treatments D300 and D350 compared with D200. In conclusion, Mugil liza juveniles can be fed diets with high levels of dietary dextrin with no deleterious effects to their growth or plasma biochemistry, hepatic glycogen or triglycerides.     

Coriolus versicolor polysaccharides enhance the immune response of crucian carp (Corassius auratus gibelio) and protect against Aeromonas hydrophila

To investigate the effect of Coriolus versicolor polysaccharides (CVPS) on the immune response of crucian carp (Corassius auratus gibelio), fish were fed diets containing CVPS at different concentrations including 0.5, 1.0 and 2.0 g kg^?1 for 5 weeks. Other groups of fish were vaccinated by intraperitoneal injection (i.p.) against Aeromonas hydrophila with a killed bacterin at the beginning of the experiment and fed the same diets as described above. Additionally, control fish and vaccinated‐only fish were fed basal diets without CVPS supplementation. The phagocytosis, lysozyme activity, complement components C3 and C4, E‐C3bRR (Erythrocyte‐C3b rosette rate) and E‐CIRR (Erythrocyte‐immune complex rosette rate) levels and circulating antibody titers in the serum were monitored. Five weeks after feeding the prescribed diet, fish were challenged with A. hydrophila and the mortalities recorded. Results showed that feeding non‐vaccinated and vaccinated crucian carp with CVPS stimulated the phagocytosis of leukocytes, lysozyme, complement components C3 and C4, erythrocyte immune adherence, and circulatory antibody titers in serum in vaccinated crucian carp. Immune parameters increased to their highest levels after 3 weeks of feeding the diet containing 0.5 or 1.0 g kg^?1 CVPS. These doses also resulted in the highest protection in the challenge experiment. Best survival (85%) was in the vaccinated group fed the diet containing 1.0 g kg^?1 CVPS, whereas almost 80% of control fish (negative control) and 50% of vaccinated‐only fish (positive control) died.     

Growth,parasitic infection and hematology in Colossoma macropomum Cuvier, 1818 fed diets containing Allium sativum

The aim of this study was to investigate the effects of a dietary Allium sativum (garlic) addition on growth, parasite infestation and blood parameters in Colossoma macropomum (tambaqui) using 12 net‐cages (1 m³). There were four treatments with three replicates each (15 fish per replicate). Tambaqui of 112.4 g mean weight were fed for 45 days with diets containing 0, 15, 30 and 45 g of fresh garlic kg^?1 feed. Garlic did not affect the tambaqui survival, growth, feed conversion, body condition, plasma glucose levels, total plasma protein levels or red blood cells. Total leukocyte and lymphocyte numbers decreased in fish fed diets containing 45 g garlic kg^?1 feed, but neutrophils decreased in fish fed diets containing 15, 30 and 45 g garlic kg^?1 diet, while the number of immature leukocytes increased in fish fed 30 g and 45 g garlic kg^?1diet. Gills in fish fed 30 and 45 g kg^?1 diet had lower infestation (52% and 63%, respectively) of Anacanthorus spathulatus (Monogenea) compared to controls. The application of garlic in diets improved the response of leukocytes and enhanced the resistance to infections by monogeneans.     

Evaluation of optimum dietary vitamin E requirements using DL‐α‐tocopheryl acetate in the juvenile eel,Anguilla japonica

The study aimed at evaluating the optimum dietary vitamin E requirements using DL‐α‐tocopheryl acetate in the juvenile eel, Anguilla japonica, as assessed by fish growth performance and fish body composition. Five semi‐purified experimental diets were formulated to contain 0 (TA₁), 15 (TA₁₇), 30 (TA₃₂), 60 (TA₆₂) and 120 (TA₁₁₉ mg TA kg^?1 diet on a dry matter (DM) basis in the form of DL‐α‐tocopheryl acetate (TA). After a 4‐week conditioning period, fish (15 ± 0.3 g) were randomly distributed into aquaria in groups of 20 at 25 ± 1.0°C (mean ± SD). One of the five diets was fed on a DM basis to fish in three randomly selected aquaria twice daily to satiation (approximately 3% of wet body weight per day at the beginning and 2% of wet body weight per day at the end of the feeding trial) for 12 weeks. At the end of the 12‐week feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) were determined; these were significantly lower in control fish than in fish fed supplemented diets (P < 0.05). The values for fish fed TA₁₇ were significantly higher than for fish fed TA₁, TA₆₂ or TA₁₁₉ (P < 0.05). There were no significant differences in WG, FE or PER among fish that were fed TA₁₇ and TA₃₂, among those that were fed TA₃₂ and TA₆₂, and among those that were fed TA₆₂ and TA₁₁₉ (P > 0.05). There were also no significant differences in SGR among fish fed TA₃₂, TA₆₂ or TA₁₁₉ (P > 0.05). A broken‐line regression analysis on the basis of WG, SGR, FE and PER showed that dietary vitamin E requirements of juvenile eels were 21.2, 21.6, 21.2 and 21.5 (mg kg^?1 diet), respectively. These results indicate that the dietary vitamin E requirement could be <21.2 mg kg^?1 but <21.6 mg kg^?1 diet in juvenile eel, A. japonica, when DL‐α‐tocopheryl acetate is used as the dietary vitamin E source.     

Effects of different concentrations of 2‐phenoxyethanol on primary and secondary stress responses in Persian sturgeon,Acipenser persicus

The anaethetic effects of 2‐phenoxyethanol (2‐PE) on possible primary (cortisol level) and secondary (hematological indices and glucose level) stress responses were studied in Persian sturgeon (Acipenser persicus). Fish were first exposed to 0.1, 0.3, 0.5, 0.7, 0.9 and 1.1 ml L^?1 2‐PE, and the time to induction (deep anaethesia) and recovery were measured. At a concentration of 0.1 ml L^?1, 2‐PE failed to induce deep anaethesia in fish, whereas at concentrations of 0.7, 0.9 and 1.1 ml L^?1 all fish were anaethetized within 3 min of exposure. For assessing possible stress effects caused by effective concentrations of 2‐PE, the hematological indices, serum cortisol and glucose were determined in the deeply anaethetized fish as stress indicators. The 2‐PE exposure resulted in significant increases in red blood cell (RBC) values at 0.3 and 0.5 ml L^?1; parallel increases in hemoglobin values were also observed at these concentrations (P < 0.01). Moreover, a lower concentration of 2‐PE (0.3 ml L^?1) caused a significant increase in hematocrit values (P < 0.05). Among the hematological indices, mean corpuscular volume (MCV) values decreased at 0.5 ml L^?1 when compared with the control and other groups (P < 0.05). Serum cortisol level was elevated at 0.3, 0.5 and 0.7 concentrations of 2‐PE (P < 0.01). The glucose level followed a trend similar to that observed for cortisol. The outcome of these experiments shows that 2‐PE at a concentration of 0.9 ml L^?1 is a suitable anaesthetic for Persian sturgeon. This study demonstrates that rapid induction of deep anaethesia with a relatively high concentration of 2‐PE (0.9 and 1.1 ml L^?1) was associated with the lowest effects on signs of physiological stress in Persian sturgeon.     

Dose‐response effects of the antioxidant α‐lipoic acid in the liver and brain of pompano Trachinotus marginatus (Pisces,Carangidae)

This study evaluated the effect of different doses of the antioxidant α‐lipoic acid (LA) administered by intraperitoneal injection on the detoxifying capacity (activity of glutathione‐S‐transferase, GST) and oxidative damage (lipids and proteins) in the pompano, Trachinotus marginatus. The plasma glucose levels showed that there were no differences between the treatments (P > 0.05). In the brain, GST activity was significantly higher (P < 0.05) in fish injected with 40 mg LA kg^?1 when compared with the control group. In the muscle, GST activity was not influenced by LA treatment (P > 0.05). In the liver, fish injected with 20 mg LA kg^?1 showed higher GST activity than the control group (P < 0.05); however, higher doses (40 and 60 mg LA kg^?1) led to a reduction of GST activity in the liver, which was comparable to that observed in the control group (P > 0.05). The two highest LA doses (40 and 60 mg kg^?1) had opposite effects, depending on the tissue examined: LA was an antioxidant in the brain, reducing lipid peroxidation (P < 0.05), and a pro‐oxidant in the liver, augmenting oxidative lipid damage (P < 0.05). The latter effect was accompanied by an increase in the free iron concentration in the liver at higher LA doses. These results indicate the need to thoroughly evaluate the antioxidant effects on aquatic organisms, since at some doses and/or in some organs their beneficial effects can be lost.     

Effect of cellulase,phytase and pectinase supplementation on growth performance and nutrient digestibility of rainbow trout (Oncorhynchus mykiss,Walbaum 1792) fry fed diets containing canola meal

This experiment was conducted to evaluate the effects of supplementing exogenous enzymes on growth, feed conversion ratio (FCR) and apparent nutrient digestibility in rainbow trout (Oncorhynchus mykiss) fry diets containing 32% canola meal. Five experimental diets (including a control diet containing no enzymes) were prepared as isonitrogenous (44% crude protein) and isocaloric (4000 kcal DE kg¹). The four other diets contained either cellulase, phytase, pectinase or an enzyme mix (a mixture of cellulase, phytase and pectinase in the same ratio). The feeding trial was conducted in triplicate for 12 weeks in 15 tanks (100‐L). At the beginning of the experiment 20 rainbow trout fry (initial weight 1.23 g) were stocked into each tank. Mean water temperature in the rearing tanks was 11°C and water flow in each tank was 6 L min^?1. At the end of the experiment the growth parameters and FCR displayed no significant differences in enzyme supplementation (P > 0.05). In addition, no differences were observed in dry matter, protein, or lipid digestibility with enzyme supplementation (P > 0.05). The results of this study showed that the addition of pectinase, phytase, cellulase or an enzyme mix to a diet containing 32% canola meal had no effect on growth, feed efficiency or dry matter, protein, or lipid digestibility in rainbow trout fry.     

Effect of dietary L‐malic acid supplementation on growth,feed utilization and digestive function of juvenile GIFT tilapia Oreochromis niloticus (Linnaeus, 1758)

Two feeding trials (FTs) were conducted in 2013 and 2014, respectively, to determine the optimal L‐malic acid (LMA) level for juvenile GIFT (Genetically Improved Farmed Tilapia) Oreochromis niloticus. Except for the LMA level, the FT1 and FT2 had a similar diet formulation. In FT1, LMA was included at 0 (basal diet), 1, 4, 8, 16 and 32 g kg^?1, respectively. After 20 weeks, daily weight gain and feed conversion ratio were improved but not differentiated with 1–8 g kg^?1 LMA. Further increasing the LMA supply initially decreased the feed intake (16 g kg^?1), and then decreased both feed intake and feed utilization (32 g kg^?1), thus impairing the fish growth. FT2 was subsequently conducted with a smaller LMA range (0, 0.5, 1, 2, 4 and 8 g kg^?1, respectively) but was unfortunately terminated at the end of 8 weeks because 20% of the fish were badly injured during weighing. Unexpectedly, growth and feed utilization were still improved but not differentiated with 0.5–8 g kg^?1 LMA. In FT2, beneficial effects of LMA inclusion on the digestive function (pepsin, foregut amylase and foregut lipase), the activities of serum lysozyme and hepatic superoxide dismutase, and liver lipid peroxidation (malondialdehyde concentration) were found. Taking the results of FT1 and FT2 together, it could be concluded that dietary LMA supplementation at low concentrations (0.5–8 g kg^?1) could improve growth and feed utilization, but excess LMA (≥16 g kg^?1) might compromise feed intake and/or feed utilization, thus impairing fish growth. To reduce feed costs in commercial practice, 0.5 g kg^?1 LMA is recommended in the feed of juvenile GIFT tilapia based on the results of this study.     

Dietary Supplementation of Zinc Nanoparticles and Its Influence on Biology,Physiology and Immune Responses of the Freshwater Prawn,Macrobrachium rosenbergii

The present study was conducted to assess the influence of dietary zinc nanoparticles (size 50 nm) on the growth, biochemical constituents, enzymatic antioxidant levels and the nonspecific immune response of the freshwater prawn, Macrobrachium rosenbergii post larvae (PL). The concentrations of dietary supplement zinc nanoparticles (ZnNPs) were 0, 10, 20, 40, 60 and 80 mg kg^?1 with the basal diet, and the level of Zn in ZnNP-supplemented diets were 0.71, 10.61, 20.73, 40.73, 60.61 and 80.60 mg kg^?1, respectively. ZnNP-incorporated diets were fed to M. rosenbergii PL (initial body weight, 0.18?±?0.02 g) in a triplicate experimental setup for a period of 90 days. ZnNP supplemented feed fed PL up to 60 mg kg^?1 showed significantly (P?<?0.05) improved performance in survival, growth and activities of digestive enzymes (protease, amylase and lipase). The concentrations of biochemical constituents (total protein, total amino acid, total carbohydrate and total lipid), total haemocyte count and differential haemocyte count were elevated in 10–60 mg kg^?1 ZnNP supplemented feed fed PL. However, the PL fed with 80 mg ZnNPs kg^?1 showed negative results. Activities of enzymatic antioxidants [superoxide dismutase (SOD) and catalase (CAT)], metabolic enzymes [glutamate–oxaloacetate transaminase (GOT) and glutamate–pyruvate transaminase (GPT)] and the process of lipid peroxidation (LPO) in the hepatopancreas and muscle showed no significant alterations in 10–60 mg kg^?1 ZnNP supplemented feed fed PL. Whereas, 80 mg ZnNPs kg^?1 supplemented feed fed PL showed significant elevations in SOD, CAT, LPO, GOT and GPT. Therefore, 80 mg ZnNPs kg^?1 was found to be toxic to M. rosenbergii PL. Thus, the study suggests that up to 60 mg ZnNPs kg^?1 can be supplemented for regulating survival, growth and immunity of M. rosenbergii.     

Effects of dietary thymol‐carvacrol on growth performance,hematological parameters and tissue composition of juvenile rainbow trout,Oncorhynchus mykiss

Growth performance, carcass quality, survival and hematological responses of Oncorhynchus mykiss juveniles (initial weight 8.4 ± 0.1 g) fed diets containing thymol‐carvacrol powder at the levels of 0, 1.0, 2.0, 3.0 g kg^?1 were tested. Thymol‐carvacrol powder originated from Origanum vulgare, a Mediterranean plant, added to diets. Each diet was fed to triplicate groups of fish for 45 days. Fish fed diets containing thymol‐carvacrol had significantly higher final weight and growth than the control group. Food conversion ratio in fish fed diets containing 2.0 and 3.0 g kg^?1 thymol‐carvacrol was statistically better than in other treatments. Survival was not different among all treatments. The number of lymphocytes increased when thymol‐carvacrol was used at higher levels. Furthermore, whole body lipid content was higher in fish fed 1.0 and 2.0 g kg^?1 thymol‐carvacrol than the other groups, but body protein in the group fed 3.0 g kg^?1 was higher than in other groups. Also, body ash in control and 1.0 g kg^?1 was higher than in other groups. Whole body dry matter was not affected by dietary treatments. These results indicated that dietary administration of thymol‐carvacrol can influence some growth, hematological parameters and tissue composition in rainbow trout juveniles.     

Effects of β‐xylanase and 6‐phytase on digestibility,trace mineral utilisation and growth in juvenile red tilapia,Oreochromis niloticus (Linnaeus, 1758) x O. mossambicus (Peters, 1852), fed declining fishmeal diets

In response to the global sustainability drive to lower fishmeal (FM) inclusion in aquatic feeds, exogenous enzymes can improve nutrient digestibility in monogastric plant‐based diets. A 80‐day experiment was conducted to evaluate the combined effects of xylanase and phytase on digestibility, trace mineral utilisation and growth in juvenile red tilapia, Oreochromis niloticus x O. mossambicus, (48.8 g ± 13.9; μ ± STD) fed declining FM diets. Basal diets were formulated to contain 0, 3 and 5% FM with and without xylanase (0.385 g kg^?1) and phytase (0.075 g kg^?1), forming six treatments. Each treatment was randomly assigned to four replicates, 20 fish tank^?1; mean water temperature 28.98 ± 0.73°C. Although the size of the effects was modest, growth performances (feed intake, FCR, growth rate) decreased with lower FM levels (P < 0.05) but improved with enzyme supplementation. Enzyme supplementation increased P digestibility and trace mineral uptake (P < 0.05), but no effects were seen on protein digestibility and N retention. Nevertheless, tilapia fed the enzyme‐supplemented 3% FM and control 5% FM diets performed comparably (P < 0.05). This potentially justifies a 2% FM reduction for tilapia diets using exogenous xylanase and phytase without significant effects on digestibility, trace mineral utilisation and growth.     

Immune responses and intestinal morphology of striped catfish,Pangasianodon hypophthalmus (Sauvage, 1878), fed dietary nucleotides

The present study was conducted to evaluate the effects of dietary nucleotides (NT) on growth performance, immune responses, and intestinal morphology of striped catfish, Pangasianodon hypophthalmus. Different levels of NT (0, 0.25. 0.5, 0.75, and 1% weight per weight, WW^?1) were used in the basal diet and then randomly allocated to triplicate groups of fish with an average initial weight of 1.52 ± 0.11 g for 10 weeks. Nucleotide supplementation did not improve growth parameters significantly (P > 0.05). Feeding fish with a NT‐containing diet significantly improved ACH₅₀ activity and IgM levels in comparison to the control group (P < 0.05). The dietary NT (P < 0.05) affected the intestinal morphology, whereby the folds and enterocyte heights in the mid‐intestine were significantly increased compared to the control group (P < 0.05), while the microvilli length was not affected. The results indicate that feeding striped catfish with commercial NT have significant effects on the immune parameters and intestinal morphology of catfish and that the best NT levels are 0.25 and 0.5%.     

Dietary total aromatic amino acid requirement and tyrosine replacement value for phenylalanine in Indian major carp: Cirrhinus mrigala (Hamilton) fingerlings

Two 8‐week growth trials were conducted to determine total aromatic amino acid requirement and tyrosine replacement value for phenylalanine in Cirrhinus mrigala fingerlings. To determine the phenylalanine requirement, 20 fish were randomly stocked in triplicate groups in 55‐L indoor polyvinyl flow‐through circular tanks and fed six experimental diets containing graded levels of phenylalanine (5.0, 7.5, 10.0, 12.5, 15.0 and 17.5 g kg^?1, dry diet) with 10 g kg^?1 tyrosine. Maximum weight gain (287%), best FCR (1.44) and PER (1.74) occurred at 12.5 g kg^?1 dietary phenylalanine. Quadratic regression analysis of weight gain, FCR and PER data indicated phenylalanine requirement at 13.5, 12.9 and 12.7 g kg^?1 of dry diet, respectively. Protein deposition was significantly (P < 0.05) higher at 12.5 g kg^?1 dietary phenylalanine. Based on the above results, phenylalanine requirement of C. mrigala is recommended at 13.0 g kg^?1 of dry diet, corresponding to 32.5 g kg^?1 of protein. On the basis of the above requirement, a second experiment with a similar design was conducted using six diets containing graded levels of tyrosine (2.1, 4.0, 6.0, 8.0, 10.0 and 12.0 g kg^?1) with 13.0 g kg^?1 phenylalanine fixed in all diets to determine the phenylalanine replacement value with that of tyrosine. Maximum weight gain (315%), best FCR (1.47) and PER (1.69) was at 8.0 g kg^?1 dietary tyrosine. Quadratic regression analysis of weight gain, FCR and PER data indicated tyrosine requirement at 9.0, 8.4 and 8.2 g kg^?1 of dry diet, respectively. Protein deposition was significantly (P < 0.05) higher at 8.0 g kg^?1 dietary tyrosine. On the basis of the above results, 8.5 g kg^?1 tyrosine, corresponding to 21.3 g kg^?1 of protein, is taken as the optimum requirement and the replacement value is 39.53% on a weight and 36% on a molar basis. Thus, the total aromatic amino acid requirement is 21.5 g kg^?1 of diet, corresponding to 53.8 g kg^?1 of protein for optimum C. mrigala growth.     

Dietary administration of chitooligosaccharides to enhance growth, innate immune response and disease resistance of Trachinotus ovatus

The present study was conducted to investigate the effects of dietary chitooligosaccharides (COS) supplementation on the innate immune response and protection against Vibrio harveyi infection in Trachinotus ovatus. A basal diet was supplemented with 0.0 (control), 2.0, 4.0 and 6.0 g COS kg^?1 to formulate four experimental diets. Each diet was randomly allocated to triplicate groups of ?sh in ?oating sea cages (1.5 × 1.0 × 2.0 m), and each cage was stocked with 80 ?sh (initial average weight 10.8 ± 0.05 g). After 8 weeks of feeding trial, Both the final weight and specific growth rate (SGR) signi?cantly increased with increasing dietary COS levels up to 4.0 g kg^?1, whereas there were no signi?cant differences for COS levels from 4.0 to 6.0 g kg^?1. A decreased feed conversion ratio (FCR) was observed with increasing dietary COS levels. The total leukocyte counts (WBC), differential leukocyte counts, respiratory burst activity, lysozyme and superoxide dismutase (SOD) activity were signi?cantly increased with the increased levels of dietary COS (P < 0.05), and reached a maximum at level of 4.0 g kg^?1 COS. There were no signi?cant differences in those immunological parameters between 4.0 and 6.0 g kg^?1 COS. Moreover, the dietary COS supplementation groups also exhibited a decrease in the cumulative symptom rates compared to the controls when challenged with V. harveyi. These results indicated that dietary intake containing COS could enhance the immune responses of fish and improve its resistance to infection by V. harveyi. Especially supplementation with 4.0 g kg^?1 COS to the fish for 56 days showed considerable improvement in the growth, survival and immune response of the fish.     

Immunostimulating effect of triiodothyronine: dietary administration of triiodothyronine in rohu (Labeo rohita) enhances immunity and resistance to Aeromonas hydrophila infection

The immunomodulatory effects of dietary administration of 3,3^′,5‐triiodo‐l ‐thyronine (T₃) at 0, 1, 5 and 10 mg  kg^?1 of diet for 60 days in rohu (Labeo rohita) fingerlings were studied. Oral administration of T₃ at all dose levels resulted in significantly (P<0.05) higher serum T₃ levels, total serum protein and globulin levels, and reduced albumin–globulin ratio (A : G) compared with the control group, whereas feeding of T₃ at 5 and 10 mg kg^?1 diet enhanced the growth and superoxide production by neutrophils. At the end of the 60‐day experimental period the optimum dosage of T₃ appeared to be the 5 mg  kg^?1 diet for rohu fingerlings, resulting in a significantly higher specific antibody titre against formalin‐killed Aeromonas hydrophila and lowering the mortality percentage against the A. hydrophila challenge.     

Influence of Tribulus terrestris extract on the survival and histopathology of Oreochromis mossambicus (Peters, 1852) fry before and after Streptococcus iniae infection

The aim of this study was to determine the effects of Tribulus terrestris extract (TT) on growth performance, disease resistance and histopathological changes in intestine and liver tissues of Oreochromis mossambicus (Peters, 1852) first‐feeding fry before and after exposure to Streptococcus iniae. Five isonitrogenous and isocaloric diets were formulated to contain 0 (control), 200, 400, 600, and 800 mg kg^?1 TT. After feeding for 45 days, fish were infected with S. iniae and mortalities recorded. Final weight, weight gain and SGR of tilapia fry fed the 400 mg kg^?1 TT diet were significantly greater than that of control diet. In the challenge experiment, the best survival rate was obtained with 400 mg kg^?1 TT supplementation. Infection by S. iniae appeared to have a negative effect on histopathological findings and outcome than did TT‐800 used alone. However, administration of TT (200 or 400 mg extract kg^?1) resulted in overall improvement in the intestine and liver histopathology, emphasizing the protective potential of TT. The present study suggests the protective potential of TT in alleviating intestinal and hepatic damage that can occur after a S. iniae infection. It was concluded that 400 mg kg^?1 TT can enhance growth and disease resistance during first–feeding of O. mossambicus fry. This suggests that TT may be an alternative to antibiotics in controlling streptococcal disease in tilapia culture.     

Immunomodulatory effect of sodium alginate enriched diet in kelp grouper Epinephelus brneus against Streptococcus iniae

The effect of diets containing sodium alginate at 0, 0.5, 1.0, and 2.0 g kg^?1 following challenge with Streptococcus iniae in kelp grouper Epinephelus bruneus were assessed with reference to survival rate and innate immune parameters such as alternative complement, lysozyme, natural haemagglutination, respiratory burst, superoxide dismutase, and phagocytic activities on week 1, 2, and 4. Fish fed with sodium alginate containing diet at 1.0 and 2.0 g kg^?1 after being challenged with S. iniae had higher survival rates of 75% and 60%, respectively than those fed with control diet (0 g kg^?1). With any enriched diet the percentage of macrophages significantly decreased from week 1–4, while the percentage of neutrophils and lymphocytes significantly increased. The alternate complement activity, natural haemagglutination, and phagocytic activities of infected fish fed with sodium alginate containing diet at 1.0 g kg^?1 on week 2 and 1.0 and 2.0 g kg^?1 diets on week 4 were significantly higher when compared to the control. The lysozyme, respiratory bursts, and superoxide dismutase activities of fish fed with enriched diets at 1.0 and 2.0 g kg^?1 were significantly increased on week 2 and 4. We therefore recommend that at 1.0 or 2.0 g kg^?1 dietary administration of sodium alginate can enhance innate immunity and disease resistance in kelp grouper against S. iniae.