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.     

Effects of dietary coated protease on growth performance,feed utilization,nutrient apparent digestibility,intestinal and hepatopancreas structure in juvenile Gibel carp (Carassius auratus gibelio)

This study was conducted to investigate the effects of dietary protease on growth performance, feed utilization, whole‐body proximate composition, nutrient digestibility, intestinal and hepatopancreas structure of juvenile Gibel carp, Carassius auratus gibelio (mean weight 8.08 ± 0.18 g). Six diets were prepared, including a positive control diet (dietary protein 350 g/kg, PC), one negative control diet (dietary protein 33 g/kg, NC) and four protease supplementations diets, which were 75, 150, 300 and 600 mg/kg protease NC diet. After 12 weeks of diet feeding in indoor recycle aquarium tanks, no significant difference (p > .05) was found on growth performance between fish fed diet with 75–600 mg/kg protease and the PC group. Compared with the fish fed the NC diet, the specific growth rate of fish fed 300 mg/kg protease increased significantly (p < .05), as well as protein efficiency ratios (p < .05), while feed conversion was the opposite (p < .05). The nutrient digestibility of crude protein and lipid was higher (p < .05) in fish fed 150 mg/kg protease diet than the PC diet. Whole‐body proximate composition of fish was not affected (p > .05) by the dietary treatment. Serum alkaline phosphatase and albumin were significantly affected by dietary protease (p < .05), while the content of total protein, glucose, triglyceride, total cholesterol, aspartate aminotransferase and alanine aminotransferase activities in serum was not affected (p > .05). Foregut muscular thickness was thinner (p < .05), when the fish fed diets supplementation of protease in 150 or 600 mg/kg diet than the NC diet. Protease activities in hepatopancreas and foregut were higher (p < .05), in the fish fed 150 or 300 mg/kg protease diet than the fish fed the PC diet, but those in the mid‐ and hindgut were not significantly affected (p > .05) by the dietary treatments. Based on the regression analysis of weight gain rate, the optimal dietary inclusion level of protease was 400 mg/kg in the diet for juvenile Carassius auratus gibelio.     

Effects of dietary geniposidic acid on growth performance,flesh quality and collagen gene expression of grass carp,Ctenopharyngodon idella

This study was conducted to investigate the effects of dietary geniposidic acid (GA) on growth performance, flesh quality and collagen gene expression of grass carp (Ctenopharyngodon idella). The fish with an initial body weight of 47.1 ± 0.8 g were fed one of the seven diets, including control diet, Eucommia ulmoides (EU)‐supplemented diet (20 g/kg) and GA‐supplemented diets (200, 400, 600, 800 and 1,000 mg/kg GA) for 75 days. The growth performance and muscle proximate composition showed no difference among groups (p > .05). Dietary GA (200–1,000 mg/kg) increased the contents of total collagen and alkaline‐insoluble collagen in skin (p < .05), and high supplementation of GA (600–1,000 mg/kg GA) and EU increased the contents of total collagen, alkaline‐insoluble collagen and total amino acids (p < .05), but reduced the lipid level in muscle (p < .05). In collagen gene expression, EU and 200–1,000 mg/kg GA increased COL1A1 expression in muscle and skin (p < .05), but the expression of COL1A2 was increased only by high supplementation of GA (1,000 mg/kg, or 800–1,000 mg/kg) (p < .05). In conclusion, dietary GA improved the flesh quality of grass carp, and the supplementation level was estimated to be 600 mg/kg diet.     

Effects of fishmeal replacement with cottonseed meal protein hydrolysate on growth,digestion and intestinal histology of juvenile Chinese soft‐shelled turtle,Pelodiscus sinensis

A 60‐day feeding experiment was conducted to evaluate the effects of fishmeal (FM) replacement with cottonseed meal protein hydrolysate (CPH) on growth, digestion and intestinal histology of juvenile Chinese soft‐shelled turtle (Pelodiscus sinensis). Five diets were formulated to replace 0, 50, 100, and 150 g/kg fishmeal protein by CPH (CPH0, CPH5, CPH10, CPH15) and CPH15L (CPH15 with micro capsule‐L‐lysine). Weight gain, feed conversion rate and protein efficiency ratio showed no significant differences compared to control group (p > .05). The highest feed intake indicated in CPH15 (p < .05). The composition of whole‐body varied slightly in each groups (p > .05). The trypsin activity significantly elevated when dietary fishmeal protein was replaced by CPH at 30–90 g/kg (p < .05). A significantly higher lipase activities in CPH5 than control group (p < .05). The CPH5‐10 groups showed higher villus height than the other groups (p < .05). The microvillus length in turtles with CPH showed a significant increasing length (p < .05). The results indicated that replacing up to 90 g/kg of dietary fishmeal protein with CPH did not hamper growth or reduce feed intake of turtles. Moreover, CPH replaced 60 g/kg FMP can increase intestine digestive enzymes activities and improve intestinal development.     

Effects of antimicrobial peptides on growth,morphology of foregut villi and related genes mRNA expression in the common carp (Cyprinus carpio)

A 60‐day feeding trial was conducted to examine the effects of different levels (0, 100, 200, 400 and 600 mg/kg) of antimicrobial peptides on growth, protease activity of foregut, the morphology of foregut villi and related genes mRNA expression level in the common carp (Cyprinus carpio). The results showed that the feed of antimicrobial peptides promote common carp growth, and the optimal dosage of antimicrobial peptides is 200–333 mg/kg in the common carp feed. The protease activity of 200 and 400 mg/kg groups were significantly higher than the control and other groups (p < 0.05). The foregut villus height with 100, 200 and 400 mg/kg antimicrobial peptide groups were significantly higher than control group (p < 0.05). The crypt depth of 200 and 400 mg/kg antimicrobial peptide groups were significantly lower than control group (p < 0.05). The ratio of villus height and crypt depth of 100, 200 and 400 mg/kg antimicrobial peptide groups were significantly higher than control group (p < 0.05). The ratio with 600 mg/kg group was significantly lower than the control group (p < 0.05). The IGF‐I gene expression level of 200 mg/kg and 400 mg/kg groups were significantly higher than the control group and 600 mg/kg group (p < 0.05). The IL‐1β gene expression level of 100 mg/kg and 200 mg/kg groups were significantly higher than the control group (p < 0.05). These results indicated up‐regulation of growth and immune related genes in antimicrobial peptides fed common carp. Correlation analysis showed that IGF‐I mRNA and IL‐1β mRNA were positively correlated with SGR. IL‐1β mRNA and FCR were significantly negative correlated. It indicated that growth and immune gene common regulated the growth of the carp under antimicrobial peptides intervention. In conclusion, antimicrobial peptides can improve growth and related genes mRNA expression in the common carp. Further studies using molecular biological technique or immunologic methods are required to conclude that antimicrobial peptides are beneficial in common carp.     

Effects of α‐ketoglutarate on growth performance,antioxidant capacity and ammonia metabolization against chronic carbonate alkalinity stress in Songpu mirror carp (Cyprinus carpio Songpu)

A 3 × 2 factorial experiment was conducted to investigate the interaction between carbonate alkalinity and dietary α‐ketoglutarate (AKG) levels on the growth performance, antioxidant capacity and ammonia metabolization of Songpu mirror carp (Cyprinus carpio Songpu). Each diet (0%, 1% AKG) was randomly allotted to 0 mmol/L, 15 mmol/L, 30 mmol/L carbonate alkalinity groups with three replicate aquaria. The weight gain rate (WGR) significantly increased in the 1% AKG group and significantly decreased with increasing carbonate alkalinity (p < .05). Crude ash was significantly affected by the interaction between carbonate alkalinity and dietary AKG levels and significantly increased in the 1% AKG group (p < .05). A significant interaction between carbonate alkalinity and dietary AKG levels on superoxide dismutase (SOD) activities in hepatopancreas was observed (p < .05). The increasing carbonate alkalinities significantly decreased SOD activities in the hepatopancreas and foregut, catalase (CAT) activities in the hepatopancreas, foregut, midgut and hindgut and glutathione (GSH) contents in the hepatopancreas and foregut (p < .05). Despite AKG addition, the blood ammonia content still increased with increasing carbonate alkalinities. The gene expressions of AQP3, Rhag, Rhcg2 and Na⁺/K⁺‐ATPase (NKA) in the gills and glutamine synthase (GS) in the brain were significantly upregulated with increasing carbonate alkalinities (p < .05). In the 1% AKG group, GS gene expression significantly upregulated in the brains, whereas AQP3, Rhag, Rhcg2 and NKA gene expressions significantly downregulated in the gills (p < .05). In summary, the 1% AKG addition can enhance the gene expression of ammonia metabolization and improve the antioxidant capacity of Songpu mirror carp with chronic carbonate alkalinity stress.     

Lipid deposition patterns among different sizes of three commercial fish species

This study was conducted to compare lipid deposition pattern of three fish species among fish size, Large yellow croaker (Larmichthys crocea), Japanese seabass (Lateolabrax japonicus) and Turbot (Scophthalmus maximus L.), Using magnetic resonance imaging technology for adult fish, results showed that lipid of large yellow croaker mainly deposits in abdominal cavity wall, while for Japanese seabass mainly deposit in visceral adipose tissue and for turbot lipid mainly distribute subcutaneous tissue. Three sizes for each species were selected: S1 (small size), S2 (intermediate size) and S3 (big size), to examine chemical analysis. Results of chemical analysis indicated that whole body lipid content of large yellow croaker significantly increased with the increase in body weight, but Japanese seabass and turbot significantly decreased (p < .05). Lipid content of muscle and intestinal tract in large yellow croaker significantly increased with the increase in body weight (p < .05), but lipid content of adipose tissue, kidney, heart and skin in S2 group were higher than S1 and S3 groups (p < .05). Lipid content of liver, eye, kidney and brain in Japanese seabass significantly increased with the increase in body weight (p < .05), but lipid content of stomach and heart showed an opposite trend. Lipid content of liver, adipose tissue, skin and eye in turbot significantly decreased (p < .05), but lipid content of brain significantly increased with the increase in body weight (p < .05). The results indicated that lipid content of different tissues in fish presented different trends, which was species‐dependent.     

Ferulic acid: A natural compound as an efficient feed additive for GIFT (Oreochromis niloticus)

This study aimed to investigate the effect of dietary ferulic acid (FA) supplementation on growth performance, antioxidant capacity and some physical characteristics of flesh in genetic improvement of farmed tilapia (GIFT) juveniles. Five diets supplemented with 0, 50, 100, 200 and 400 mg/kg FA were prepared. Weight gain was significantly increased, while feed conversion ratio, viscerosomatic index and hepatosomatic index were significantly decreased in fish fed FA diet at 100 mg/kg feed (p < .05). FA supplementation improved hepatic and serum superoxide dismutase and catalase activities, but decreased the malondialdehyde content (p < .05). Furthermore, with the addition of FA, serum triacylglycerol, cholesterol, low‐density lipoprotein cholesterol contents, alanine aminotransferase and aspartate transaminase activities were reduced, whereas serum high‐density lipoprotein cholesterol content, alkaline phosphatase and lysozyme activities were enhanced. The texture profile analysis parameters and water‐holding capacity tended to increase while cooking loss was decreased by dietary FA supplementation (p < .05). These results suggested that dietary FA supplementation increased the growth performance and antioxidant capacity of GIFT, and improved some physical characteristics of flesh and serum biochemical parameters. The optimum dietary FA level was 100 mg/kg in diet.     

Replacing fish meal with vegetable protein sources in feed for juvenile red swamp crayfish,Procambarus clarkii: Effects of amino acids supplementation on growth and feed utilization

An 8‐week growth trial was conducted to investigate the effects of dietary fish meal replacement with a vegetable mixture of soybean meal and rapeseed meal (1:1) on growth of juvenile red swamp crayfish. Nine isonitrogenous diets were designed: V0, V34, V50, V65, V73 and V81 with six levels of vegetable proteins, and VA48, VA63 and VA78 by further adding crystalline lysine and methionine into V50, V65 and V81. Compared with V0, V34 significantly improved the specific growth rate (SGR), while V65, V73, V81 and VA78 depressed the SGR (p < .05). Feeding rate showed a decreasing trend as dietary vegetable protein level increased (p < .05), except that in VA48 group. Significantly lower FCR and higher PER were observed in V34 group, whereas all vegetable protein diets depressed the feed utilization of crayfish (p < .05). Crayfish fed with diets containing vegetable proteins showed significantly lower hepatosomatic indices and higher condition factors than the control (p < .05). Muscle lipid content was significantly (p < .05) lowered in V81 group, but not in VA78 group. The results suggested that 338 g/kg vegetable protein improved growth performance of crayfish. Excessive vegetable protein depressed the growth of crayfish, which could be prevented by lysine and methionine supplementation except for the all vegetable protein diets.     

Effects of totally replacing dietary fish oil by linseed oil or soybean oil on juvenile hybrid sturgeon,Acipenser baeri Brandt♀×A. schrenckii Brandt♂

The growth performance, body composition, fillet fatty acid content, serum hepatic enzymes and postprandial changes in serum lipid metabolism of hybrid sturgeon (70.8 ± 0.5 g) were investigated to determine the effects of total replacement of 80 g kg^‐1 fish oil (diet A) with linseed oil (diet B) and soybean oil (diet C), respectively. No significant differences in weight gain rate and specific growth ratio were observed among all fish groups (p > .05). Diet A fish group had the highest, but diet B fish group had the lowest feed intake (p < .05). Feed efficiency of fish fed diet A was significantly lower than the other two fish groups (p < .05). Fish fed diet A had the lowest fillet and liver lipid contents (p < .05). Serum lactate dehydrogenase, alanine aminotransferase and aspartate aminotransferase activities of fish fed diet A were significantly lower than those of fish fed diets B and C (p < .05). The contents of linoleic acid (C18:2n6) and linolenic acid (C18:3n3) in fillets showed a significantly positive linear correlation with the diets. Serum glucose and non‐esterified fatty acid were just affected by the time point (p < .05). The lipid source, time point and interaction of both factors had significant effects on serum triglyceride, high‐density lipoprotein cholesterol and low‐density lipoprotein cholesterol (p < .05). Serum total cholesterol was only affected by interaction of time point and lipid source (p < .05), and ketone body was not affected by lipid source, time point or interaction of both factors (p > .05). In summary, total replacement of fish oil with linseed oil or soybean oil had no significant adverse effects on hybrid sturgeon growth during 84‐day period, and linoleic acid and linolenic acid in fillet were modified by dietary treatments.     

Effects of Chinese herbal medicines mixture on growth performance digestive enzyme activity immune response of juvenile Japanese seabass,Lateolabrax japonicus

A single factorial experiment was conducted to investigate the effects of Chinese herbal medicines mixture (CHMM) on growth performance, digestive enzyme activity and immune response of Japanese seabass, Lateolabrax japonicus (initial weight 5.01 ± 0.32 g). The fish were fed diets containing six levels of CHMM (0, 4, 8, 12, 16 and 20 g/kg) for 4 weeks. The results showed that the weight gain rate and specific growth rate (SGR) enhanced significantly in fish fed diet containing 8 g/kg CHMM (p < .05), while the feed conversion ratio (FCR) in the 4 and 8 g/kg CHMM groups reduced significantly compared with the control (p < .05). The body crude protein levels in 8 and 16 g/kg groups were significantly higher than the control (p < .05). The pepsin, amylase and lipase activities elevated significantly in the stomach of fish fed 8 g/kg CHMM, while the erepsin and lipase in the intestine of fish in 12 and 16 g/kg groups were higher significantly than the control (p < .05). The lysozyme, alkaline phosphatase, acid phosphatase (ACP), total antioxidative capacity activities in serum of fish fed 12 g/kg CHMM were higher significantly than those in the control (p < .05), while the total superoxide dismutase (SOD), total antioxidative capacity, catalase, alkaline phosphatase (AKP) and ACP activities in hepatopancreas of fish in 12 g/kg group were all significantly higher than those in the control (p < .05). Regression analysis showed that the relationships between dietary CHMM levels and either FCR, SGR, erepsin, pepsin or lysozyme activities were best expressed by quadratic or cubic regression equations, and the optimal inclusion levels are 11.4, 10.7, 10.7, 8.4 and 10.5 g/kg for maximum FCR, SGR, erepsin, pepsin and lysozyme activities, respectively. Under the present experimental condition, the optimal supplementary level of CHMM in the diet of Japanese seabass is 8–12 g/kg.     

Effect of the C/N ratio on inorganic nitrogen control and the growth and physiological parameters of tilapias fingerlings,Oreochromis niloticu reared in biofloc systems

The objective of this study was to document the effects of different C/N ratios on inorganic nitrogen control and the growth and health of tilapia (Oreochromis niloticus) fingerlings reared in biofloc systems. The fish (0.50 ± 0.02 g) were randomly assigned to the control group (clear water) or to one of three biofloc groups (added glucose) with a C/N ratio of 10, 15, or 20 (CN‐10, CN‐15, or CN‐20, respectively). All four groups were cultured for 120 days. The inorganic nitrogen dynamics showed that heterotrophic and autotrophic bacteria existed in the low C/N ratio group, and heterotrophic bacteria dominated the high C/N ratio group. In addition, growth was significantly better in the CN‐10 and CN‐15 groups (15.67 ± 0.78 g and 14.75 ± 0.54 g, respectively) compared to the CN‐20 (13.04 ± 0.94 g) and control (13.04 ± 0.46 g) groups (p < .05). Activities of the digestive enzymes lipase and trypsin were significantly higher in the CN‐10 and CN‐15 groups than in the control group (p < .05). In addition, activities of lysozyme, alkaline phosphatase, superoxide dismutase, glutathione and malondialdehyde were significantly higher in the CN‐10 and CN‐15 groups than in the control group (p < .05). Finally, the concentrations of glucose and cortisol in the biofloc systems were significantly lower than those in the control group (p < .05). However, the concentrations of triglyceride, aspartate transaminase and alanine aminotransferase did not differ significantly among the four groups (p > .05). At the end of the trial, an acute crowding and hypoxia stress test performed for 3 days showed that the CN‐10 and CN‐15 groups had the best survival.     

Dietary nucleotide mixture effects on reproductive and performance,ovary fatty acid profile and biochemical parameters of female Pacific shrimp Litopenaeus vannamei

The effects of different dietary nucleotide mixture (NT) levels (0, 2, 4 and 6 g/kg) were investigated on the reproductive performance, fatty acid profile and biochemical parameters in Litopenaeus vannamei female that were co‐fed with fresh food (two times daily) and experimental diets (two times daily) for 30 days. Sampling was carried out at the first day of the trial, before eyestalk ablation (ESA) (day 21) and after ESA (day 30). Reproductive performance parameters including the hepatopancreatic index, absolute fecundity, egg diameter and latency period were higher in the NT‐supplemented groups than the control group (p < .05). Total n‐3 polyunsaturated fatty acids in the ovaries, especially eicosapentaenoic acid, were higher in the NT‐supplemented groups than in the control (222.6 ± 7.3 versus 204.7 ± 3.0 mg/g extracted lipid) (p < .05). Total hemocyte count, granular cells, plasma glucose (Glu), total protein (TP), calcium (Ca²⁺), total cholesterol (Chol), triglyceride (Tg) and high‐density lipoprotein (HDL) levels were significantly increased in the NT‐supplemented groups in comparison with the control group (p < .05). After ESA, the concentration of plasma Glu, TP, Chol and Tg significantly decreased, but HDL levels increased in all groups (p < .05). These results suggested that the application of dietary NT may present a novel strategy for increasing reproductive performance and health status in L. vannamei.     

Ontogenic changes in the digestive enzyme activities and the effect of different starvation duration on the digestive enzyme activities of larval red swamp crayfish (Procambarus clarkii)

This study was performed to determine the effect of starvation and delayed feeding on activities of digestive enzymes and alkaline phosphatase (ALP) of larval red swamp crayfish (Procambarus clarkii), so as to reveal the tolerance to prolonged starvation and the recovery of digestive enzymes after delayed feeding in larval and juvenile P. clarkii. In the control group, activities of trypsin and ALP increased significantly (p < .05) with day‐age and then kept constant at 24 days after hatching (DAH) and 10 DAH, respectively, whereas the activities of amylase and pepsin increased firstly then decreased with day‐age, and the activity of lipase increased firstly then decreased and then increased again during the development period of juvenile P. clarkii (1–31 DAH). In the group with continuous starvation (CS), activities of pepsin and lipase both decreased (p < .05) after fasting, and the activities of pepsin, lipase and trypsin in the groups with delayed feeding all increased (p < .05) and recover to the levels of the control group after food supply. However, the activity of amylase increased (p < .05) in the CS group, and it decreased to normal level after food supply. The ALP activity did not significantly (p > .05) vary after starvation, whereas it decreased in the groups with delayed feeding after 1 day of food supply, and then increased back to the level similar with the control group. Results from this study could provide information for diet preparation and feeding regime in larval and juvenile red swamp crayfish culture.     

Evaluation of growth,feed utilization efficiency and immune parameters in tiger shrimp (Penaeus monodon) fed diets supplemented with or diet fermented with gut bacterium Bacillus sp. DDKRC1. isolated from gut of Asian seabass (Lates calcarifer)

An experiment was conducted to assess the effect of supplementation of cellulolytic gut bacterium with plant protein‐based diet on growth, digestibility and digestive enzyme status of tiger shrimp, Penaeus monodon. Bacillus sp. DDKRC1. (JN641289), a potential cellulolytic bacterium, isolated from the gut of Asian seabass was used as feed supplement in this experiment. The shrimps of group I, II and III were fed with control diet (without bacterial supplement, D1), diet supplemented with live Bacillus sp. DDKRC1. at 2.94 × 10⁷ cfu per 100 g feed (D2) and diet fermented (48 hr) with same bacteria (D3) respectively. At the end of the 42 days experiment, shrimps of group II showed significantly better (p < .01) growth and protein efficiency ratio (PER) and lower (p < .01) feed conversion ratio (FCR) as compared to group I and III. Dry matter, cellulose, hemicellulose and lipid digestibilities were significantly (p < .01) higher in group II than other two groups. Cellulase, amylase and protease activities in the gastrointestinal (GI) tract were significantly (p < .01) higher in group II as compared to other two groups. Total heterotrophic count, amylolytic, cellulolytic and proteolytic bacterial counts in gut were significantly (p < .01) higher in group II as compared to other two groups. Haematological analysis indicated better (p < .05) immune response in groups II and III than control group. Diets D2 and D3 showed better effect on growth, digestibility, FCR, survival and immune response of P. monodon as compared to D1.     

Effects of different levels of dietary protein on the growth performance,nutrient utilization,digestive enzymes and physiological status of white shrimp,Litopenaeus vannamei juveniles reared in inland saline water

A 60‐day feeding trial was conducted to illustrate the effect of dietary protein levels on the growth and physio‐metabolic responses of juvenile Litopenaeus vannamei reared in inland saline water (ISW). Six isoenergetic (15 MJ/kg) and isolipidic (60 g/kg) diets with graded level of crude protein viz., 240 (T240), 260 (T260), 280 (T280), 300 (T300), 320 (T320) and 340 (T340) g/kg diet were formulated. Significantly higher (p < .05) weight gain (%), specific growth rate, with lower food conversion ratio were found in T320 and T340 groups. The protein utilizing efficiency and whole‐body protein content were significantly higher (p < .05) in the T320 group. Trypsin activity increased with the increasing dietary CP level but amylase activity decreased with the increasing dietary CP level. Transaminase enzymes, haemolymph protein and haemocyanin were elevated in T320 and T340 groups. The lactate dehydrogenase and malate dehydrogenase activities were significantly higher (p < .05) in the T240 group. Shrimp of T240 group had the lowest (p < .05) glycogen and total haemocyte count with highest (p < .05) haemolymph glucose and antioxidant enzymes activities than the other groups. Based on the results, feeding 320 g CP/kg is found to be optimum for supporting maximum growth and health status of L. vannamei reared in ISW at 8 g/L salinity. The finding of the present study will help in developing a low‐cost feed for L. vannamei reared in ISW.     

Assessment of induction and recovery times of anaesthesia in Astyanax bimaculatus using 2‐phenoxyethanol and the essential oils of Melaleuca alternifolia and Ocimum gratissimum

This study aimed to determine the lowest effective concentration (LEC) of 2‐phenoxyethanol (2‐Phe) and essential oils (EOs) of Melaleuca alternifolia and Ocimum gratissimum able to induce anaesthesia in Astyanax bimaculatus. LEC was assumed to be the required concentration to carry out anaesthesia in less than 3 min with recovery in <5 min and sufficient to carry out routine aquaculture procedures. The following concentrations were tested: 2‐Phe (100, 200, 300, 400, 500 and 600 µl/L); M. alternifolia (200, 300, 400, 500 and 600 µl/L); and O. gratissimum (10, 20, 30, 40, 50, 60, 70, 100, 150, 250 and 300 µl/L). Results show that all three agents evaluated have effective anaesthetic properties for use in Astyanax bimaculatus with LEC for 2‐Phe, M. alternifolia and O. gratissimum of 200, 300 and 60 µl/L respectively.     

Enhancement of reproductive performance in shrimp Litopenaeus vannamei (Boone, 1931) by supplementation of Ulva clathrata meal in maturation diet in two commercial hatcheries

The effect of supplementing dehydrated seaweed Ulva clathrata (20 g/kg) in the squid fraction of a formulated fresh diet on the reproductive performance of Litopenaeus vannamei broodstock was evaluated in two commercial hatcheries (A and B). The origin of broodstock, use of ablation on females, tank/culture conditions (for maturation, spawning, and larval rearing) were different between hatcheries. Daily mortality was higher (p < .01) for females in the control group compared to Ulva‐fed group of hatchery A, where females were ablated. No differences in mortality were found for unablated females in hatchery B, or with males from either hatchery. In hatchery A, broodstock fed Ulva produced more eggs (an increase in +5% compared to control, p < .05) and nauplii per female (+18%, p < .01). In hatchery B, broodstock fed Ulva produced significantly more eggs (+26%, p < .05) and nauplii per day (+33%, p < .05). In hatcheries A and B, eggs from broodstock fed Ulva had increased hatching rates (+13 and +7%, respectively, p < .001 in both cases). The number of spawns per day had a tendency to be higher in broodstock fed Ulva in both hatcheries, but the difference did not reach statistical significance (+14% for hatchery A and +20% for hatchery B). Dehydrated U. clathrata appears therefore as a functional additive in L. vannamei maturation diets that enhances the reproductive performance at commercial scale, regardless of the management conditions.     

Effects of dietary copper nanoparticles and vitamin C supplementations on growth performance,immune response and stress resistance of red sea bream,Pagrus major

A 60‐day feeding trial was conducted to determine the effects of copper nanoparticles (Cu‐NPs) and vitamin C (VC) on red sea bream. Besides the control diet (D1), six diets were supplemented with Cu‐NPs and VC [0/800 (D2), 0/1,000 (D3), 0/1,200 (D4), 2/800 (D5), 2/1,000 (D6) and 2/1,200 (D7) mg Cu‐NPs/VC per kg]. Cu‐NP was a significant factor on final weight (FBW), weight gain (WG) and specific growth rate (SGR), feed intake (FI), feed (FER) and protein efficiency ratios (PER), protein gain (PG) and protein retention (PR), body protein and lipid contents, protease (PA) and bactericidal activities (BA) and tolerance against stress (LT50%) (p < .05). In addition, BA and LT50% were significantly affected by either Cu‐NPs or VC (p < .05). Fish fed Cu‐NPs or/and VC‐supplemented diets showed higher FBW, WG, SGR, PG, PR, FI, PA, LA and BA values when compared with the control group (p < .05). FER, PER and body lipid content were significantly enhanced in D4, D5, D6 and D7 groups; meanwhile, body protein and LT50% were significantly enhanced in D5, D6 and D7 groups when compared with D1 group (p < .05). In conclusion, dietary Cu‐NPs or/and VC improved growth and health of red sea bream.     

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.