Dietary thiamin requirement of fingerling Channa punctatus (Bloch) based on growth,protein gain,liver thiamin storage,RNA/DNA ratio and biochemical composition

Dietary thiamin requirement of fingerling Channa punctatus was quantified by feeding casein/gelatin‐based diets (450 g/kg CP; 18.39 kJ/g GE) with seven graded levels of thiamin (0, 0.5, 1, 1.5, 2, 2.5 and 5 mg/kg diet) to triplicate groups of fish (6.9 ± 0.93 cm; 4.91 ± 0.62 g) for 16 weeks. Fish fed diet with 2.5 mg/kg thiamin reflected highest absolute weight gain (AWG), protein gain (PG), RNA/DNA ratio and lowest feed conversion ratio. Similarly, highest liver thiamin concentration was also recorded in fish fed 2.5 mg/kg thiamin diet. Hepatic thiobarbituric acid reactive substance (TBARS) concentration responded negatively with increasing concentrations of dietary thiamin up to 2.5 mg/kg, whereas superoxide dismutase and catalase activities were found to improve with the increasing levels of dietary thiamin from 0 to 2.5 mg/kg. Transketolase activity also improved as the thiamin concentrations increased up to 2.5 mg/kg. Broken‐line regression analysis of AWG, PG, RNA/DNA ratio, liver thiamin concentrations, transketolase and TBARS activities exhibited the thiamin requirement in the range of 2.34–2.59 mg/kg diet. Data generated during this study would be useful in formulating thiamin‐balanced feeds for the intensive culture of this fish.     

Dietary pantothenic acid requirement of fingerling Channa punctatus (Bloch) based on growth,feed conversion,liver pantothenic acid concentration and carcass composition

A 16‐week feeding trial was conducted to determine the dietary pantothenic acid requirement of fingerling Channa punctatus. Six casein–gelatin‐based diets (450 g/kg CP; 18.39 kJ/g GE) with graded levels of pantothenic acid (0, 10, 20, 30, 40 and 50 mg/kg diet) were fed to triplicate groups of fish (6.2 ± 0.71 cm; 4.26 ± 0.37 g) near to apparent satiation. The growth evaluation in terms of absolute weight gain (AWG), feed conversion ratio (FCR) and protein retention efficiency (PRE) indicated the best performance (p < .05) in fish fed diet containing 30 mg/kg pantothenic acid. Highest haemoglobin, haematocrit and RBCs counts were also obtained in fish fed diet with 30 mg/kg pantothenic acid. Mean cell haemoglobin and mean cell volume were found to be lowest in fish fed pantothenic acid‐free diet indicating the anaemia in this group of fish. Superoxidase dismutase and catalase activities of liver tissue were found to improve (p < .05) with the increasing levels of dietary pantothenic acid from 0 to 30 mg/kg. However, liver pantothenic acid concentration responded positively with the increasing levels of pantothenic acid up to 40 mg/kg diet and then stagnation in liver pantothenic acid concentration with the further inclusion of pantothenic acid was recorded. Second‐degree polynomial regression analysis of AWG, FCR and PRE exhibited the pantothenic acid requirement at 36.4, 32.8 and 34.7 mg/kg diet, respectively. Data generated during this study would be useful in formulating pantothenic acid‐balanced commercial feeds for the intensive culture of this fish.     

Dietary folic acid requirement of fingerling Catla,Catla catla (Hamilton)

The dietary folic acid requirement of fingerling Catla catla (3.4 ± 0.17 g; 7.6 ± 0.41 cm) was evaluated by feeding casein–gelatin‐based isonitrogenous (350 g/kg crude protein) and isocaloric (16.72 kJ/g GE) diets containing different concentrations of folic acid (0, 0.2, 0.4, 0.6, 0.8, 1.0, 2.0 mg/kg) to triplicate groups to apparent satiation at 08:00, 12:30 and 17:30 hr for 16 weeks. Absolute weight gain (AWG; 40.07 g/fish), specific growth rate (SGR; 2.25%), feed conversion ratio (FCR; 1.53), protein retention efficiency (PRE; 31.42%) and protein gain (PG; 6.74) improved significantly (p < .05) with increasing folic acid levels up to 0.4 mg/kg diet and then reached a plateau. However, maximum liver folic acid concentration increased up to 0.6 mg/kg diet. Dietary folic acid levels also significantly affected (p < .05) body composition of fish. No significant change (p > .05) in haematological parameters except in fish fed folic acid‐free diet was noted. Antioxidant and immune parameters increased with increasing concentration of dietary folic acid up to 0.4 mg/kg diet. Broken‐line regression analysis of AWG, FCR, PRE, PG, HCT and liver folic acid concentrations of fingerling C. catla against dietary folic acid levels indicated optimum growth, FCR, PRE, PG, HCT and liver folic acid saturation ranging between 0.22 and 0.56 mg/kg diet, respectively.     

Dietary pyridoxine requirement of fingerling Channa punctatus (Bloch) based on growth performance,liver pyridoxine concentration,and carcass composition

Seven casein gelatin-based diets containing 450 g/kg CP and 18.39 kJ/g GE with different levels of pyridoxine (0, 2, 4, 6, 8, 10, and 12 mg/kg diet) were fed to fingerling Channa punctatus (4.66 ± 0.46 g) for 12 weeks to determine pyridoxine requirement. Highest absolute weight gain (AWG; 25.81 g/fish, P < 0.05), protein retention (PRE; 23.69%, P < 0.05), energy retention efficiencies (ERE; 69.63%, P < 0.05), and minimum feed conversion ratio (FCR; 1.48) were noted at 8 mg pyridoxine/kg diet. However, liver pyridoxine content achieved the positive correlation as the dietary pyridoxine increased up to 10mg/kg. On the basis of broken-line analysis of AWG, PRE, FCR, and liver pyridoxine data, pyridoxine requirement is recommended between 7.6 and 10.4 mg/kg of dry diet.     

Effect of dietary isoleucine level on growth,protein retention efficiency,haematological parameter,lysozyme activity and serum antioxidant status of fingerling Channa punctatus (Bloch)

Isoleucine requirement of fingerling Channa punctatus (6.74 ± 0.09 g) was estimated by feeding seven trial diets (450 g/kg CP, 14.73 kJ/g DE) containing 3.8, 7.5, 11.3, 15.1, 19.3, 23.2 and 27.4 g/kg of isoleucine for 12 weeks. Growth and haematological parameters increased with the increasing concentrations of dietary isoleucine up to 16 g/kg. Carcass protein and fat increased significantly with the increasing concentrations of dietary isoleucine up to 16 g/kg and then stabilized. Moisture content showed reverse trend to that of carcass fat. Hepatosomatic index was found to be highest at 4 g/kg of dietary isoleucine. Viscerosomatic index and condition factor increased significantly with increasing levels of isoleucine up to 16 g/kg dry diet. Serum protein, lysozyme and superoxide dismutase activities were also found to increase significantly up to 16 g/kg dry diet. Significant reduction in alanine aminotransferase and aspartate aminotransferase activities was observed by increasing concentrations of dietary isoleucine up to 16 g/kg. Based on quadratic regression analysis of absolute weight gain, feed conversion ratio, protein retention and isoleucine retention efficiencies against varying concentrations of isoleucine, the optimum isoleucine requirement ranging between 17.95 and 18.39 g/kg dry diet, corresponding to 39.88–40.86 g/kg dietary protein, is recommended for maximizing growth of C. punctatus.     

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.     

Determination of dietary phosphorus requirement of stinging catfish Heteropneustes fossilis based on feed conversion,growth, vertebrae phosphorus,whole body phosphorus,haematology and antioxidant status

A 12‐week feeding trial was conducted to determine the dietary phosphorus requirement of Heteropneustes fossilis fingerlings (7.7 ± 0.04 g). Fish were fed casein–gelatine‐based purified diets in triplicate groups near satiation with seven different levels of dietary phosphorus (3.2, 5.2, 7.2, 9.2, 11.2, 13.2 and 15.2 g/kg dry diet). All diets were formulated to be isoproteic (400 g/kg) and isoenergetic (17.89 kJ/g). Highest absolute weight gain (68.38 g/fish), best feed conversion ratio (1.48), protein retention efficiency (30.74%), protein gain (12.44 g/fish), haemoglobin (11.19 g/dL), RBCs (3.12 x10⁶/mm³), haematocrit (33.44%) and serum phosphate (2.82 mg/L) were found at 9.2 g/kg phosphorus. Hepatic superoxide dismutase and catalase activity were also significantly influenced by the dietary phosphorus levels. Whole body and vertebrae phosphorus concentrations increased significantly as the amount of dietary phosphorus increased from 3.2 to 11.2 g/kg dry diet and then plateaued. More accurate information on dietary phosphorus requirement was obtained by subjecting the AWG, FCR, vertebrae phosphorus and whole body phosphorus concentrations data against various levels of dietary phosphorus to broken‐line analysis, which yielded the requirement in the range of 9.0–11.0 g/kg for optimum growth and mineralization of H. fossilis.     

Dietary Vitamin C Requirement of Fingerling,Cirrhinus mrigala (Hamilton), Based on Growth,Feed Conversion,Protein Retention,Hematological Indices,and Liver Vitamin C Concentration

This study was conducted to quantify dietary vitamin C requirement of fingerling, Cirrhinus mrigala, (0.79 ± 0.07 g; 3.51 ± 0.15 cm) by feeding casein‐gelatin based purified diets (400 g/kg crude protein; 3.45 kcal/g digestible energy) containing nine levels of vitamin C as l‐ascorbyl‐2‐polyphosphate (0.0, 5, 15, 25, 35, 45, 55, 75, and 95 mg vitamin C equivalent/kg diet) to triplicate groups of fish to apparent satiation for 16 wk. Absolute weight gain (AWG, g/fish), feed conversion ratio (FCR), protein retention efficiency (PRE%), RNA/DNA ratio, hemoglobin (Hb, g/dL), and hematocrit value (Hct%) were taken as the response criteria to determine vitamin C requirement of mrigal. Fish fed diet with 35 mg/kg vitamin C had significantly higher AWG (9.94 g/fish), FCR (1.39), PRE (27.72%), RNA/DNA ratio (4.18), Hb (11.15 g/dL), and Hct (34.44%) values. However, liver vitamin C concentration was found to be higher (64.92 µg/g wet tissue) in diet containing 45 mg vitamin C/kg. Broken‐line regression analysis of AWG data estimated the requirement of 35.65 mg/kg, whereas that of the liver vitamin C concentration data projected the requirement to 41.99 mg/kg.     

Dietary copper requirement of fingerling Heteropneustes fossilis for formulating copper‐balanced commercial feeds

Dietary copper requirement of Heteropneustes fossilis (6.74 ± 0.03 g) was determined by feeding purified diets containing same protein (400 g/kg) and gross energy (17.89 kJ/g) but different levels of copper for 12 weeks. Graded amount of CuSO₄.5H₂O (0, 1.96, 3.93, 5.89, 7.86, 9.82, 11.79 mg/kg) was supplemented to basal diet to attain desired dietary copper levels (0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mg/kg). Analysed dietary copper concentrations were 4.28, 4.63, 5.28, 5.70, 6.19 and 6.69 mg/kg. Absolute weight gain, feed conversion ratio and protein gain improved with the increasing levels of dietary copper up to 5.28 mg/kg. Further inclusion of copper at a level of 5.70 mg/kg did not improve the above parameters. Significantly higher (p < .05) plasma ceruloplasmin, liver copper‐zinc superoxide dismutase, catalase activities and lower thiobarbituric acid reactive substances were evident in fish receiving diets with 5.28 and 5.70 mg/kg copper compared to other groups. Whole body and liver copper concentrations increased significantly (p < .05) with increasing dietary copper levels. Quadratic regression analysis of absolute weight gain, feed conversion ratio, protein gain and broken‐line regression analysis of plasma ceruloplasmin activity and liver TBARS value against the variable dietary copper levels depicted the dietary copper requirements for fingerling H. fossilis in the range of 5.24–5.68 mg/kg.     

Dietary protein requirement for fingerling Channa punctatus (Bloch), based on growth, feed conversion, protein retention and biochemical composition

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

Quantitative dietary copper requirement of juvenile Siberian sturgeon,Acipenser baerii,and effects on muscle composition and some enzymatic activities

An 8‐week feeding trial was conducted to quantify dietary copper (Cu) requirement of juvenile Siberian sturgeon, Acipenser baerii. Five isonitrogenous diets were formulated to provide actual dietary copper values of 1.8, 5.7, 10.1, 15.9 and 28.3 mg Cu per kg diet. Experimental diets were fed to the Siberian sturgeon (27.57 ± 0.24 g) in triplicate to apparent satiation for 8 weeks. At the end of experiment, weight gain (WG), specific growth rate (SGR) and protein efficiency ratio (PER) were significantly increased with increasing dietary Cu level up to 10.1 mg/kg and then decreased with further increases in dietary Cu level (p < .05). The Cu concentration in the liver and cartilage was positively correlated with the respective concentrations in the diet (p < .05), while muscle and serum Cu concentrations remained significantly unchanged (p > .05). Superoxide dismutase and glutathione peroxidase had the highest activities in serum of fish fed with 15.9 and 28.3 mg Cu per kg diet, respectively. Analysis by the broken‐line regression of SGR, crude protein content and superoxide activity demonstrated that the optimum dietary Cu requirements in juvenile Siberian sturgeon were 9.51, 9.58 and 16.10 mg/kg diet, respectively.     

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 Biotin Requirement of Fingerling Catla catla (Hamilton) Based on Growth,Feed Conversion Efficiency,and Liver Biotin Concentration

A 12‐wk experiment was conducted to determine the dietary biotin requirement of the fingerling Catla catla (7.9 ± 0.37 cm; 3.5 ± 0.12 g). Eight diets (35% crude protein, 16.72 kJ/g gross energy) with different levels of biotin (0, 0.05, 0.1, 0.5, 1.0, 1.5, 2.0, and 2.5 mg/kg diet) were fed to triplicate groups of fish to apparent satiation. Highest percent weight gain, protein retention efficiency, and best feed conversion ratio were observed in fish fed 0.5 mg biotin per kg diet. However, fish fed diets containing dietary biotin of 1.0, 1.5, 2.0, and 2.5 mg/kg did not show significant (P > 0.05) differences compared to those fed on dietary biotin of 0.5 mg/kg. Hematological indices, including hematocrit value, hemoglobin content, and red blood cell counts were found to be directly proportional (P < 0.05) to the dietary biotin levels up to 0.5 mg/kg, beyond which a plateau was recorded. Pyruvate carboxylase activity (PCA) was also found to increase with the incremental levels of dietary biotin up to 0.5 mg/kg and further increasing dietary biotin concentration led to stagnation in PCA of fish. Liver biotin concentrations responded positively (P < 0.05) until saturation, which occurred at 1.0 mg/kg diet. Broken‐line analysis of percent weight gain, protein retention efficiency, PCA, and liver biotin concentrations demonstrated that fingerling C. catla require biotin in the range of 0.41–0.87 mg/kg diet.     

Dietary biotin requirement of fingerling Channa punctatus (Bloch)

ABSTRACT

Dietary biotin requirement of fingerling Channa punctatus (4.52 ± 0.46 g) was estimated by conducting a 16-week growth trial. Fish were fed casein gelatin-based purified diets (450 g/kg crude protein, 18.39 kJ/g gross energy) with seven levels of dietary biotin (0, 0.04, 0.09, 0.47, 1.02, 1.43, and 1.96 mg/kg diet) to triplicate groups near to satiation. Significantly higher absolute weight gain (P = 0.0018), specific growth rate (P = 0.0027), protein gain (P = 0.0016), protein deposition (P = 0.0038), and lower feed conversion ratio (P = 0.0003) were shown in fish fed diet containing 0.47 mg/kg biotin, whereas liver biotin concentration showed a significant improvement (P = 0.0021) with increasing levels of dietary biotin up to 1.02 mg/kg. Broken-line analysis of absolute weight gain, protein gain, and liver biotin concentrations indicated that fingerling C. punctatus require biotin at 0.46, 0.44, and 0.97 mg/kg diet. Based on protein gain, optimum pyridoxine requirement for fingerling C. punctatus is recommended at 0.44 mg/kg diet.     

Dietary vitamin E requirement for maximizing the growth,conversion efficiency,biochemical composition and haematological status of fingerling Channa punctatus

The effect of feeding graded levels of vitamin E (E₀, E₂₀, E₄₀, E₆₀, E₁₀₀, E₁₄₀, E₁₈₀, E₂₂₀, E₂₆₀) in nine casein–gelatin‐based isonitrogenous (450 g kg^?1 crude protein) and isoenergetic (17.97 kJ g^?1 gross energy) experimental diets was evaluated in fingerling Channa punctatus for 12 weeks. Growth, nutritional and haematological parameters were studied. Hepatic lipid peroxidation as thiobarbituric acid‐reactive substances (TBARS) was also assayed. The maximum absolute weight gain (AWG g/fish, 55), best feed conversion ratio (FCR, 1.32), protein retention efficiency (PRE, 40%) and energy retention efficiency (ERE, 76%) were achieved in fish fed on a diet supplemented with 140 mg vitamin E kg^?1 diet (E₁₄₀). A consistent decline in the hepatic TBARS concentration and an improvement in haematocrit (Hct) and haemoglobin (Hb) were displayed in fish fed on diets with increasing concentrations of vitamin E up to 140 mg kg^?1 (E₀–E₁₄₀), beyond which (E₁₈₀–E₂₆₀) a reverse trend in these parameters was evident. Based on the broken‐line regression and exponential analyses of AWG, FCR, PRE, ERE, Hb and Hct data, diets for fingerling C. punctatus should contain vitamin E in the range of 140–169 mg kg^?1 to maintain satisfactory fish performance.     

Effects of dietary lysolecithin on growth performance,feed utilization,intestinal morphology and metabolic responses of channel catfish (Ictalurus punctatus)

This study investigated the effects of dietary lysolecithin on growth performance, feed utilization and metabolic responses of channel catfish (Ictalurus punctatus). Fish (initial weight: 14.77 ± 0.45 g) were randomly fed one of five practical diets supplemented with graded levels of lysolecithin (0, 125, 250, 375 and 500 mg/kg) in quadruplicate groups for 10 weeks. Results showed that no significant differences in weight gain, condition factor and viscerosomatic index among all the treatments. Fish fed diet supplemented with 250 mg/kg lysolecithin had significantly decreased feed conversion ratio and significantly increased protein efficiency ratio compared to that fed the control diet. The group with 250 mg/kg of dietary lysolecithin had higher protein and lower lipid contents in the whole body, and lower lipid content in the liver than those in the control group. Groups supplemented with 250–500 mg/kg of dietary lysolecithin had significantly higher gastric and intestinal lipase activities than the control group. Dietary lysolecithin at the level of 250 mg/kg significantly increased the activities of Na⁺, K⁺‐ATPase, alkaline phosphatase, total antioxidative capacity, total superoxide dismutase, glutathione peroxidase and catalase and significantly decreased the content of malondialdehyde compared to the control diet. In conclusion, dietary supplementation of lysolecithin could confer benefits of feed utilization, body composition and antioxidative capacity of channel catfish.     

Optimization of Dietary Manganese for Rainbow Trout,Oncorhynchus mykiss,Fed a Plant‐based Diet

Juvenile rainbow trout were fed a plant‐based diet supplemented with inorganic Mn added at 0, 0.5, 1, 2, 4, 8, 16, or 32 mg/kg diet for 12 wk. Whole‐body Mn concentrations increased with increasing dietary levels. Rainbow trout fed 2–8 mg Mn/kg diet exhibited weight gain that was significantly higher than fish fed 0, 0.5, 1, 16, and 32 mg Mn/kg diet. Feed conversion ratio (FCR) showed a similar trend, where FCR values decreased with increasing dietary Mn until concentrations reached 8 mg Mn/kg, after which they increased. A rational nonlinear model (R² = 0.84) fit to weight‐gain data showed that the optimal predicted supplementation level for Mn was 4.8 mg/kg diet. The optimal predicted supplementation level for Mn was similar for FCR (5 mg Mn/kg diet). The predicted 5 mg/kg diet of supplemental Mn required for the plant‐based diet formulation examined in this study is lower than the National Research Council–recommended supplementation level of 12 mg/kg. However, due to potential differences in bioavailability or retention of Mn among plant‐protein sources, the level of dietary supplementation for optimal growth could be slightly higher or lower depending on the dietary formulation.     

Effect of dietary lipid on growth,body composition,serum biochemistry and hepatic metabolite alteration in Chinese rice field eel (Monopterus albus) fingerlings

Five isonitrogenous and isocaloric diets containing dietary lipid concentrations from 71.90 to 142.70 g/kg were formulated and fed to Chinese rice field eel Monopterus albus fingerlings (5.00 ± 0.50 g). The highest values of weight gain, specific growth rate (SGR), together with the lowest feed conversion ratio (FCR) were found in fish fed with 89.10 g/kg lipid diet. Fish fed with 71.90 g/kg diet (F1) had higher hepatosomatic index, viscerosomatic index and whole‐body crude lipid than fish in the other four treatments (p < .05). Plasma concentration of triacylglycerol and the activity of alanine aminotransferase were also higher in fish fed with F1 diet. Whole‐body fatty acid profile varied exclusively, but with a stable value of n?3/n?6 ratio. Gas chromatography–mass spectrometry‐based metabolomics identified eighteen differential metabolites (including idose, alanine, glutamic acid, serine and hypotaurine) in liver affected by dietary lipid content using PLS‐DA analysis. The subsequent pathway enrichment revealed ten affected pathways, with the top three pathways being glycine, serine and threonine metabolism; starch and sucrose metabolism; and D‐glutamine and D‐glutamate metabolism. The broken‐line model of SGR suggested that a dietary lipid concentration of 83.50 g/kg was appropriate for M. albus fingerlings.     

Dietary nucleotide‐rich yeast supplementation improves growth,innate immunity and intestinal morphology of Pacific white shrimp (Litopenaeus vannamei)

An 8‐week feeding trial was conducted to evaluate the effects of dietary nucleotide (NT)‐rich yeast supplementation on growth, innate immunity and intestinal morphology in Pacific white shrimp (Litopenaeus vannamei). Four isonitrogenous and isolipidic practical diets were formulated to contain 0 (control), 10, 30 and 50 g/kg of NT‐rich yeast, respectively. A total of 480 shrimp with an average initial body weight of 1.86 ± 0.02 g were randomly allocated into four groups, with four replicates per group and 30 shrimp each replicate. The results indicated that shrimp fed the diet containing 50 g/kg NT‐rich yeast had significantly higher weight gain (WG), specific growth rate (SGR) and protein efficiency ratio (PER) than those fed the control diet, and the lowest feed conversion ratio (FCR) was observed in the shrimp fed the 50 g/kg NT‐rich yeast supplemental diet. However, there was no significant difference in survival among all treatments. The crude protein of whole shrimp in the 50 g/kg NT‐rich yeast group was higher than that in the control group. Total protein, triglyceride concentrations, the activities of aspartate aminotransferase and alanine aminotransferase in serum were significantly influenced by the dietary NT‐rich yeast supplementation. The activities of serum phenoloxidase (PO) and lysozyme (LZM) of shrimp fed the diet containing 50 g/kg NT‐rich yeast were higher than those in shrimp fed the other diets. Relative expressions of alp and lzm significantly upregulated in the 30 g/kg NT‐rich yeast group compared to the control group. The intestinal fold height and fold width in the 30 g/kg NT‐rich yeast group were significantly higher than those fed the control diet; and the highest microvillus height occurred in the shrimp fed the 50 g/kg NT‐rich yeast diet. In summary, dietary 30–50 g/kg NT‐rich yeast supplementation promotes growth performance, enhances innate immunity and improves intestinal morphology of Litopenaeus vannamei.     

Dietary calcium requirement of red swamp crayfish (Procambarus clarkia)

To investigate dietary calcium requirement of red swamp crayfish (Procambarus clarkia), six semi‐purified diets were formulated to contain different concentrations of calcium (2.7(control group), 6.1, 11.9, 17.6, 23.5 and 29.1 g/kg calcium). Each diet was hand‐fed to triplicate of 15 crayfish with average initial body weight (6.22 ± 0.87) g for 8 weeks. The results showed that weight gain rate (WGR) significantly increased and feed conversion ratio (FCR) significantly decreased from 11.9 to 23.5 g/kg groups (p < .05). Protease activities in intestine and hepatopancreas and parathyroid hormone concentrations in serum significantly decreased with increasing dietary calcium levels (p < .05), while calcium and phosphorus contents in exoskeleton, calcium content in muscle and calcitonin concentrations in serum significantly increased (p < .05). The activities of lipase and amylase in intestine and hepatopancreas, serum alkaline phosphatase and total vitamin D concentrations in serum had significant increase as dietary calcium content increased up to 11.9–17.6 g/kg (p < .05). The inorganic phosphorus content in 29.1 g/kg group was significantly lower than those in other groups (p < .05). Broken‐line model analysis based on WGR and quadratic curve model analysis based on FCR showed that optimal dietary calcium requirement of red swamp crayfish ranged from 12.7 to 17.1 g/kg.