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.     

Effect of dietary iron levels on growth,iron concentration in tissues,and blood concentration levels of transferrin and hepcidin in bighead carp (Aristichthys nobilis)

A 60‐day feeding trial was conducted to estimate the effects of dietary iron (Fe) levels on growth, Fe concentration in the liver, spleen, and blood, and transferrin and hepcidin concentrations in the blood of bighead carp (Aristichthys nobilis). The six experimental diets were formulated to contain different Fe levels (0, 43.1, 84.2, 123.3, 162.2 and 203.1 mg/kg of dry diet) using ferrous sulphate (FeSO₄) as the source. The weight gain (WG) and the specific growth ratio (SGR) of A. nobilis fed with a dietary Fe level of 123.3 mg/kg were significantly higher than that of the 0 mg/kg Fe group (p < .05). The results indicated that the growth was affected by dietary Fe levels. Regression analysis of WG and SGR at different levels of dietary Fe suggests that the appropriate dietary requirement of Fe for the bighead carp larvae is 120–134.36 mg/kg. The Fe contents in different tissues were as follows: spleen > liver > whole body. When the Fe dietary content increases to 162.2 mg/kg, the blood concentrations of Fe significantly decreased and thereafter increased, hepcidin significantly decreased and thereafter decreased, and transferrin significantly increased and thereafter decreased. The results indicate that the transferrin blood content significantly increased with decreasing hepcidin of up to 264.63 μg/ml content and thereafter decreased. It could be concluded that after transferrin saturation, hepcidin functions to maintain iron balance in the blood of A. nobilis by decreasing transferrin content.     

Investigations on zinc bioavailability of different sources and dietary zinc requirement in juvenile grouper Epinephelus coioides

An experiment was implemented to study the effect of dietary zinc levels from three zinc sources on growth performance, immunity, and tissue mineral elements deposition on juvenile grouper. Based on the zinc free feeds, dietary zinc levels of 0, 10, 20, 40, 80, and 160 mg/kg were added from zinc sulphate (ZnSO₄), tetrabasic zinc chloride (TBZC), and 2‐hydroxy‐4‐(methylthio) butyrate zinc (Zn‐HMB). The results of the 8‐week study indicated that the weight gain rate (WGR) and specific growth rate (SGR) at level 10 mg/kg were significantly higher than the control fed and the reached a plateau until level 80 mg/kg, when the sources were ZnSO₄ and Zn‐HMB. WGR and SGR decreased significantly at level 160 mg/kg compared to 80 mg/kg in group TBZC. Feed coefficient (FCR) of all zinc source groups showed trend of decrease before rising. The alkaline phosphatase (AKP) in serum, catalase (CAT), total superoxide dismutase (SOD), copper‐zinc superoxide dismutase (Cu‐Zn SOD) in liver and zinc concentrations in whole body and vertebrae increased significantly than those in control group and then kept steadily in all treatments. Regardless of the sources, the manganic content of whole body or vertebra showed a downtrend. Based on the WGR, the dietary zinc requirements in juvenile grouper were 52.94 mg/kg from ZnSO₄. The average relative bioavailability (RBV) of TBZC and Zn‐HMB was 169.33% and 200.33%, respectively, compared to ZnSO₄.     

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.     

Effects of dietary zinc level on performance,zinc status,tissue composition and enzyme activities of juvenile Siberian sturgeon,Acipenser baerii (Brandt 1869)

This study conducted to evaluate the effect of dietary zinc (Zn) levels on feed utilization, tissue Zn composition and serum enzyme activities of juvenile Siberian sturgeon, Acipenser baerii. Five isoenergetic and isonitrogenous semi‐purified diets were formulated with increasing Zn sulphate (ZnSO₄.5H₂O) level to provide the actual Zn values of 14.7 (control), 20.8, 27.3, 37.7 and 46.4 mg/kg diet. Each diet was assigned to three groups of 20 experimental Siberian sturgeons with uniform size (initial weight of 26.52 ± 0.94 g) for a period of 8‐week feeding trial. Results showed that growth performance and muscle protein content were significantly increased with increasing dietary Zn level up to 27.3 mg/kg (p < .05), beyond which they remained significantly unchanged (p > .05). Muscle lipid content significantly declined with increasing dietary Zn level. While muscle and serum Zn contents were not significantly changed among treatments (p > .05), liver Zn content tended to rise with increasing dietary Zn supplementation. Alkaline phosphatase, superoxide dismutase and glutathione peroxidase activities were also raised with increasing dietary Zn level. The adequate amount of dietary Zn requirements for the Siberian sturgeon was estimated to be 28.24 mg/kg based on the relative growth rate and 34.60 mg/kg based on the liver Zn content.     

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.     

Synergistic effect of sodium selenite and Pediococcus acidilactici on growth,intestinal bacterial counts,selenium bioavailability,hepatic enzymes and non‐specific immune response in rainbow trout (Oncorhynchus mykiss)

Lactic acid bacteria (LAB) have a crucial role in inorganic selenium metabolism as well as their known desirable effects on fish. In this study, the synergistic effects of dietary sodium selenite and Pediococcus acidilactici on growth performance, intestinal bacterial counts, selenium bioavailability, hepatic antioxidant enzyme thioredoxin reductase activity and hepatic glycolytic enzyme activity that is hexokinase, phosphofructokinase and pyruvate kinase, and non‐specific immune response such as serum lysozyme and complements C₃, C₄ and ACH₅₀ activity in rainbow trout (Oncorhynchus mykiss) were investigated. Thus, a 3 × 3 factorial design experiment was conducted with nine purified diets including three levels of sodium selenite (0, 1 and 2 mg/kg) and three levels of P. acidilactici (0, 7 and 9 log CFU/g). After 8 weeks of feeding, weight gain and specific growth rate were increased by increasing dietary sodium selenite and P. acidilactici levels compared to control (p < .05), whereas feed conversion ratio and condition factor was decreased by increasing dietary sodium selenite and P. acidilactici amounts in comparison with control (p < .05). Survival rate was not significantly affected among the experimental treatments (p > .05). Total cultivable bacterial populations after 4 and 8 weeks of the feeding trial were not significantly different among the dietary treatments, while LAB levels were higher in P. acidilactici‐fed groups than in control and selenium‐fed groups (p < .05). Selenocysteine, methylselenocysteine and selenomethionine levels in the intestine of rainbow trout were increased by increasing the sodium selenite and P. acidilactici levels (p < .05), and selenocysteine was found the most selenium species in the trout intestine. The quantity of total selenium in the whole body, intestine, blood, liver and muscle of rainbow trout were increased by increasing the amounts of sodium selenite and P. acidilactici compared to control (p < .05). Hepatic thioredoxin reductase and hexokinase activity were increased by increasing dietary selenium and P. acidilactici levels in comparison to control (p < .05), whereas phosphofructokinase and pyruvate kinase activity in the liver of rainbow trout were not significantly different between the dietary treatments. Serum lysozyme, complements C₃, C₄ and ACH₅₀ activity were enhanced by increasing dietary selenium and P. acidilactici levels compared to control (p < .05). The most synergistic effects of dietary supplements on growth and metabolism of rainbow trout were obtained at 2 mg/kg sodium selenite and 7 log CFU/g P. acidilactici. The findings revealed the synergistic effect of dietary selenium and P. acidilactici on growth and metabolism in rainbow trout (O. mykiss).     

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 riboflavin requirement of fingerling Channa punctatus (Bloch) based on growth,conversion efficiencies,protein retention,liver riboflavin storage,RNA/DNA ratio and carcass composition

A 16‐week experiment was conducted to determine the dietary riboflavin requirement of the fingerling Channa punctatus (6.7 ± 0.85 cm; 4.75 ± 0.72 g) by a feeding casein–gelatin‐based (450 g/kg crude protein; 18.39 kJ/g gross energy) purified diet containing graded levels of riboflavin (0, 2, 4, 6, 8, 10 and 12 mg/kg diet) to triplicate groups of fish near to satiation at 09:30 and 16:30 hr. Absolute weight gain (AWG), protein efficiency ratio (PER), specific growth rate (SGR, % per day), protein retention efficiency (PRE%) and RNA/DNA ratio were positively affected by increasing concentrations of dietary riboflavin to 6 mg riboflavin per kg diet. Feed conversion ratio (FCR) decreased up to 6 mg riboflavin per kg diet but did not decrease further with higher riboflavin supplementation. Hepatic thiobarbituric acid‐reactive substance (TBARS) concentration also supported the pattern of FCR, whereas superoxide dismutase and catalase activities increased with increasing concentrations of dietary riboflavin from 0 to 6 mg/kg. Liver riboflavin concentrations increased with increasing levels of riboflavin up to 8 mg/kg diet. Broken‐line regression analysis of AWG, PRE and liver riboflavin concentrations of fingerling C. punctatus with dietary riboflavin level indicated optimum growth and liver riboflavin saturation at 5.7, 6.1 and 7.7 mg riboflavin per kg diet, respectively.     

The dietary zinc requirement of a benthic fish Paramisgurnus dabryanus

This study was conducted to assess the dietary zinc (Zn) on growth and antioxidant capacity of adult Paramisgurnus dabryanus. Zinc methionine (ZnM) of grade levels (0, 20, 40, 80, 120 and 160 mg/kg diet respectively) was supplemented, providing actual dietary Zn concentrations of 24.38, 28.03, 31.68, 38.98, 46.28 and 53.58 mg/kg diet respectively. P. dabryanus with an initial body weight of 5.21 ± 0.15 g were fed these Zn supplemented diets for 8 weeks. Results showed that the weight gain (WG) and specific growth rate (SGR) increased with increasing dietary Zn levels from 24.38 to 31.68 mg/kg, and then decreased above these levels. The hepatopancreas index (HIS) was the highest at 31.68 mg/kg, followed by 38.98 mg/kg. The enzymatic antioxidants in plasma and hepatopancreas firstly increased, and reached the peak at 31.68 or 38.98 mg/kg, then kept stable with the increase of dietary Zn levels. On the contrary, the content of MDA firstly decreased, and then increased. According to WG and T‐AOC in plasma, the Zn requirement was determined to be 32.02 and 32.24 mg/kg, respectively, based on regression analysis. The relatively low dietary Zn requirement of P. dabryanus may involve in the evolutional adaption of metal absorption and utilization to their habitat.     

Effects of γ‐aminobutyric acid supplementation on the growth performance,serum biochemical indices and antioxidant status of pharaoh cuttlefish,Sepia pharaonis

This study evaluated the effects of dietary γ‐aminobutyric acid (GABA) on the growth performance, serum biochemical indices and antioxidant status of pharaoh cuttlefish, Sepia pharaonis. Cuttlefish were cultured in open‐culturing cement pool systems for 8 weeks. Six practical diets supplemented with graded levels of GABA (0, 20, 40, 60, 80 and 100 mg/kg) were formulated. Each diet was randomly assigned to triplicate groups of 60 cuttlefish (mean weight: 10.33 g), the cuttlefish were fed two times per day to apparent satiation. The results showed that the specific growth rate (SGR), weight gain (WG) and feed efficiency (FE) significantly increased with dietary GABA supplementation (p < .05). The survival rate (SR) and protein content in muscle significantly increased when 58.9 mg/kg GABA supplied. Moreover, the nitric oxide (NO) content and acid phosphatase (ACP) activity in serum were significantly increased with dietary GABA supplementation (p < .05), while the activity of aspartate aminotransferase (AST) in serum decreased significantly when supplied with GABA at 58.9 mg/kg (p < .05). In addition, dietary GABA improved antioxidation activity by significantly increasing the activities of superoxide dismutase (SOD) and catalase (CAT) but decreasing malondialdehyde (MDA) levels in the liver and gill (p < .05). On the basis of the quadratic regression analysis of FE, the optimum content of dietary GABA in S. pharaonis was estimated to be 55.3 mg/kg. The findings of this study demonstrated that dietary GABA had a positive effect on the growth performance, serum biochemical indices and antioxidant status of S. pharaonis.     

Effects of organic selenium supplemented diet on growth performance and antioxidant response in Cirrhinus mrigala

The present study was conducted to evaluate the …effect of dietary selenium on growth performance and antioxidant enzymes activity in Cirrhinus mrigala for a period of 45 days. Four numbers of experimental diets were prepared, T_c for Control (0 mg organic selenium/kg of diet), T₁ (2.5 mg organic selenium/kg of diet), T₂ (5.0 mg organic selenium/kg of diet) and T₃ (10 mg organic selenium/kg of diet). The water quality parameters (temperature, DO, pH, conductivity, hardness, ammonia, nitrate and nitrite) were found to be insignificant (p > .05) among all the treatments. Superoxidase dismutase (SOD) was found to be significantly highest in T₂ (6.10 ± 0.07) when compared with the other treatments. Similarly, catalase (CAT) activity in T₁ (13.21 ± 0.13) was significantly (p < .05) different with that of Control, T₂ and T₃. Present study also revealed that 2.5mg organic selenium/kg supplemented diet (T₁) showed highest results in net weight gain (15.55 ± 1.36 g), net weight gain percentage (185.88 ± 8.98%) and SGR (2.35 ± 0.06 g) compared with other experimental diet.     

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

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

High dietary starch inclusion impairs growth and antioxidant status,and alters liver organization and intestinal microbiota in largemouth bass Micropterus salmoides

Five diets (D1, D2, D3, D4 and D5) containing 0, 50, 100, 150 and 200 g starch per kg diet were formulated to investigate the effects of starch level on largemouth bass, Micropterus salmoides. Fish (initial weight: 22.00 ± 0.02 g) were fed the five diets for 90 days. Results indicated that weight gain, specific growth rate and survival of fish fed higher dietary starch level (200 g/kg) were lower than those of fish fed the lower dietary starch levels (0–50 g/kg). Higher dietary starch levels (150–200 g/kg) have a negative effect on antioxidant ability (total superoxide dismutase: T‐SOD; malonyldialdehyde: MDA; total antioxidant capacity: T‐AOC; glutathione peroxidase: GSH‐Px) and liver health (cellular contents leaked, nucleus deformed, endoplasmic reticulum and golgi body disappeared) of largemouth bass. Lower dietary starch levels (0–50 g/kg) modified intestinal microbiota of largemouth bass represented by increasing the relative abundance of beneficial bacterial such as Bacilli, Lactobacillales and Bacteroidales. These results indicated that dietary starch level above 50 g/kg had a negative effect on growth performance and antioxidant status of largemouth bass. Moreover, high dietary starch levels are potentially associated with negative alterations in liver structure and function, and decrease of beneficial gut microbes.     

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.     

Dietary choline requirement of juvenile olive flounder (Paralichthys olivaceus)

An eight‐week study was conducted to determine the optimum dietary choline level in juvenile olive flounder, Paralichthys olivaceus. Seven diets were prepared to contain 0, 250, 500, 750, 1,000, 2,000 and 3,000 mg/kg diet. Juveniles (5.9 ± 0.03 g; 5.5 ± 0.4 cm; mean ± SD) were randomly distributed into 21 tanks (25 fish/tank) and fed one of the diets in triplicates. Survival rate of fish fed the diet containing the lowest choline level was significantly lower than those of fish fed the other diets (p < 0.05). Final body weight, weight gain, specific growth rate, feed efficiency and protein efficiency ratio significantly increased with increasing choline levels up to 1,000 mg/kg diet. Whole‐body protein and lipid contents increased in accordance with choline levels up to 750 mg/kg diet, beyond which they plateaued. Liver and muscle lipid contents elevated with increasing choline levels up to 2,000 mg/kg diet. Plasma cholesterol esters, triglycerides, cholesterol and total lipids were significantly influenced by the graded choline levels; however, responses of those indices were not identical. Broken‐line analyses of weight gain and liver choline concentrations responding to the graded choline levels revealed that choline requirements of the juvenile flounder could be between 847 and 1,047 mg/kg diet.     

Effect of dietary iron (Fe) levels on growth performance,hepatic lipid metabolism and antioxidant responses in juvenile yellow catfish Pelteobagrus fulvidraco

This study was conducted to determine effects of dietary Fe levels on growth performance, hepatic lipid metabolism and antioxidant response for juvenile yellow catfish Pelteobagrus fulvidraco. Yellow catfish were fed six isonitrogenous and isolipidic diets containing Fe levels of 16.20, 34.80, 54.50, 76.44, 100.42 and 118.25 mg/kg for 8 weeks. Weight gain (WG) and specific growth rate (SGR) increased with dietary Fe levels from 16.20 to 54.50 mg/kg diet and then plateaued over the level. Feed conversion rate (FCR) was highest and protein efficiency rate (PER) was lowest for fish fed the lowest Fe levels of diet. Fe contents in whole body and liver increased with increasing dietary Fe levels. Hepatic lipid content was lowest, but mRNA levels of carnitine palmitoyltransferase (CPT‐1) and peroxisome proliferator‐activated receptor α (PPARα) were highest for fish fed 54.50 mg Fe/kg diet. Fish fed adequate dietary Fe levels reduced hepatic malondialdehyde (MDA) level and increased activities of antioxidant enzymes Superoxide dismutase (SOD), Catalase (CAT) and GS. Based on the broken‐line regression analysis of WG against dietary Fe levels, optimal dietary Fe requirement for yellow catfish was 55.73 mg Fe/kg diets. Fe‐induced changes in MDA levels and antioxidant enzymatic activities paralleled with the change in hepatic lipid content, suggesting the potential relationship between oxidative stress and hepatic lipid accumulation in yellow catfish.     

Dietary lysine requirement of juvenile Pseudobagrus ussuriensis

An 8‐week feeding trial was conducted to determine dietary lysine requirement of juvenile Pseudobagrus ussuriensis (initial body weight: 0.60 g). Six isonitrogenous (crude protein, 400 g/kg) and isolipidic (crude lipid, 50 g/kg) diets were formulated to contain graded levels of dietary lysine (12.8, 19.9, 26.5, 34.0, 40.8 and 44.1 g/kg dry diets, respectively). The results indicated that weight gain, specific growth rate, productive protein value and protein efficiency ratio increased, while feed conversion ratio decreased with increasing dietary lysine level up to 34.0 g/kg dry diet and then levelled off. Fish fed diet with 12.8 g/kg lysine had the lowest lysine content (58.6 g/kg dry matter) in muscle, while fish fed diet with 34.0 g/kg lysine had the highest value (61.6 g/kg dry matter; p < .05). Broken‐line analysis on the basis of weight gain showed that the optimal dietary lysine requirement for maximum growth of juvenile Pseudobagras ussuriensis is 33.5 g/kg dry diet (82.4 g/kg dietary protein). Quadratic regression analysis of protein efficiency ratio against dietary lysine levels indicated that the optimal dietary lysine requirement of juvenile Pseudobagras ussuriensis is 36.4 g/kg dry diet (89.5 g/kg dietary protein).     

Effects of dietary astaxanthin on growth,blood biochemistry,antioxidant, immune and inflammatory response in lipopolysaccharide‐challenged Channa argus

The present study investigated the effects of dietary astaxanthin on the growth, blood biochemical, antioxidant, immune and inflammatory response in lipopolysaccharide‐challenged Channa argus. A total of 0, 50, 100 and 200 mg/kg of astaxanthin were added to the basal die for 56 days. After the feeding experiment, each group was subjected to a lipopolysaccharide challenge (except for the Control group). The results showed that adding astaxanthin to the diet can significantly increase the weight gain and specific growth rate and decrease the feed conversion ratio of C. argus; the highest weight gain, specific growth rate and minimum feed conversion ratio occurred in the 100 mg/kg group. Furthermore, dietary astaxanthin supplementation can alleviate the negative effects of lipopolysaccharides by increasing the levels of alkaline phosphatase, lysozyme, complement 3, complement 4, total serum protein, albumin, globulin, superoxide dismutase, catalase and glutathione peroxidase and decrease the serum cortisol, aspartate aminotransferase, alanine aminotransferase, glutathione peroxidase, and malondialdehyde. Dietary astaxanthin supplementation also can decrease the relative expression of inflammatory genes (nuclear factor κB, interleukin‐1, interleukin‐8 and tumour necrosis factor‐α) in the liver, spleen, kidney and intestine. To summarise, dietary astaxanthin addition can improve the growth performance and attenuate the negative effects of lipopolysaccharide challenge in C. argus. The optimal amount of astaxanthin is 100 mg/kg.