Effects of dietary chlorogenic acid on growth,flesh quality and serum biochemical indices of grass carp (Ctenopharyngodon idella)

The study was to investigate effects of dietary chlorogenic acid (CGA) on growth performance, flesh quality and serum biochemical indices of grass carp (95.1 ± 0.3 g) (Ctenopharyngodon idella) fed seven different diets, including control diet, Eucommia ulmoides (EU)‐supplemented diet (20 g kg^–1) and CGA‐supplemented diets containing 100, 200, 400, 600 and 800 mg/kg CGA. Contents of collagen and alkaline‐insoluble collagen in muscle and skin were significantly increased by dietary CGA and EU (p < .05). Total essential amino acids (TEAA) and total amino acids (TAA) in muscle of grass carp fed EU diet or 400, 600 and 800 mg/kg CGA diet were significantly higher than those of fish fed control diet and 100 and 200 mg/kg CGA diet (p < .05). Fish fed 200–800 mg/kg CGA showed significantly lower muscle crude lipid content than EU, control and 100 mg/kg CGA groups (p < .05). Fish fed CGA‐supplemented diets (100–800 mg/kg) had significantly higher muscle fibre density and lower muscle fibre diameter than control group (p < .05). In conclusion, supplementation of CGA improved flesh quality of grass carp, and supplemental level of CGA for improving flesh quality and growth was estimated to be 400 mg/kg diet.     

Prebiotics effect on growth performance,hepatic intermediary metabolism,gut microbiota and digestive enzymes of white sea bream (Diplodus sargus)

This study aimed at evaluating the effects of short‐chain fructooligosaccharides (scFOS), xylooligosaccharides (XOS) and galactooligosaccharides (GOS) on growth performance, hepatic metabolism, gut microbiota and digestive enzymes activities of white sea bream juveniles. Four diets were formulated: a control diet with fish meal (FM) and plant feedstuffs (PF) (30FM:70PF) and three test diets similar to control but supplemented with 10 g of scFOS, XOS or GOS per kilo diet, which were fed to fish during 12 weeks. Prebiotics had no effect on growth, feed efficiency or gut microbiota. Plasmatic triglycerides were lower in fish fed XOS than FOS and GOS diets. Malic enzyme activity was lower in fish fed XOS than FOS diet. Fish fed XOS diet had lower fatty acid synthetase (FAS), a key lipogenic enzyme and higher alanine aminotransferase activities. Fifteen days after the start of the trial, an enhancement of total alkaline protease, trypsin and lipase activities was observed in fish fed prebiotics, but such effect disappeared at 12 weeks. In conclusion, scFOS, XOS or GOS seem to have limited applicability in white sea bream feed.     

Dietary organic acid salts mitigate plant protein induced inflammatory response and improve humoral immunity,antioxidative status and digestive enzyme activities in yellowfin seabream,Acanthopagrus latus

An eight‐week research was conducted to investigate the effects of single or combined administration of sodium propionate (Na‐P) and sodium acetate (Na‐A) on the performance of yellowfin seabream (Acanthopagrus latus) juveniles (6.5 ± 0.3 g). A plant protein (PP)‐rich diet was supplemented with sole or blends of organic acid salts (OAS) namely Na‐P and Na‐A to design six experimental feeds including control (without OAS), Na‐P5 (5 g/kg Na‐P), Na‐P10 (10 g/kg Na‐P), Na‐A5 (5 g/kg Na‐A), Na‐A10 (10 g/kg Na‐A) and Na‐P + A (5 g/kg Na‐P + 5 g/kg Na‐A). Except for Na‐A5 group, the other OAS‐supplemented treatments had higher growth and feed efficiency ratio than the control (p < .05). The inclusion of OAS in the experimental feeds pronouncedly enhanced plasma lysozyme and alternative complement pathway activities compared to the control. Furthermore, fish fed on the OAS‐supplemented diets had greater catalase and glutathione peroxidase activities in the liver than the control (p < .05). Total antioxidant capacity in the liver of fish fed on the OAS‐supplemented diet also was higher than the control. Fish fed on the OAS‐supplemented diets had higher pepsin, trypsin and lipase activities than the control. The insulin‐like growth factor 1 (IGF‐1) gene expression was remarkably down‐regulated in the liver of fish fed on the OAS‐supplemented diets compared to the control especially in groups fed on the Na‐P10 and Na‐A10 diets. The greatest IGF‐1 gene down‐regulation level in the gut was in fish fed on the Na‐P5 and Na‐P10 diets. The interleukine‐1β in the gut was remarkably up‐regulated in the control compared to the other groups (p < .05). The lactic acid bacterial colonies count in the gut of the control was lower than the OAS‐supplemented groups. Based on the findings of the present study, supplementing PP‐rich diets with 10 g/kg Na‐P or blends of Na‐P (5 g/kg) and Na‐A (5 g/kg) beneficially alleviated inflammatory responses and improved immune parameters and digestive capacity in yellowfin seabream juveniles.     

Effects of gelatin or carboxymethyl cellulose supplementation during pelleting processing on feed quality,intestinal ultrastructure and growth performance in gibel carp (Carassius gibelio)

Gelatin and carboxymethyl cellulose (CMC) were often used as binders due to their binding ability. To investigate the effects of gelatin and CMC supplementation on feed quality, intestinal ultrastructure and growth performance of gibel carp, six pelleted feed were formulated: control; supplemented with gelatin (10 g/kg, 30 g/kg and 50 g/kg); and supplemented with CMC (10 g/kg and 30 g/kg). Increased gelatin supplementation levels reduced feed solubility and pellet softening (p < .05) and decreased chemical oxygen demand in the surrounding water after pellets were immersed (p < .05). Increased levels of gelatin supplementation enhanced digesta viscosity and reduced intestinal microvilli length and digestive enzymes activities (chymotrypsin and amylase; p < .05) of fish. Fish‐fed diets supplemented with 30 g/kg gelatin had higher levels of plasma total free amino acids and glucose (p < .05) than fish fed 10 g/kg and 50 g/kg gelatin. Feed supplemented with 10 g/kg CMC were softer than those supplemented with 30 g/kg CMC (p < .05); fish‐fed diets supplemented with 10 g/kg CMC had longer intestinal microvilli (p < .05) than fish fed 30 g/kg CMC. Thus, our results indicated that either gelatin or CMC is applicable to supplement in the feed for improving feed quality and without negative effect on growth performance of gibel carp.     

A combination of rapeseed,cottonseed and peanut meal as a substitute of soybean meal in diets of Yellow River carp Cyprinus carpio var

A feeding trial was conducted to evaluate the results of replacing soybean meal (SBM) with other blend plant protein (BP) (rapeseed meal, cottonseed meal and peanut meal) sources on growth, fish body composition, biochemical parameters, non‐specific immune index and gene expression of growth hormone/insulin‐like growth factor‐1 in Yellow River carp Cyprinus carpio. The results showed that the 600 g/kg replacement with BP in diet did not affect the growth performance of Yellow River carp, but the 800 g/kg SBM replacement diet could depress the growth of fish (p < .05). The 800 g/kg SBM replacement diet significantly impacted the superoxide dismutase, malondialdehyde contents, lysozyme, alanine aminotransferase and aspartate aminotransferase activities (p < .05). Fish fed 800 g/kg SBM replacement diet showed lowest insulin‐like growth factor 1 and highest growth hormone level than that of other diets (p < .05). Both gene expression levels of GH and IGF‐I in hepatic showed significant difference among dietary treatments (p < .05), and the lowest GH and IGF‐I mRNA level in liver were found in fish fed 800 g/kg SBM replacement diet (p < .05). In conclusion, no more than 600 g/kg SBM could be replaced by BP in diet of Yellow River carp without adverse effects on the growth performance. However, 800 g/kg SBM replacement with BP in diet inhibited the growth performance, affected some blood parameters and immune response index, and down‐regulated GH and IGF‐1 gene expression of liver in Yellow River carp. Further, GH level in serum was negatively correlated with GH mRNA level in liver; meanwhile, serum concentrations of IGF‐I were positively correlated with hepatic IGF‐I mRNA expressions.     

Effects of α‐lipoic acid on growth performance,body composition,antioxidant profile and lipid metabolism of the GIFT tilapia (Oreochromis niloticus) fed high‐fat diets

The wide use of lipid as a non‐protein energy substitute has led to lipid metabolic problems in cultured tilapia. Therefore, studies that reduce the effects of high‐fat diets in genetically improved farmed tilapia (GIFT) are required. This study evaluated the optimum level and effects of dietary α‐lipoic acid (α‐LA) on growth performance, body composition, antioxidant capacity and lipid metabolism of GIFT tilapia. The basal diet (120 g/kg lipid) was supplemented with six concentrations of α‐LA at 0 (control), L300, L600, L900, L1200 and L2400 mg/kg diet to make the experimental diets, which were fed to GIFT tilapia juveniles (initial body weight: 0.48 ± 0.01 g) for 8 weeks. The weight gain of fish improved significantly in the L300 than other dietary treatments. The intraperitoneal fat index and lipid content of fish fed on the L2400 diet decreased significantly than those fed on the control diet. The activities of superoxide dismutase and glutathione peroxidase (GSH‐Px) in serum and liver were significantly higher in fish fed on the L300 diet than the control. The reduced GSH content of fish fed on the L300 in serum and liver was significantly higher than those fed on control diet. The malondialdehyde content in serum and liver was significantly lower in L300 than in the control. The adipose triglyceride lipase gene was significantly up‐regulated in fish fed on the L2400, but the diacylglycerol acyltransferase 2 gene was down‐regulated in adipose. The liver‐type fatty acid‐binding protein gene in the liver was significantly up‐regulated in fish fed on the L300 and L600 diets. Moreover, the acyl‐coenzyme A oxidase gene in liver was significantly up‐regulated in fish fed on the L300, L600, L900 and L1200 diets. Polynomial regression analysis indicated that 439–528 mg/kg α‐LA is an appropriate dosage in high‐fat diet to improve growth performance and relieve lipid oxidative damage by accelerating lipid catabolism and reducing lipid synthesis in GIFT tilapia.     

Effect of dietary chromium picolinate on growth performance and blood parameters in grass carp fingerling, <Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>

An experiment was conducted to investigate the effect of dietary chromium picolinate supplement on growth and haematology parameters of grass carp, Ctenopharyngodon idellus. Six diets with increasing dietary chromium picolinate levels 0, 0.2, 0.4, 0.8, 1.6 and 3.2 mg kg⁻¹ were fed to triplicate groups of 20 fish (initial weight of 12.78 ± 1.16 g, mean ± SD) in a flow water system for 10 weeks. Fish fed the diet supplemented with 0.8 mg Cr kg⁻¹ had significantly improved weight gain (WG), feed efficiency ratio (FER), protein efficiency ratio (PER) and protein retention (PR). Fish fed high-chromium diets exhibited lower whole-body crude lipid contents than fish fed low-chromium diets. Liver glycogen concentrations for fish fed the diet with 0.2 mg Cr kg⁻¹ was the highest (77.67 mg g⁻¹). Fish fed the diet supplemented with 1.6 and 3.2 mg Cr kg⁻¹ had significantly lower liver glycogen concentrations than other groups (P < 0.05). The highest serum insulin concentrations were observed in fish fed the diet supplemented with 0.8 mg Cr kg⁻¹, but serum insulin concentrations decreased (P < 0.05) when dietary supplementation of chromium was higher than 0.8 mg Cr kg⁻¹. Cholesterol concentrations decreased in direct proportion to dietary chromium level and achieved the lowest level when the fish were fed the 0.8 mg Cr kg⁻¹ diet, but increased when the fish were fed the diet with more than 0.8 mg Cr kg⁻¹ (P < 0.05). Fish fed the diet supplemented with 0.8 mg Cr kg⁻¹ had higher triglyceride and high-density lipoprotein cholesterol (HDL-C) concentrations compared to other treatments. The results of the present study suggested that chromium picolinate could modify serum carbohydrate and lipid metabolism profile, and that the optimal dietary chromium level was 0.8 mg kg⁻¹ for grass carp according to growth.     

Effects of dietary supplementation with coconut oil on the growth,fatty acid profiles and some lipid metabolism relative gene expressions of orange‐spotted grouper Epinephelus coioides

This study investigated the effects of coconut oil as a dietary supplement on the growth, lipid metabolism and related gene expressions of juvenile orange‐spotted grouper Epinephelus coioides. Coconut oil at concentrations of 0, 10, 30 and 50 g/kg was used to replace dietary lipids in a basal diet containing 150 g/kg lipids. The four experimental diets were, respectively, fed to triplicate groups of juvenile groupers (initial weight: 8.53 ± 0.13 g) in a recirculating system for 8 weeks. Fish fed the diet containing 50 g/kg coconut oil exhibited lower (p < .05) weight gain than did fish fed the diet containing 30 g/kg coconut oil; however, no significant differences in weight gain were observed between fish fed diets containing 0 and 10 g/kg coconut oil. Hepatic carnitine palmitoyltransferase‐1, fatty acid synthase, fatty acid elongase, fatty acid desaturase and peroxisome proliferator‐activated receptor gamma gene expressions were all the highest in fish fed the diet containing 10 g/kg coconut oil. Fish fed the coconut oil‐free basal diet demonstrated upregulated gene expression of neuropeptide Y. The results suggest that dietary supplementation with 10 g/kg coconut oil exerted beneficial effects on lipid metabolism by E. coioides.     

Interactive effects of coffee bean supplementation and waterborne zinc toxicity on growth performance,biochemical variables,antioxidant activity and zinc bioaccumulation in whole body of common carp,Cyprinus carpio L.

Roasted coffee powder (RCP; Coffea arabica) is usually used as a beverage for human but there are few attempts to use it as a natural feed supplement in fish diets. In this study, common carp, Cyprinus carpio L., (11.8 ± 0.09 g) were reared in zinc (Zn)‐containing water at concentrations of 0.0 or 5.0 mg/L and cosupplemented with 0.0 or 1.0 g RCP/kg diet for 6 weeks to investigate effects of RCP supplementation, Zn exposure and their interaction on fish performance, biochemical variables, antioxidant activity and Zn bioaccumulation in whole fish body. Fish growth and feed intake were significantly affected by RCP supplementation, Zn toxicity and their interaction. However, fish fed a RCP‐supplemented diet did not exhibit better performance than those fed the RCP‐free diet and both diets produced higher fish performance than the Zn‐toxicated fish. It is noticed that RCP supplementation to Zn‐toxicated fish enhanced their growth, and feed utilization as compared to Zn‐toxicated fish alone. Fish fed control and RCP‐enriched diets showed no significant differences in biochemical variables, which were significantly altered due to waterborne Zn toxicity. Moreover, Zn reduced significantly; meanwhile, RCP supplementation increased significantly superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities. Notably, Zn exposure could reduce fish growth and antioxidant activity and increase Zn deposition in whole fish body. And RCP intake could enhance the antioxidant activity exerting a protective effect against Zn toxicity, thereby reducing Zn bioaccumulation in whole fish body.     

Dietary butyric acid improved growth,digestive enzyme activities and humoral immune parameters in Barramundi (Lates calcarifer)

A six‐week feeding trial was conducted to determine the effect of butyric acid (BA) inclusion in diet on performance of Barramundi (Lates calcarifer). Fish (12.0 ± 0.2 g) were fed with four experimental diets contained 0.0 (control), 2.5, 5.0 and 10.0 g BA/kg in triplicate. Fish fed on 5 and 10 g BA/kg diets had higher growth and total alkaline protease and lipase activities than the other treatments. Fillet protein content in BA‐supplemented groups was higher than the control. Liver catalase activity was highest in 2.5 g BA/kg group compared with the other groups. The values of liver superoxide dismutase activity and serum total protein concentration in 5 and 10 g BA/kg treatments were higher than those in the control (p < .05). Moreover, the highest and the lowest levels of serum lysozyme activity were noticed in the 10 g BA/kg and the control groups, respectively (p < .05). Also, the highest respiratory burst activity was observed in fish fed 5 g BA/kg feed. Supplementing diet with 2.5 or 5 g BA/kg resulted in higher serum haemolytic activity in fish compared with the other groups. The number of red and white blood cells increased in fish fed BA‐supplemented diets compared with the control (p < .05). In conclusion, the results of this study showed inclusion of BA at 5 g/kg diet in L. calcarifer juveniles improved growth and upgraded the general health condition by enhancing fish antioxidant enzyme activities and haemato‐immunological responses.     

Effect of supplemental taurine on juvenile channel catfish Ictalurus punctatus growth performance

Juvenile channel catfish (5.6 g/fish) were fed a basal diet that contained major protein (soybean meal, cottonseed meal) and energy (ground corn grain, wheat middlings) ingredients that were derived from plant sources. The basal diet was supplemented with three levels of crystalline taurine to provide 1, 2 and 5 g/kg taurine. In addition, a fifth diet that contained 80 g/kg menhaden fishmeal formulated with the same plant‐source ingredients was included as the positive control diet. Fish were fed the five diets once daily for 12 weeks. Weight gain was highest in catfish fed taurine at 2 g/kg (47.8 g/fish) compared to catfish fed the control basal diet (40.8 g/fish) and 80 g/kg fishmeal diet (41.1 g/fish) (p < .05). Among the taurine‐supplemented diets, weight gain was lowest in catfish fed taurine at 5 g/kg. Feed conversion ratio (FCR) was significantly improved in fish fed diets supplemented with taurine at 2 g/kg compared to all other treatments (p < .01). Survival during the growth study ranged from 98.0 to 99.0% (p > .05) for all treatments. The results suggest taurine supplementation to juvenile channel catfish may improve weight gain and FCR.     

Nano zinc vis‐à‐vis inorganic Zinc as feed additives: Effects on growth,activity of hepatic enzymes and non‐specific immunity in rohu,Labeo rohita (Hamilton) fingerlings

The effects of dietary administration of inorganic zinc (zinc sulphate, ZnSO₄) and nano zinc (zinc oxide nanoparticles, ZnO‐NP) were evaluated in rohu, Labeo rohita fingerlings. Fish were fed with a basal diet (Control) supplemented with ZnSO₄ (T1, T2 and T3) and ZnO‐NP (T4, T5 and T6) at 10, 20 and 30 mg/kg, respectively, for a duration of 45 days. The results revealed that fish fed diet containing 20 mg ZnO‐NP per kg (T5) had the highest weight gain and specific growth rate (SGR, % per day), which was significantly different (p < .05) from the other experimental diets. Significantly (p < .05), higher activities of the digestive and metabolic enzymes were recorded in the fish fed ZnO‐NP containing diets as compared to the diets containing inorganic Zn or control diet. The maximum serum glucose and protein levels were noted in fish reared on diet T5. Both SGOT and SGPT activities were significantly increased in fish fed Zn‐supplemented diets (T1 to T6), as compared to the control group. Similarly, innate immune parameters were improved with feeding Zn incorporated diets. The highest phagocytic (40.74 ± 0.65%) and respiratory burst (0.33 ± 0.001, OD 630nm) activities were recorded in the fish fed diet containing ZnO‐NPs at 20 mg/kg (T5). The maximum superoxide production and serum peroxidase activity were detected in the fish fed T5 and T6 diets. Overall, results indicated that short‐duration feeding (≤45 days) of dietary ZnO‐NP (20 mg/kg) improved growth, enzyme activity, serum biochemical parameters and immune function in rohu fingerlings.     

Influence of dietary protein level on growth performance,digestibility and activity of immunity‐related enzymes of leopard coral grouper,Plectropomus leopardus (Lacépède, 1802)

An 8‐week feeding trial was conducted to assess the interaction between dietary protein levels and fish growth, digestibility and activity of immunity‐related enzymes of Plectropomus leopardus. Five diets with different protein levels (400 g/kg, 450 g/kg, 500 g/kg, 550 g/kg and 600 g/kg protein) were designed. P. leopardus fed with 500 g/kg, 550 g/kg and 600 g/kg dietary protein, showed higher weight gain rates than fish fed 400 g/kg and 450 g/kg dietary protein. Ingestion rate in fish fed with 500 g/kg dietary protein was significantly higher than those with other diets. P. leopardus fed with 500 g/kg, 550 g/kg and 600 g/kg dietary protein, showed that feed coefficients were significantly lower than those fed with 400 g/kg and 450 g/kg dietary protein. Net protein utilization was significantly lower in fish fed with 400 g/kg diet than those with other diets. Fish fed with 400 g/kg and 450 g/kg dietary protein had an apparent feed digestibility coefficient for dry matter that was significantly lower than that with other diets. Protease activity was highest in fish fed on 500 g/kg dietary protein. Fish fed with 500 g/kg dietary protein, had the highest superoxide dismutase activity. Fish fed with 600 g/kg dietary protein, had the highest alkaline phosphatase activity. Thus, a diet containing 500 g/kg protein is recommended for P. leopardus aquaculture.     

Dietary Vitamin C Requirement of Hybrid Striped Bass Morone chrysops♀× M. saxatilis ♂

A feeding trial was conducted to determine the dietary vitamin C requirement of juvenile hybrid striped bass Morone chrysops × M. saxatilis . Fish were fed a semi-purified basal diet with 40% crude protein and an energy to protein ratio of 8 kcal/g for a conditioning period of 2 wk. This diet which was not supplemented with vitamin C contained approximately 6-mg vitamin C/kg. Following conditioning, fish (approximately 0.55 g initial weight) were stocked as groups of 20 in 38-L aquaria and fed the basal diet and experimental diets supplemented with 10, 20, 30, 45, 60, 75, or 150-mg vitamin C/kg as ascorbate polyphosphate for a period of 10 wk. Fish fed the basal diet and the diet supplemented with 10-mg vitamin C/kg exhibited signs of vitamin C deficiency including suppressed weight gain, reduced plasma and liver ascorbic acid levels, and abnormalities in isthmus cartilage formation. Plasma and liver ascorbic acid levels generally reflected dietary supplementation with the lowest levels occurring in fish fed the basal diet and higher levels in fish fed the supplemented diets. The minimum dietary requirement (±SE) based on non-linear least squares regression analysis of weight gain was 22 (±6) mg vitamin C/kg diet.     

Effects of glutamate in low‐phosphorus diets on growth performance,antioxidant enzyme activity,immune‐related gene expression and resistance to Aeromonas hydrophila of juvenile mirror carp (Cyprinus carpio)

This study investigated the effects of glutamate (Glu) in low‐phosphorus diets on growth performance, haematological indices, antioxidant enzyme activity, immune‐related gene expression and resistance to Aeromonas hydrophila in juvenile mirror carp (Cyprinus carpio) (5.07 ± 0.02 g). Fish were fed either graded levels of Glu (0 g/kg, 5 g/kg,  10 g/kg and 20 g/kg, named G0, G0.5, G1 and G2, respectively) in a low‐phosphorus diet (15 g/kg NaH₂PO_4, 0.49), or a normal phosphorus diet ( 20 g/kg NaH₂PO_4, 0.61) without added Glu (C), for 8 weeks. At the end of the feeding trial, the fish were challenged with A. hydrophila. Compared with G0 group, 10 g/kg and 20 g/kg Glu supplementation of the low‐phosphorus diet significantly improved the final weight, WGR, SGR and PER, and decreased FCR (p < .05). Glu supplementation of the low‐phosphorus diet significantly enhanced the T‐AOC, SOD activity and GSH content in intestine (p < .05). Glu supplementation significantly reduced MDA content in foregut and midgut and increased CAT activity in midgut and hindgut (p < .05). Regarding immune‐related gene expression, Glu supplementation significantly diminished the up‐regulation of intestinal TNF‐α, IL‐1β and IL‐8 mRNA levels induced by phosphorus deficiency (p < .05). The survival rate of the G1 group was significantly higher than that of the G0 group (p < .05). In conclusion, 10 g/kg Glu supplementation in low‐phosphorus diets can improve the growth performance, enhance the activity of intestinal antioxidant enzymes and strengthen the immune function of juvenile mirror carp.     

Dietary vitamin E requirement of sub‐adult genetically improved farmed tilapia strain of Nile tilapia (Oreochromis niloticus) reared in freshwater

A two‐factor orthogonal test was conducted to determine the dietary vitamin E (VE, dl ‐α‐tocopheryl acetate) requirement for sub‐adult GIFT strain of Nile tilapia (Oreochromis niloticus) at two lipid levels, and evaluate its effect on antioxidant responses. A basal diet containing 60 or 130 g/kg of soybean oil was supplemented with 0, 20, 40, 60, 120 and 240 mg VE/kg, respectively. Each diet was fed to three replicate groups of tilapia with initial weight (80.3 ± 0.7) g for 10 weeks. Results showed that the weight gain, feed efficiency and hepatic VE retention of fish were significantly increased by the increased VE in diets. In groups with 60 and 130 g/kg lipid, fish fed diets supplemented with VE had higher serum superoxide dismutase (SOD) and catalase activity, and lower malondialdehyde content than fish fed the VE un‐supplemented diet (p < .05). The proximate composition of fish had no significant difference in the group with 130 g/kg lipid, whereas crude lipid and ash content were significantly affected by dietary VE in the group with 60 g/kg lipid. Based on broken‐line regression analysis, dietary VE requirement to support the maximum weight gain and serum SOD were 43.2–45.8 and 66.0–76.1 mg/kg in diets with 60 and 130 g/kg lipid, respectively.     

Effects of inorganic and organic dietary copper supplementation on growth performance and tissue composition for juvenile red drum (Sciaenops ocellatus L.)

A feeding trial was conducted to evaluate the dietary copper requirement of red drum (Sciaenops ocellatus) and compare the bioavailability of copper sulphate (CuSO₄) and copper‐ethanolamine. A basal diet was formulated using semi‐purified ingredients and analysed to contain 3 mg Cu/kg. Both copper sources were supplemented to the basal diet at either 5, 10 or 20 mg Cu/kg of dry diet. No significant differences were observed in growth performance of fish fed the various diets. However, red drum fed all copper‐supplemented diets retained more copper in liver and whole‐body tissues compared to fish fed the basal diet. Within both inorganic and organic copper treatments, the highest tissue copper concentrations were observed in fish fed diets supplemented with 10 mg Cu/kg. No significant differences were detected in net copper retention regardless of the nature of the copper source; hence, the bioavailability of copper sulphate and copper‐ethanolamine complex was not different in the diets for juvenile red drum. Furthermore, the minimum copper requirement for growth performance of juvenile red drum appeared to be satisfied when fish were fed the basal diet containing 3 mg Cu/kg diet, and no detrimental effects were observed in red drum fed diets supplemented with 20 mg Cu/kg.     

Effects of Dietary Geniposide on Growth,Flesh Quality,and Lipid Metabolism of Grass Carp,Ctenopharyngodon idella

The aim of this study was to investigate effects of dietary geniposide (GP) on growth performance, flesh quality, and lipid metabolism of grass carp, Ctenopharyngodon idella (95.2 ± 0.6 g), fed seven different diets, including a control diet; Eucommia ulmoides (EU)–supplemented diet (20 g/kg); and GP‐supplemented diets containing 100, 200, 400, 600, and 800 mg/kg GP, respectively. Weight gain rate was significantly improved (P < 0.05) and feed conversation ratio was significantly decreased (P < 0.05) by supplementation of EU. Grass carp fed 100–800 mg/kg GP‐supplemented diets showed significantly higher total collagen and alkaline‐insoluble collagen content in muscle than control (P < 0.05). Contents of total collagen and the alkaline‐insoluble collagen content in the skin of grass carp were significantly increased by dietary 600–800 mg/kg GP and EU (P < 0.05). Fish fed diets containing 600–800 mg/kg GP showed significantly lower muscle crude lipid content than the EU, control, and 100–400 mg/kg GP groups (P < 0.05). Fish fed 400–800 mg/kg GP diets had significantly higher muscle fiber density and lower muscle fiber diameter and serum triglyceride level than the control (P < 0.05). In conclusion, supplementation of GP could improve flesh quality, but not growth of grass carp. The supplemental level of GP for improving flesh quality was estimated to be a 400–600 mg/kg diet.