Nutriphysiological and cytological responses of juvenile channel catfish (Ictalurus punctatus) to dietary oxidized fish oil

An 86‐day growth trial was conducted to investigate the effect of dietary oxidized fish oil on the growth and cytopathology of juvenile channel catfish (Ictalurus punctatus). Four diets containing 0 g kg^?1 (control: fresh fish oil), 30 g kg^?1 (low‐oxidized oil group), 60 g kg^?1 (medium‐oxidized oil group) and 90 g kg^?1 (high‐oxidized oil group) graded oxidized oil levels with the same dietary lipid level (90 g kg^?1 diet) were evaluated. The results show that the specific growth rate decreased with increasing dietary oxidized oil level (P < 0.05). All examined liver and kidney tissues in all dose groups exhibited what appeared as dose‐dependent cellular modifications. In addition, lipid droplet accumulation in the hepatocytes of fish in all dose groups was increased, and their localizations were distinctly different between all dose groups. The ultrastructural changes suggest the progression of mitochondrial vacuolation, especially in the renal tubules, in all dose groups. These results reveal a previously underappreciated effect of dietary oxidized fish oil on channel catfish kidneys. Overall, a series of nutriphysiological responses were adversely affected by exposure to dietary oxidized fish oil, and the corresponding interference patterns on the metabolism and transport of nutrients within cells were observed.     

Effects of dietary choline supplementation on growth performance,lipid deposition and intestinal enzyme activities of blunt snout bream Megalobrama amblycephal fed high‐lipid diet

This study aimed to investigate the effects of dietary choline supplementation on growth, lipid deposition and intestinal enzyme activities of Megalobrama amblycephala. Fish were fed four diets with two lipid levels (50 and 150 g kg^?1) and two choline supplementations (600 and 1600 mg kg^?1) for 8 weeks. Feed conversion ratio (FCR), viscerosomatic index (VSI), hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, whole‐body and muscle lipid contents, intestinal lipase activities and lipoprotein lipase (LPL) activities all increased significantly (P < 0.05) as lipid levels increased, whereas the opposite was true for whole‐body and muscle moisture contents and intestinal amylase activities. VSI, IPF ratio and whole‐body lipid contents all decreased significantly (P < 0.05) with increasing dietary choline supplementations. Weight gain, muscle moisture content all increased significantly (P < 0.05) with increasing dietary choline supplementations when dietary lipid levels reached 150 g kg^?1, whereas the opposite was true for FCR, IPF ratio, IPF and liver LPL activities. In addition, abnormal hepatocytes were found in the liver of fish fed 150 g kg^?1 lipid with 600 mg kg^?1 choline supplementation. The result of this study indicated that extra choline supplementation can improve growth performance, intestinal enzymes activities and reduce excessive lipid deposition of M. amblycephala fed high lipid.     

Effects of dietary protein and lipid levels on growth,feed utilization and body composition in Pseudobagrus ussuriensis fingerlings

An 8‐week feeding trial was conducted to investigate the optimum dietary protein and lipid levels for growth, feed utilization and body composition of Pseudobagrus ussuriensis fingerlings (initial weight: 3.40 ± 0.01 g). Twelve diets containing four protein levels (350, 400, 450 and 500 g kg^?1 crude protein) and three lipid levels (50, 100 and 150 g kg^?1 crude lipid) were formulated. Fish were randomly allotted to 36 aquaria (1.0 × 0.5 × 0.8 m) with 25 fish to each glass aquarium. Fish were fed twice daily (08:00 and 16:00) to apparent satiation. The results showed that weight gain and specific growth rate (SGR) decreased with increasing dietary lipid level from 50 to 150 g kg^?1 at the same dietary protein level. Fish fed the diets containing 150 g kg^?1 lipid exhibited higher feed conversion ratio (P < 0.05), lower protein efficiency ratio (PER) and nitrogen retention efficiency (NRE) relative to fish fed the diet containing 50 and 100 g kg^?1 lipid. Weight gain and SGR significantly increased with increasing dietary protein from 350 to 450 g kg^?1 at the same dietary lipid level, and even a little decline in growth with the further increase in dietary protein to 500 g kg^?1. Daily feed intake, NRE and PER were significantly affected by both dietary protein and lipid levels (P < 0.05) and tended to decrease with increasing dietary protein and lipid levels. Whole‐body protein content increased as protein levels increased and lipid levels decreased. Whole‐body lipid and muscle lipid content increased with increasing dietary lipid level, and decreased with increasing dietary protein at each lipid level. There was no significant difference in condition factor and viscerosomatic index among fish fed the diets. Hepatosomatic index was affected by dietary lipid level (P < 0.05), and increased with increasing dietary lipid level at the same protein level. These results suggest that the diet containing 450 g kg^?1 protein and 50 g kg^?1 lipid with a P/E ratio of 29.1 mg protein kJ^?1 is optimal for growth and feed utilization of P. ussuriensis fingerlings under the experimental conditions used in the study.     

Effect of oxidized fish oil on growth performance and oxidative stress of Litopenaeus vannamei

A 4‐week feeding trial was conducted to determine the effects of oxidized fish oil (OFO, POV: 234.84 meq kg^?1) on growth performance and oxidative stress of Litopenaeus vannamei. Five diets containing various OFO levels (0, 25, 50, 75 and 100 g kg^?1) with the same dietary lipid level were fed to L. vannamei. The results showed that the body weight gain and the specific growth rate of the shrimp fed with 50, 75 and 100 g kg^?1 of OFO diets decreased significantly (P < 0.05), whereas the hepatosomatic index increased significantly (P < 0.05). The malondialdehyde concentrations in the serum and muscle of the shrimp fed with 50, 75 and 100 g kg^?1 of OFO diets were significantly higher than that of the shrimp fed with fresh fish oil (P < 0.05). The total antioxidant competence decreased significantly compared with the control group. Therefore, dietary OFO affects the growth performance and increases the oxidative stress of shrimp.     

The effects of Spirulina platensis meal on proximate composition,fatty acid profile and lipid peroxidation of rainbow trout (Oncorhynchus mykiss) muscle

This study evaluated the effects of diets containing 0, 25, 50, 75 and 100 g kg^?1 Spirulina platensis on proximate composition, fatty acid profile and lipid peroxidation of rainbow trout (Oncorhynchus mykiss). Supplementation of S. platensis did not change moisture and protein contents, but fish fed 50 and 100 g kg^?1 S. platensis had lower muscle lipid content than those fed control diet (P < 0.05). Fish fed 100 g kg^?1 of S. platensis contained lower percentages of saturated and monounsaturated fatty acid and a higher percentage of polyunsaturated fatty acid than those fed control diet (P < 0.05). The n‐3/n‐6 ratio of the fatty acid increased and muscle atherogenic and thrombogenic indices were significantly decreased as the dietary supplement of S. platensis increased. Furthermore, lipid peroxidation of the fillet significantly decreased with increasing dietary S. platensis at 4 °C and at ?20 °C (P < 0.05). The results of this study show that supplementation of S. platensis to the diet improves muscle quality of the rainbow trout.     

Effects of dietary phosphorus on growth,body composition and immunity of young taimen Hucho taimen (Pallas, 1773)

The effects of dietary phosphorus (P) on growth, body composition and immunity of young taimen (Hucho taimen) were studied. Six purified diets contained graded levels (2.3‐control, 4.0, 5.6, 7.5, 9.1 and 10.8 g kg^?1 diet) of available P. Each diet was fed to triplicate groups of 30 fish with an initial average weight (55.31 ± 0.38) g for 84 days. The weight gain, specific growth rate and feed conversion ratio were improved by dietary available P up to 4.35 g kg^?1 (P < 0.05) and then levelled off. Hepatosomatic index and body crude lipid content decreased significantly with increasing P levels, while ash contents and P concentrations in the whole body and vertebrae increased by dietary available P up to 4.36 and 4.44 g kg^?1 and then levelled off respectively (P < 0.05). Liver superoxide dismutase and glutathione peroxidase and plasma alkaline phosphatase activities in the treatment groups were significantly higher compared with the control group (P < 0.05). Plasma IgM contents increased linearly with increasing dietary P from 4.0 to 9.1 g kg^?1 group and then decreased. Dietary P supplementation reduced plasma triglyceride, malondialdehyde and liver malondialdehyde contents. There were no significant effects on plasma total protein, albumin, globulin, glucose, aspartate aminotransferase and alanine aminotransferase, catalase, lysozyme and liver catalase compared with the control group (P > 0.05). Broken line regression analysis indicated that dietary available P requirement was 4.34 and 4.35 g kg^?1, based on weight gain and P concentration in the whole body respectively.     

The effects of dietary lipid levels on performance and heat‐shock protein response of juvenile white seabass,Atractoscion nobilis

A feeding trial was conducted to study the effect of dietary lipid on growth performance and heat‐shock protein (HSP70 and HSP60) response of white seabass (WSB), Atractoscion nobilis. Five diets were formulated to contain 440 g kg^?1 protein from 300 g kg^?1 fish meal, 240 g kg^?1 soybean meal and 100 g kg^?1 soy protein concentrate with different levels of lipid: 100, 120, 140, 160 or 180 g kg^?1. At the end of the trial, heat shock response based on HSP70 and HSP60 was measured in liver and white muscle from fish at ambient temperature and temperature shock conditions. Final weight and percent gain were significantly higher for fish fed the 100 g kg^?1 lipid diet than for fish fed the rest of the diets (P ≤ 0.05). Feed conversion ratio was lowest for fish fed the 100 g kg^?1 lipid diet. The HSP70 and HSP60 responses were positively correlated to dietary lipid levels following temperature shock. At ambient temperature, HSP60 and HSP70 responses in muscle and HSP60 response in liver increased with dietary lipid level. Temperature shock significantly increased the HSP response of fish in all treatments. Results of this study demonstrated that a moderate (110–120 g kg^?1) level of dietary lipids would be recommended for production diets but a higher dietary lipid level may be required for optimal stress tolerance.     

Comparative study on dietary protein requirements for juvenile and pre‐adult gibel carp (Carassius auratus gibelio var. CAS III)

Two 8‐week growth trials were conducted in indoor recirculation system to evaluate the protein requirements for juvenile (3.70 ± 0.20 g) and pre‐adult (85.2 ± 0.70 g) gibel carp, Carassius auratus gibelio var. CAS III. Six isoenergetic diets were formulated for each trial using fish meal and casein as protein sources, and protein level was 250–450 g kg^?1 in Trial 1 and 200–450 g kg^?1 in Trial 2. With the increasing dietary protein, feeding rate (FR) and feed conversion ratio (FCR) significantly decreased (P < 0.05). Weight gain (WG) increased first and then reached a plateau in 330–450 g kg^?1 in Trial 1 (P > 0.05), while decreased after the maximum value in 350 g kg^?1 in Trial 2 (P < 0.05). Productive protein values (PPVs) were lower in 370–450 g kg^?1 in Trial 1 and 400–450 g kg^?1 in Trial 2 (P < 0.05). Increasing dietary protein level increased protein content and decreased lipid content in whole fish body and white muscle (P < 0.05). Apparent digestibility coefficient of dry matters (ADC_d) decreased, while apparent digestibility coefficient of protein (ADC_p) increased in 370–450 g kg^?1 in Trial 1 and 250–450 g kg^?1 in Trial 2 (P < 0.05). Trypsin activity significantly increased in 370–450 g kg^?1 in Trial 1 (P < 0.05) and was not affected in Trial 2 (P > 0.05). Hepatic alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in both trials increased when dietary protein was above 400 g kg^?1 (P < 0.05). Based on quadratic regression of WG, it was estimated that dietary protein requirement for maximum growth was 414 g kg^?1 (digestible protein of 376 g kg^?1) and 365 g kg^?1 (digestible protein of 324 g kg^?1) for juvenile (3.70 g) and pre‐adult gibel carp (85.2 g).     

Growth,feed utilization and body composition of juvenile Manchurian trout,Brachymystax lenok (Pallas) fed different dietary protein and lipid levels

A 10‐week feeding trial with four dietary protein levels (400, 450, 500 and 550 g kg^?1 crude protein) and two dietary lipid levels (80 and 160 g kg^?1 crude lipid) was conducted to assess optimum dietary protein and lipid levels for the growth, feed utilization and body composition of juvenile Manchurian trout (initial weight 11.80 ± 0.15 g). Fish were fed twice daily (08:30 and 16:30 h) to apparent satiation. The results showed that fish fed the diet with 500 g kg^?1 protein and 80 g kg^?1 lipid had the highest growth and feed efficiency. However, fish fed the diet with 450 g kg^?1 protein and 160 g kg^?1 lipid showed comparable growth to that of the fish fed diet 5 (500/80) and had higher protein efficiency ratio (PER), nitrogen retention (NR) and energy retention (ER) than other groups (P < 0.05). Growth, PER, NR and ER of fish fed the 160 g kg^?1 lipid diet was significantly higher (P < 0.05) than that of fish fed the 80 g kg^?1 lipid diet at 400 and 450 g kg^?1 protein diet, whereas these values showed an opposite trend at 500 and 550 g kg^?1 protein diet, and the lowest PER, NR and ER was found by fish fed the 400 g kg^?1 protein diet with 80 g kg^?1 lipid. Fish fed diets with 400 g kg^?1 protein had lower feed intake (FI) than that of other groups. Feed intake of fish fed 80 g kg^?1 lipid level was significantly lower than that of fish fed 160 g kg^?1 lipid diet at 400 g kg^?1 protein (P < 0.05), while no significant differences were observed at 450, 500 and 550 g kg^?1 protein‐based diets. Contrary to moisture content, lipid content of whole body and muscle increased significantly (P < 0.05) with increasing lipid levels. The results of this study indicated that the diet containing 450 g kg^?1 protein and 160 g kg^?1 lipid, with a P/E ratio of 23.68 g protein MJ^?1 would be suitable for better growth and feed utilization of juvenile Manchurian trout under the experimental conditions and design level used in this study.     

Effect of lipid levels on the reproductive performance of Snakehead murrel,Channa striatus

Present study aimed to determine the optimum dietary lipid level in snakehead murrel channa striatus broodstocks. Triplicate groups of fish were fed for 240 days with isonitrogenous experimental diets with increasing lipid levels (100, 140, and 180 g kg^?1), using fish oil and soybean oil as the lipid sources with the ratio of (1:1). Weight gain, GSI, fecundity, oocyte diameter and number of mature oocyte were found to be significantly higher in the group fed with diet containing 180 g kg^?1 lipid level. Muscle fatty acid profile showed a significant increase in LA (18:2n‐6), LNA (18:3n3), total PUFA, n‐6 and ArA (20:4n‐6) in fish fed with diet containing 180 g kg^?1 lipid. Increasing lipid level up to 180 g kg^?1 resulted in significant increase in PUFA (LA & LNA), lc‐PUFA (EPA, DHA, ArA), total PUFA, n‐3 and n‐6 series in ovary and liver of female C. striatus.     

Optimal dietary methionine requirement of juvenile Chinese sucker,Myxocyprinus asiaticus

A total of 630 juvenile Chinese sucker, with an average initial weight of 1.72 ± 0.05 g, were fed seven diets for 56 days to study the effect of dietary methionine levels on growth, feed utilization, body composition and haematological parameters on juvenile Chinese sucker. Diet 1 using fish meal as the sole protein source and diets 2–7 using fish meal and fermented soybean meal as intact protein sources supplemented with crystalline amino acids contained six levels of l ‐methionine ranging from 6.4 to 18.9 g kg^?1 of dry diet at a constant dietary cystine level of 3.7 g kg^?1. Each diet was randomly assigned to three aquaria. Results indicated that the highest weight gain, specific growth rate (SGR), feed efficiency ratio, protein efficiency ratio and protein productive value occurred at 13.9 g methionine kg^?1 diet among the methionine supplemented dietary groups, beyond which they showed declining tendency. The whole body and muscle protein contents of juvenile Chinese sucker were positively correlated with dietary methionine level, while muscle lipid content was negatively correlated with it. The total essential amino acids content of muscle was increased significantly with increasing dietary methionine level from 6.4 to 13.9 g kg^?1 (P < 0.05). Apparent digestibility coefficients of dietary protein were significantly affected by dietary treatments. Serum protein, cholesterol and triacylglycerol increased with increasing dietary methionine levels, but showed a relatively lower value for fish fed the 18.9 g methionine kg^?1 diet. Quadratic regression analysis of SGR against dietary methionine level indicated that optimal dietary methionine requirement for juvenile Chinese sucker was 14.1 g kg^?1 of the diet in the presence of 3.7 g kg^?1 cystine (corresponding to 32.0 g kg^?1 of dietary protein on a dry‐weight basis).     

Effect of dietary protein levels on reproductive development and distribution of amino acids in the body tissues of female Pangasianodon hypophthalmus (Sauvage, 1878) broodstock in captivity

The present study investigated the optimum dietary protein level for the maturation of adult Pangasianodon hypophthalmus broodstock. Four isocaloric diets containing 250, 300, 350 and 400 g kg^?1 of protein levels were prepared and presented to triplicate groups of fish. The fish (mean weight 770 ± 17.23 g and 712 ± 23.42 g for females and males respectively) were stocked in outdoor canvas tanks (4 m × 1 m × 1 m) at a stocking density of 20 fish/tank with a male: female ratio of 1:4. The fish were fed the test diets to satiation twice daily for 6 months. Gonadosomatic index (GSI) and fecundity were similar among fish fed dietary protein levels, higher than those fed on the 250 g kg^?1. Final weight, weight gain, oocyte weight were significantly highest (P < 0.05) for the fish fed 350 and 400 g kg^?1 dietary protein treatments. Only the 350 g kg^?1 dietary protein treatment resulted in significantly best ovipositor diameter and % ripe egg. Amino acid levels were highest in the muscle followed by the oocyte and liver of fish fed 350 and 400 g kg^?1 dietary protein levels. The present results suggested that a dietary protein level of 350 g kg^?1 can be recommended for the development of P. hypophthalmus broodstock.     

Digestibility of energy,lipids and fatty acids of vegetable oils and poultry fat by pacu Piaractus mesopotamicus (Holmberg 1887)

Evaluation of vegetable oils and poultry fat digestibility is the first step to elicit their use in aquafeeds. This work aimed at determining apparent digestibility coefficients (ADCs) of energy, lipids and fatty acids of oil sources for pacu, a widely farmed neotropical Characin. A semipurified, omnivorous fish diet (344.2 g kg^?1 crude protein; 18.16 MJ kg^?1 gross energy) was used as reference diet. Test diets were obtained by adding 2 g kg^?1 chromium III oxide and replacing 15 g kg^?1 reference diet with fish, soybean, colza, corn and flaxseed oils and poultry fat. Juvenile pacu (64 ± 10.8 g; 14.6 ± 1.1 cm) were fed to apparent satiety, four times a day, and then transferred to cylindrical–conical aquaria for collection of faeces by sedimentation (n = 3). Apparent digestibility coefficients of energy and lipids were high for all tested oils (P > 0.05); ADCs of saturated fatty acid (SFA) were lower than monounsaturated fatty acids (MUFA) and polyunsaturated fatty acid (PUFA). Essential fatty acids (18:2n‐6 and 18:3n‐3) had high ADC (>93%), colza oil and poultry fat yielding the lowest ADC for 18:2n‐6 (P = 0.01) and 18:3n‐3 (P < 0.01), respectively. Corn oil, soybean oil and flaxseed oil were interesting sources of 18:2n‐6 and 18:3n‐3 dietary fatty acids for pacu.     

Dietary choline requirement for juvenile blunt snout bream,Megalobrama amblycephala

A 12‐week feeding trial was conducted to determine dietary choline requirement for juvenile Megalobrama amblycephala. The basal diet was formulated to contain 310 g kg^?1 diet from vitamin‐free casein and gelatine. Choline chloride was supplemented to the basal diet to formulate six purified diets containing 0, 250, 500, 1000, 2000 and 4000 mg kg^?1, respectively. Each diet was randomly fed to quadrupled groups of Megalobrama amblycephala with initial average weight 1.84 ± 0.04 g in a flow‐through system. Results showed weight gain was increased significantly with increasing dietary choline levels (P < 0.01). Lipid content of liver decreased significantly as dietary choline concentration increased (P < 0.01), whereas lipid content of dressed carcass showed opposite trend (P < 0.01), and lipid content of whole‐body was unaffected by dietary choline supplementation. Broken‐ line regression of weight gain, liver and muscle choline concentration showed choline requirements of Megalobrama amblycephala of 1198, 1525 and 1365 mg kg^?1, respectively. In addition, dietary choline supplementation significantly improved lipid content of dressed carcass but not the content of whole body of blunt snout bream.     

Conjugated linoleic acid affects growth performance,hepatic fatty acid profile and lipid metabolism in juvenile Synechogobius hasta

This study was conducted to determine the effect of dietary CLA (Conjugated linoleic acid) levels on growth performance, fatty acid profiles and lipid metabolism of liver in Synechogobius hasta. Fish were fed six diets with fish oil replaced by 0 (control), 5, 10, 15, 20 and 25 g kg^?1 CLA for 8 weeks. Weight gain, WG, and SGR (specific growth rate) tended to increase when dietary CLA levels increased from 0 to 10 g kg^?1 and then decline with further increasing dietary CLA levels to 25 g kg^?1. FCR (feed conversion ratio) showed contrary trend with WG and SGR. The reduced VSI (vicero somatic index) and increased HSI (hepatosomatic index) were observed in fish fed increasing dietary CLA levels. Whole‐body lipid content declined, but hepatic lipid content increased with increasing dietary CLA levels. Dietary CLA modified total percentages of the main groups of fatty acids in liver. Hepatic 6PGD, ME and ICDH activities increased with increasing dietary CLA levels. FAS and G6PD were very variable and not related to dietary treatments. CPT I activities showed no significant differences among the treatments. Based on second‐order polynomial regression analysis of WG and FCR against dietary CLA level, 8.7–10.1 g kg^?1 was indicated to be the optimal dietary CLA range for maximum growth and feed utilization for S. hasta.     

Quantitative dietary leucine requirement of juvenile Pacific white shrimp,Litopenaeus vannamei (Boone) reared in low‐salinity water

The experiment was conducted to determine the leucine requirement of juvenile Pacific white shrimp Litopenaeus vannamei (Boone) in low‐salinity water (0.50–1.20 g L^?1). Six diets were formulated to contain 410 g kg^?1 crude protein with fish meal, peanut meal and precoated crystalline amino acids with different concentration of l ‐leucine (16.72, 19.60, 22.06, 24.79, 27.28 and 30.16 g kg^?1 dry diet). Each diet was randomly assigned to triplicate groups of 30 shrimps (0.38 ± 0.002 g), and the feed trial lasted for 8 weeks. The results indicated that the maximum weight gain was observed at 24.95 g kg^?1 dietary leucine group, whereas the diets containing higher leucine concentration conversely reduced the growth performance (P < 0.05). Moreover, the highest body protein content and body protein deposition and the lowest haemolymph AST and ALT activities were also found at 24.95 g kg^?1 dietary leucine group. With the increase in leucine in diets, a dose‐dependent increase was found in body lipid content and haemolymph urea concentration. The polynomial regression calculated using weight gain, feed efficiency and body protein deposition indicated that the optimal dietary leucine requirement for L. vannamei reared in low‐salinity water was 23.73 g kg^?1 leucine of dry diet, correspondingly 57.88 g kg^?1 of dietary protein.     

Effects of dietary microbial levan on growth performance,RNA/DNA ratio and some physio‐biochemical responses of Labeo rohita (Hamilton) juveniles

Six isonitrogenous and isocaloric semi‐purified diets were prepared with different levels of microbial levan: control (Basal), T1 (Basal + 2.5 g kg^?1 diet), T2 (Basal + 5 g kg^?1 diet), T3 (Basal + 7.5 g kg^?1 diet), T4 (Basal + 10 g kg^?1 diet) and T5 (Basal + 12.5 g kg^?1 diet), fed to six groups of fish in triplicate tanks. The results of the 60 days feeding trail showed that supplementation of dietary levan significantly affected the weight gain percentage and specific growth rate of the treatment groups fed at 10 g kg^?1 or more levan. Lowest feed conversion ratio (FCR) value and highest survival percentage among levan fed groups were observed with 12.5 g kg^?1 incorporation (T5) and was comparable with (T4) group. Significant increase in muscle RNA level and RNA/DNA ratio was observed with the increasing dietary levan. Fish fed 12.5 g kg^?1 levan had significantly higher protease, amylase and lipase activities compare with the control group. Lowest Aspartate aminotransferase (AST) activity in the liver and muscle was observed in the T5 group fed with highest level of dietary levan. Overall results conclude that dietary microbial levan incorporation at 12.5 g kg^?1 could be used as potent dietary prebiotic for the culture of L. rohita juveniles.     

Effects of dietary nucleotides on growth,physiological parameters and antioxidant responses of Juvenile Yellow Catfish Pelteobagrus fulvidraco

The effects of nucleotides on growth, and physiological and antioxidant parameters were evaluated by feeding Pelteobagrus fulvidraco diets supplemented with 0, 0.2, 0.4, 0.6, 1.0 or 1.5 g kg^?1 of nucleotides respectively. All nucleotide groups showed higher specific growth rate, feed efficiency, protein efficiency ratio, whole‐body lipid content and serum cholesterol concentrations than the control group, but the significant difference was seen only between fish from the 1.5 g kg^?1 nucleotide group and fish from the control group. Whole‐body ash content in fish from the 0.6 g kg^?1 nucleotide group, and liver superoxide dismutase and catalase in fish from the 0.4 g kg^?1 nucleotide group were significantly higher than those in fish from the control group. Respiratory burst activity was significantly higher in fish from the 0.6, 1.0 and 1.5 g kg^?1 nucleotide groups than in fish from the control. This finding was accompanied by lower liver concentrations of thiobarbituric acid‐reacting substances in fish from the same groups compared to those from the control group. The results indicate that dietary nucleotides could improve growth and antioxidant responses in juvenile yellow catfish.     

Effects of dietary lipid level on growth performance,body composition and digestive enzymes activity of juvenile sea cucumber,Apostichopus japonicus

A feeding trial aimed to determine the effects of dietary lipid level on growth performance, body composition and digestive enzymes activity of juvenile sea cucumber, Apostichopus japonicus. Diets with six crude lipid levels (1.9, 13.8, 29.1, 43.6, 59.6 and 71.6 g kg^?1) were fed to sea cucumbers (initial weights 0.65 ± 0.01 g) at a density of 30 juveniles, once a day. After 60 days, body weight gain (BWG), specific growth rate (SGR), feed intake (FI) and protein efficiency ratio (PER) decreased with increasing dietary lipid levels. The sea cucumbers fed 1.9 g kg^?1 crude lipid showed significantly higher (P < 0.05) BWG than those of the sea cucumbers fed 59.6 and 71.6 g kg^?1 crude lipid. Intestinal protease and lipase activities generally increased with increasing dietary lipid levels. Eicosapentaenoic acid (EPA) content of body walls generally increased with increasing dietary lipid levels. Docosahexaenoic acid (DHA) content of body walls reached the maximum value at a dietary lipid level of 13.8 g kg^?1. N‐3 highly unsaturated fatty acid content followed the same pattern of DHA. According to the growth performance and body composition of sea cucumbers, it can be indicated that the optimum dietary lipid level for juvenile sea cucumbers is between 1.9 and 13.8 g kg^?1.     

Optimum dietary protein level for growth and coelomic fluid non‐specific immune enzymes of sea cucumber Apostichopus japonicus juvenile

A feeding trial was conducted to determine the optimum dietary protein level of sea cucumber Apostichopus japonicus juvenile focusing on growth performance and non‐specific immune response. Diets with seven crude protein levels (42.0, 108.9, 155.2, 216.7, 258.0, 313.3 and 357.5 g kg^?1) were fed to sea cucumber juveniles (1.05 ±0.01 g) once a day for 100 days. More than 70% survival was observed, and there was no significant difference among all treatments. The sea cucumbers fed diets containing 108.9 g kg^?1 crude protein showed significantly (P < 0.05) higher body weight gain than those of the sea cucumbers fed diets containing 42.0, 216.7, 258.0, 313.3 and 357.5 g kg^?1 crude protein. No significantly differences (P > 0.05) were observed in moisture, crude protein, crude lipid, ash and carbohydrate content of the body wall among all treatments. The coelomic fluid catalase activity of the sea cucumbers generally increased with increasing dietary protein levels. Therefore, the acid phosphatase, superoxide dismutase and lysozyme activity increased with increasing dietary protein levels at first and decreased subsequently. The relationship between dietary protein levels and body weight gain was analysed by a second‐order polynomial regression analysis model. The result indicates that the optimum dietary protein level for sea cucumber juveniles is 135.4 g kg^?1.