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.     

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.     

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.     

Effects of dietary n‐3HUFA on different growth stages of the white shrimp,Litopenaeus vannamei: Growth,haematological characteristics,enzyme activities and fatty acid profiles

This study investigated the effects of n‐3 high unsaturated fatty acid (n‐3HUFA) levels on the growth performance, antioxidant enzyme activities and fatty acid profiles of both subadult and adult Litopenaeus vannamei (L. vannamei). Seven iso‐nitrogenous and iso‐lipidic diets were used, containing n‐3HUFA concentrations of 1.6 (control), 4.8, 7.4, 13.9, 23.9, 29.2 and 34.4 g/kg, respectively. Two 8‐week feeding trials were conducted to determine the dietary n‐3HUFA requirements of L. vannamei with an initial body weight of 4.25 ± 0.00 g (subadults) and 8.50 ± 0.01 g (adults). The results showed that the dietary n‐3HUFA level significantly affected the weight gain rate (WGR), specific growth rate, the feed conversion ratio and the hepatosomatic index (HSI) (p < 0.05), but did not significantly affect the survival rate (p > 0.05). At appropriate level, dietary n‐3HUFA improved growth performance and HSI of both subadult and adult L. vannamei. Both subadults and adults showed significant differences in body composition (p < 0.05), except for moisture and crude ash (p > 0.05). Cholesterol and low‐density lipoprotein significantly decreased with increasing dietary n‐3HUFA both in subadults and adults (p < 0.05); however, triglyceride showed no significant change (p > 0.05). High‐density lipoprotein (HDL) in subadults was significantly affected by dietary n‐3HUFA (p < 0.05), but followed no apparent regularity; HDL significantly changed in adults and showed an upward trend followed by a downward trend (p < 0.05). There was no significant effect on aspartate transaminase (AST) activity in subadults, but AST in adults and alanine transaminase (ALT) in subadults and adults were significantly affected (p < 0.05). Dietary n‐3HUFA significantly affected serum polyphend oxidase, malic dehydrogenase, alkaline phosphatase, superoxide dismutase and sodium‐potassium adenosine triphosphatase enzyme activities in gills (p < 0.05). The fatty acid composition of the shrimp tissue was associated with the fatty acid composition of the diet. Dietary n‐3HUFA supplementation significantly improved the contents of tissue ∑HUFA and n‐3HUFA, increased the n‐3/n‐6 ratio in the tail muscle and decreased the contents of tissue polyunsaturated fatty acid and saturated fatty acid (p < 0.05). Based on the WGR, the broken‐line equations indicated that the optimum requirements of dietary n‐3HUFA were determined to be 9.0 and 5.1 g/kg for subadult and adult L. vannamei, respectively.     

Effect of dietary sodium butyrate on growth performance,enzyme activities and intestinal proliferation‐related gene expression of juvenile golden pompano Trachinotus ovatus

The present study was conducted to investigate the effects of dietary sodium butyrate on growth performance, intestine enzyme activities and intestinal proliferation‐related gene expression of juvenile golden pompano Trachinotus ovatus. A basal diet was supplemented with sodium butyrate at 0.0 (control), 0.25, 0.5, 1, 2 and 4 g/kg feed for 8 weeks. The final body weight, weight gain (WG), specific growth rate (SGR) and condition factor (CF) increased with increasing dietary sodium butyrate up to 2.0 g/kg, and thereafter declined, while feed conversion ratio exhibited an opposite trend. Compared with the control, the 2.0 g/kg sodium butyrate group had higher condition factor (CF) significantly (p < 0.05). Whole body ash decreased with increasing dietary sodium butyrate level, with the lowest whole body ash content in 4.0 g/kg sodium butyrate (p < 0.05). Compared with the control, the 2.0 g/kg sodium butyrate group had significantly increased plasma glucose, cholesterol, albumin level, A/G ratio, ALT and AST contents (p < 0.05), while significantly decreased plasma ALT/AST ratio (p < 0.05). As for the intestinal digestive and brush border enzymes activities, compared with the control, the 2.0 and 4.0 g/kg sodium butyrate groups had significantly increased intestinal protease, amylase, AKP and Na⁺‐K⁺‐ATPase activities (p < 0.05), respectively. The relative level of intestinal CDX2 mRNA of fish significantly increased with dietary sodium butyrate level. Compared with the control, the 2.0 g/kg sodium butyrate groups had significantly increased the expression of intestinal CDX2 and CREB mRNA (p < 0.05), respectively. In conclusion, these results suggested that the optimum sodium butyrate level for juvenile golden pompano could be 2.0 g/kg of the diet.     

Effect of dietary vitamin B6 supplementation on growth and intestinal microflora of juvenile golden pompano (Trachinotus ovatus)

In order to investigate the dietary vitamin B₆ (VB₆) requirement for juvenile golden pompano, an experiment of six different diets with six dietary VB₆ levels (0, 3.75, 7.47, 10.6, 13.7 and 18.5 mg/kg) was conducted. The results indicated that the content of dietary VB₆ significantly increased weight gain rate (WGR), specific growth rate (SGR) and feed conversion ratio (FCR; p < 0.05). Golden pompano fed diet containing 7.47 mg/kg VB₆ achieved the maximum ALT, AST, GPx, hepatic VB₆ concentrations as well as the minimum MDA, however, the ALT, AST, GPx and hepatic VB₆ concentrations decreased while MDA increased with a further increase in dieatry VB₆. The highest values of GR and POD occurred at the 10.6 and 13.7 mg/kg dietary VB₆ (p < 0.05) respectively. A diet supplemented with 7.47 mg/kg VB₆ increased intestinal Na⁺, K⁺‐ATPase, Chymotrypsin, γ‐glutamyl transpeptidase, creatine kinase and amylase activities (p < 0.05). The relative abundance of Tenericutes and Bacteroidetes decreased while Proteobacteria and Firmicutes improved with an increase in dietary VB₆ levels up to 7.47 mg/kg. Quadratic regression analysis on WGR, hepatic VB₆ concentrations, AST and ALT indicated that the optimum dietary VB₆ levels for juvenile golden pompano were 8.84–9.28 mg/kg.     

Effect of dietary Clostridium butyricum and different feeding patterns on growth performance,antioxidant and immune capacity in freshwater prawn (Macrobrachium rosenbergii)

An 8‐week study was conducted to evaluate the effects of different feeding patterns with dietary Clostridium butyricum supplementation on growth performance, antioxidant and non‐specific immune responses in freshwater prawn, Macrobrachium rosenbergii (0.39 ± 0.001 g). There were four feeding methodologies: feeding basal diet continuously (P1); feeding diet with 500 mg/kg C. butyricum continuously (P2); feeding diet with 500 mg/kg C. butyricum 5 days after 2 days of basal diet (P3) and feeding diet with 500 mg/kg C. butyricum 2 days after 5 days of basal diet (P4). The results revealed that prawns in P3 had the highest weight gain rate (WGR) and lowest feed conversion ratio (FCR) than the other groups. Haemolymph total protein levels and superoxide dismutase activity increased significantly in P2, P3 and P4 groups, while malondialdehyde content and anti‐superoxide anion levels decreased significantly compared to control. The mRNA expression of intestinal dorsal and Toll in P2 and P3 groups decreased significantly compared to control. Prawns in P3 exhibited improved growth performance, increased antioxidant capacity and enhanced immune function. We concluded that feeding diet with 500 mg/kg C. butyricum for 5 days after 2 days of basal diet was recommended for M. rosenbergii.     

Dietary potassium requirement of fingerling Indian major carp,Labeo rohita (Hamilton), based on growth parameters,gill Na+‐K+ ATPase activity,tissue mineralization and antioxidant activities

To quantify the dietary potassium requirement of fingerling Labeo rohita (6.2 ± 0.12 cm; 1.98 ± 0.06 g), seven purified experimental diets (350 g/kg crude protein and 16.72 kJ/g gross energy) with graded levels of potassium (0.32, 1.35, 2.41, 3.46, 6.48, 9.47 and 12.39 g/kg diet) were fed to triplicate groups of fishes at 08:00, 12:00 and 16:00 hr to apparent satiation for 8 weeks. Live weight gain (LWG; 671.46%), specific growth rate (3.65%/day), protein efficiency ratio (2.16), protein gain (PG; 2.41 g/fish) and feed conversion ratio (1.32) were found to be best in fish fed diet containing 3.46 g/kg potassium. Gill Na⁺‐K⁺ ATPase activity was also highest in fish fed diet with 3.46 g/kg potassium. Potassium content of whole‐body, vertebrae and scales increased significantly with the increase in dietary potassium level up to 6.48 g/kg. Significant changes were also noted in serum malondialdehyde content, superoxide dismutase, catalase, glutathione peroxidase and alkaline phosphatase activity. Based on the maximum live weight and protein gain observed in the present study, the inclusion of 3.55 g/kg potassium is recommended for developing potassium‐balanced commercial feeds for intensive culture of fingerling L. rohita.     

Improvement of growth performance,digestive enzymes and body composition of Persian sturgeon (Acipenser persicus) following feeding on probiotics: Bacillus licheniformis,Bacillus subtilis and Saccharomyces cerevisiae

The individual and combinational effects of probiotics on Persian sturgeon (Acipenser persicus) were evaluated through assessing the growth performance, proximate body composition, digestive enzymes and intestinal morphology. On the basis of feeding with experimental diets, the fish were assigned into four groups denoted as follows: control (basal diet), D‐Pro (basal diet + Bacillus subtilis and Bacillus licheniformis), D‐Pro/Yeast (basal diet + B. subtilis and B. licheniformis + Saccharomyces cerevisiae), Yeast (basal diet + S. cerevisiae). Maximum mean weight and length were measured for the fish fed with D‐pro regime. weight gain (WG), body weight gain (BWI%),  feed efficiency (FE%), protein efficiency rate (PER), lipid efficiency rate (LER), and condition factor (CF) demonstrated the highest values for the fish fed with the diets containing D‐Pro and/or D‐Pro/yeast. LER and food conversion ratio (FCR) showed the highest performance for the fish received the D‐Pro diet. The diets containing D‐Pro exhibited higher performance in enhancing the activity of protease and lipase than the one supplemented only with the yeast, whereas the regimes treated with the yeast exhibited higher amylase activity. The fish received D‐Pro exhibited the highest protein and fat contents, yet did the lowest contents of moisture and total ash. Taken together, the findings revealed that the dietary administration of the D‐Pro and D‐Pro/Yeast could improve the growth performance of A. persicus.     

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.     

Effects of exogenous multienzyme complex supplementation in diets on growth performance,digestive enzyme activity and non‐specific immunity of the Japanese seabass,Lateolabrax japonicus

This experiment aimed to investigate the effects of exogenous multienzyme complex (EC) on growth performance, digestive enzyme activity and non‐specific immunity of the Japanese seabass, Lateolabrax japonicus (initial weight 27.09 ± 0.08 g). EC includes protease, xylanase, glucanase and mannase. Japanese seabass were given six levels of EC (0, 0.5, 1.0, 1.5, 2.0 and 2.5 g/kg) for 28 days. Results show that EC significantly enhanced the weight gain rate and specific growth rate (p < .05), while the feed conversion ratio reduced significantly (p < .05). Activities of lipase and trypsin in liver and intestine significantly increased (p < .05). Alkaline phosphatase, superoxide dismutase and lysozyme activities in serum and liver significantly increased (p < .05), while the content of malondialdehyde in liver significantly declined (p < .05). Regression analysis showed that the optimal supplementation of EC in WGR, SGR, FCR, SOD and LZM activity in serum was 1.66, 1.67, 1.81, 1.71 and 1.53 g/kg, respectively, while the best SOD, LZM activity in liver, trypsin activity in liver and intestine supplement were 1.64, 1.51, 1.81 and 1.97 g/kg. In conclusion, EC supplemented can improve the growth performance, digestive enzyme activity and non‐specific immunity of Japanese seabass, and it is recommended that the optimal supplementation of EC in diets of Japanese seabass is 1.5–2.0 g/kg.     

Dietary lysine requirement of juvenile Protonibea diacanthus

An 8‐week experiment was conducted to determine the optimal dietary lysine requirement for juvenile Protonibea diacanthus. Six isonitrogenous and isolipidic diets were formulated to contain levels of 10.8 (L10.8), 18.2 (L18.2), 26.1 (L26.1), 33.9 (L33.9), 40.7 (L40.7) and 48.6 g/kg (L48.6) of diets and were fed to the juvenile Protonibea diacanthus, respectively. The results indicated that weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and final weight (FW) increased as the dietary lysine level increased from 10.8 to 26.1 g/kg and then decreased as the dietary lysine levels further increased (p < .05). The lowest feed conversion ratio (FCR) was found when dietary lysine level was 26.1 g/kg. Analysis of specific growth rate by two slope broken‐line model indicated that the estimated optimal dietary levels of lysine for juvenile Protonibea diacanthus was 23.06 g/kg (51.24 g/kg dietary protein).     

Effects of dietary starch levels on the growth,plasma metabolites and expression of genes involved in glucose transport and metabolism in Pelodiscus sinensis juveniles

A 10‐week feeding trial was conducted to evaluate the growth performance, glucose transport and metabolism of Chinese soft‐shelled turtles (Pelodiscus sinensis) exposure to graded levels of dietary starch (0.52%, 7.43%, 14.74%, 22.99% and 31.38%). The 360 turtles (initial body weight, 12.94 ± 0.50 g) with 12 replicates were randomly assigned to five experimental diets. The highest weight gain and specific growth rate (SGR) were observed in 7.43% group and the lowest in 31.38% group. The protein efficiency ratio, whole‐body lipid contents, hepatic glycogen contents and the 4‐hr postprandial plasma glucose levels were significantly increased with the increment of starch levels (p < .05). In contrast, the daily feed intake and feed conversion ration were significantly declined (p < .05). The mRNA levels of glucose transporter 2, glucokinase, pyruvate kinase, malic enzyme and acetyl‐CoA carboxylase alpha genes in the liver significantly increased as the increase in starch levels at 4‐hr and 24‐hr post feeding (p < .05). No significant differences were observed in the expression of gluconeogenesis genes at each time point (p > .05). These results suggested that dietary addition of starch up‐regulated hepatic glycolysis, glycogenesis and lipogenesis genes expression, but the deficient response of gluconeogenesis to dietary starch might be part of the causes limited the starch utilization. Based on the secondary polynomial regression of SGR, y = ?0.0011x² + 0.028x + 1.63 (R² = 0.9292), the 12.73% inclusion level of dietary starch was recommended in juvenile turtles.     

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.     

Effect of the dietary phosphatidylcholine at different growth stages of Pacific white shrimps,Litopenaeus vannamei

This study investigated the effects of dietary phosphatidylcholine (PC) at different growth stages of Litopenaeus vannamei (L. vannamei) with an initial weight of 0.70 ± 0.00 g (juvenile) and 4.25 ± 0.00 g (subadult) for 8 weeks. Six isonitrogenous and isoenergetic diets containing PC (0, 1.7, 5.1, 6.8, 10.2 and 13.6 g/kg) were confected using formulated with redfish meal, dehulled soybean meal and peanut meal as protein source, fish oil and corn oil as fat source. The juveniles were reared in 0.3 m³ aquarium at the density of 40 in triplicates, as well as the subadults in 0.5 m³ at the density of 40 in triplicates. Results showed PC level had significant effects on weight gain rate (WGR), specific growth rate, feed conversion ratio in juvenile and subadult shrimps and hepatosomatic index in juvenile shrimps (p < 0.05). No significant differences were found in moisture, whole body protein and crude ash (p > 0.05). Crude fat of juveniles had no significant change (p > 0.05), but subadults increased significantly (p < 0.05). Both juveniles and subadults showed that triglyceride and low‐density lipoprotein presented a downward trend with PC elevating, but high‐density lipoprotein increased gradually. Cholesterol in juveniles presented upward, but downward in subadults (p < 0.05). Dietary PC also significantly reduced the aspartate transaminase in juveniles and alanine transaminase in subadults (p < 0.05). PC supplementation significantly improved the glutathione S‐transferase activity and reduced the content of malondialdehyde in the hepatopancreas (p < 0.05). PC supplementation significantly improved gill filament sodium‐potassium adenosine triphosphatase enzyme of juvenile shrimps (p < 0.05), but subadult shrimps were not influenced (p > 0.05). PC supplementation significantly elevated the content of hepatopancreas eicosapentaenoic acid, highly unsaturated fatty acid (HUFA) and n‐3HUFA (p < 0.05), but the content of linoleic acid significantly reduced (p < 0.05). The broken‐line and quadratic regression model based on WGR showed the optimum dietary PC requirement was 10.3 g/kg and 6.5 g/kg for juveniles and subadults, respectively.     

Dietary available phosphorus requirement of crucian carp,Carassius auratus

This study was carried out to evaluate the dietary available phosphorus (AP) requirement for crucian carp (Carassius auratus). Triplicate groups were fed diets containing five graded levels of AP in 15 recirculating tanks. After a 9‐week feeding experiment, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and whole‐body and vertebrae P contents were significantly increased as dietary AP increased from 1.1 to 7.6 g/kg (p < .05) and then levelled off. N and P retention was also significantly increased as dietary AP increased to 5.5 g/kg (p < .05). Condition factor, viscerosomatic index, hepatosomatic index, whole‐body moisture, muscle P content and plasma total cholesterol were not affected by dietary P levels (p > .05). Protein and ash contents of the whole body increased linearly as the dietary P level increased, but the lipid content, plasma alkaline phosphatase activities and triacylglycerol contents showed an inverse relationship. Based on WG, FE, whole‐body P content and vertebrae P content, the optimum requirement of dietary AP for crucian carp was estimated to be 8.3, 8.3, 8.0 and 7.8 g/Kg, respectively.     

Dietary manganese requirement of juvenile hybrid grouper,Epinephelus lanceolatus × E. fuscoguttatus

An 8‐week feeding trial was conducted to estimate the optimum dietary manganese (Mn) requirement for juvenile hybrid grouper, Epinephelus lanceolatus × E. fuscoguttatus. The basal diet was formulated to contain 520 g/kg crude protein from casein and fishmeal. Manganese methionine was added to the basal diet at 0 (control group), 2.5, 5, 10, 20 and 40 mg Mn/kg diet providing 7.48, 10.34, 13.76, 19.72, 31.00 and 53.91 mg Mn/kg diet, respectively. Each diet was randomly fed to triplicate groups of juveniles, and each tank was stocked with 20 fish (initial weight, 60.06 ± 0.68 g). The manganese content in rearing water was monitored and kept below 0.01 mg/L. Results showed that the weight gain ratio (WGR), protein efficiency ratio (PER), specific growth rate (SGR), Mn contents in whole body, liver and vertebra, and activities of hepatic Mn superoxide dismutase (Mn‐SOD), total SOD (T‐SOD) and glutathione peroxidase (GSH‐PX) were significantly improved by dietary Mn supplementation (p < .05). However, dietary Mn did not affect arginase (DArg) activity. The highest feed conversion ratio (FCR) was observed in fish fed the basal diet (p < .05). No significant differences were found on the Cu and Zn contents in whole body by supplementing dietary Mn. Supplemented Mn in diets had significantly effect on liver and vertebral trace element deposition (p < .05). Fish fed the basal diet had the highest Fe and Zn contents in vertebra (p < .05). There were no significant differences on hepatic pyruvate decarboxylase (PDC) activity with supplemented Mn levels below 13.76 mg/kg. As biomarker of oxidative stress, malondialdehyde (MDA) content in liver was significantly higher in fish fed the basal diet (p < .05). Using the broken‐line models based on SGR, dietary Mn requirement of the juvenile hybrid grouper was estimated to be 12.70 mg/kg diet.     

Evaluation of dried fermented biomass as a feed ingredient in plant‐based practical diets for juvenile Pacific white shrimp Litopenaeus vannamei

Two growth trials were designed to evaluate the utilization of dried fermented biomass (DFB) in commercial type feed formulation for Pacific white shrimp, Litopenaeus vannamei. In trial 1, four experimental diets were formulated to utilize increasing levels (0, 25, 50 and 100 g/kg) of spray‐dried fermented biomass (SDFB) as a replacement of fish meal (FM). Results indicated that SDFB can be utilized up to 50 g/kg as a substitution for FM without causing growth depression in shrimp. However, dietary SDFB supplementation at 100 g/kg significantly reduced the weight gain (WG) of shrimp and increased feed conversion ratio (FCR). This reduction in performance is likely due to palatability or nutrient imbalances of the feed. In trial 2, nine experimental diets were formulated with increasing levels (0, 20, 40, 60 and 120 g/kg) of spray‐dried (S) or granular (G) DFB to replace soy protein concentrate (SPC) or SPC + corn protein concentrate (CPC). This allowed the comparison between spray‐dried and ring‐dried products. Ring drying produced a granular product, reducing dust and increasing product particle size. Shrimp fed with diet containing 20 g/kg GDFB performed the best in terms of final mean weight, WG and FCR. Significantly reduced growth and increased FCR were observed in shrimp fed diets containing 60 and 120 g/kg SDFB. Lipid content of whole body was significantly reduced when GDFB was incorporated at 120 g/kg. No significant differences were detected in survival, protein retention efficiency as well as protein and ash contents of the whole shrimp. Results from analysis of covariance indicated that the processing method (covariant) had a significant effect on final mean weight, WG and FCR. In general, shrimp fed with diet containing granular product performed better as compared to those fed with diets utilizing spray‐dried product. GDFB can be utilized in the diets up to 120 g/kg in practical shrimp feeds as a substitute for SPC and CPC without compromising the growth of shrimp. However, a significant reduction in WG was observed in the diets containing 60 and 120 g/kg SDFB. The results in the current study demonstrate that processing changes to produce a granular product produced an improved feed ingredient for shrimp.     

Reduced fishmeal allowance with constant protein input for juvenile channel catfish Ictalurus punctatus

In this study, we evaluated different dietary fishmeal and protein levels on growth performance, intestinal structure and intestinal microbial community of juvenile channel catfish, Ictalurus punctatus. A total of 1800 fish distributed into 36 tanks were fed with nine different diets containing three protein levels (300, 330 and 360 g/kg) with three fishmeal (FM) levels (0, 30 and 60 g/kg) for 90 days. The results showed that significant interactions between the protein level and FM level were observed in final weight (FW), weight gain (WG), Na⁺, K⁺‐ATPase and alkaline phosphatase (AKP) activities. The significant lowest FW, WG, Na⁺, K⁺‐ATPase and AKP activities were observed in fish fed with no fishmeal and 300 g/kg protein dietary while the highest were shown in 60 g/kg fishmeal and 330 g/kg protein treatment. Additionally, the microvillar length of the mid‐intestine in catfish was significantly affected by the interaction between dietary protein level and fishmeal level. The intestinal samples were dominated by three major phyla, Firmicutes, Proteobacteria and Fusobacteria. Genera Romboutsia and Turicibacter accounted for probably 800 g/kg of the phylum Firmicutes; meanwhile, genus Cetobacterium represented more than 900 g/kg of the phylum Fusobacteria. In conclusion, this study indicated that channel catfish juveniles can be fed with a practical diet without fishmeal as long as the protein level increased to 360 g/kg; however, if the percentage of dietary protein was 300 g/kg, it seemed that fishmeal need to be supplied as a protein source.     

Response of juvenile tench (Tinca tinca L.) fed practical diets with different protein contents and substitution levels of fish meal by soybean meal

A basal practical diet for juvenile tench (Tinca tinca) was formulated and elaborated to test several protein contents and substitution possibilities of fish meal (FM) by soybean meal (SBM) in a 90‐day trial with 5‐month‐old juveniles (30.54 mm TL, 0.30 g W). A factorial design included nine feeding treatments: three protein contents (50%, 40% or 30%) and three levels of replacement (0%, 25% or 45%) of FM protein by SBM protein. In addition, a commercial carp feed was used as reference. Final survival ranged from 98.2% to 99.4%. The 50% dietary protein with 0% or 25% replacement and 40% dietary protein with 25% replacement diets enabled higher growth (P < 0.05) and lower FCR (P < 0.05) than the rest of practical diets. Fish fed 50% dietary protein had similar growth than those fed carp feed (63.8% protein). Deformed fish averaged 1% for the practical diets and 87.6% for the carp feed. The basal practical diet has showed to be feasible and levels of 40–50% dietary protein with 25% replacement of FM protein by SBM protein can be recommended for juvenile tench aged 5–8 months.