Dietary trans‐cinnamic acid application for rainbow trout (Oncorhynchus mykiss): II. Effect on antioxidant status,digestive enzyme,blood biochemistry and liver antioxidant gene expression responses

The present study investigated the effects of dietary trans‐cinnamic acid (TrCin) on growth performance, biochemical composition, fatty acid composition, blood biochemistry, antioxidant status, digestive enzyme and liver antioxidant gene (EF1α, SOD1, SOD2, CAT, GPX1, GPX4, GR and GST) expression responses of rainbow trout, Oncorhynchus mykiss. Five experimental groups of fish with mean weights of 17.49 ± 0.08 g were used in the study; four of them were fed with TrCin‐supplemented diets (0.25 g/kg TrCin25, 0.50 g/kg TrCin50, 0.75 g/kg TrCin75 and 1.50 g/kg TrCin150), whereas an additive‐free basal diet served as the control (Cntr). At the end of the 60‐day feeding trial, the growth performance, biochemical composition and fatty acid composition were similar for all experimental groups. A decrease was observed in intestinal and stomach pH, serum triglyceride and AST, ALT, LDH and ALP levels in fish fed with especially 0.50 g/kg TrCin‐supplemented diet. Moreover, dietary TrCin especially at 0.50 g/kg incorporation level significantly increased the serum SOD and liver SOD2, CAT, GST, GPX1, GPX4 and GR gene expression responses. As a conclusion, feeding rainbow trout for a period of 60 days with a diet containing 0.50 g/kg TrCin might be sufficiently enough to improve the levels of antioxidant enzymes and health status in fish.     

Influence of nanochitosan/zeolite composite on growth performance,digestive enzymes and serum biochemical parameters in rainbow trout (Oncorhynchus mykiss)

Protective effects of nanochitosan/zeolite composite besides zeolite and chitosan/zeolite composite on rainbow trout growth, digestive enzyme activities and biochemical parameters were studied. Nanochitosan/zeolite hybrid composites with three different ratio of nanochitosan:zeolite (35:100, 3.5:100 and 0.35:100) were synthesized and analysed by X‐ray powder diffraction (XRD), thermal gravim (TG) analysis and scanning electron microscope (SEM) methods. Prepared composites as well as zeolite and control diets were fed to rainbow trout (50 g) for a period of 60 days. The addition of treated diets significantly improved growth performance compared to the control diet. Supplemental zeolite could only enhance the amylase activity in fish intestine, whereas other treatment groups could increase the pepsin activity besides intestinal alkaline phosphatase, trypsin and amylase activities. No differences were observed for intestinal acid phosphatase and lipase activities among the experimental diets. Meanwhile, serum total antioxidant activity and lipid peroxidation product, indicated by malondialdehyde (MDA), significantly increased and decreased, respectively, with some doses of administration, indicating the elevated antioxidant status in treatment groups. Serum‐specific marker enzymes, namely aspartate aminotransferase (AST) and alkaline phosphatase (ALP), were not affected in all groups. Meanwhile serum total protein in most treatment groups was significantly higher than the control group. Results showed that synthesized composites especially nanochitosan/zeolite composite at 5 g/kg had potential to enhance growth performance, digestive enzyme activities and some biochemical parameters in rainbow trout.     

Relationships between growth and disease resistance in rainbow trout,Oncorhynchus mykiss (Walbaum)

Rainbow trout from 23 families were evaluated for growth and resistance to the bacterial coldwater disease (BCWD) caused by Flavobacterium psychrophilum and infectious haematopoietic necrosis (IHN) caused by IHN virus. Average family weights were between 161 and 263 g with an average of 225 g at 213 days post‐fertilization with specific growth rates ranging from 2.37 to 2.88. Per cent survival of fish challenged with F. psychrophilum was between 18% and 100%, while for those challenged with IHNV, the range was between 12% and 93%. Significant positive correlations were found for end body weight and resistance to IHN (P < 0.05) and for early body weight and resistance to BCWD (P < 0.1). However, no significant correlations were detected between resistance to both pathogens or disease resistance and overall genetic diversity or diversity within the major histocompatibility locus.     

Dietary modulation of digestive enzymes by the administration of feed additives to rainbow trout,Oncorhynchus mykiss Walbaum

The aim of this study was to assess the metabolic and digestive enzyme activities in rainbow trout, Oncorhynchus mykiss Walbaum fed dietary supplements. The biometric indices and the following enzymes activities were measured: acid protease and pepsin from the stomach homogenates, alkaline phosphatase (AP) from the small intestine and the brush border membrane, total proteolytic enzymes and trypsin from the small intestine and liver/pancreas. Dietary garlic induced a higher pepsin activity in the stomach than lipopolysaccharide (LPS) and ginger. Conversely, dietary ginger and LPS showed a significant difference (P > 0.05) in acid protease activity compared to the controls. There was not any significant difference observed between treated groups and the controls for hepato‐pancreas proteolytic enzyme activity, except for trypsin. AP activity increased significantly with dietary garlic, ginger and LPS compared to the controls.     

Use of probiotics to control furunculosis in rainbow trout, Oncorhynchus mykiss (Walbaum)

Aerobic heterotrophic bacteria were isolated from the intestinal contents of Atlantic salmon, Salmo salar , rainbow trout, Oncorhynchus mykiss , and turbot, Scophthalmus maximus , on tryptone soya agar and De Man Rogosa and Sharpe agar, of which 11 of 177 (6% of the total) of the isolates were antagonistic to Aeromonas salmonicida . Four of these cultures, which were identified tentatively as A. hydrophila , Vibrio fluvialis , Carnobacterium sp. and an unidentified Gram-positive coccus, were beneficial to fish when fed singly or as an equi-mixture. Feed supplemented with the putative probiotics indicated survival of the organisms in the gastrointestinal tract for 7 days. Feeding with the probiotics for 7 and 14 days led to better survival following challenge with A. salmonicida . There was no indication of serum or mucus antibodies to A. salmonicida , but there was an increased number of erythrocytes, macrophages, lymphocytes and leucocytes, and enhanced lysozyme activity in the fish.     

Effects of dietary Persian oak (Quercus brantii var. persica) fruit extract on survival,growth performance,haematological and immunological parameters in rainbow trout,Oncorhynchus mykiss,fingerlings

The aim of study was to evaluate the effects of jaft (internal layer of oak fruit) extract on growth, haematological and immunological parameters in rainbow trout fingerlings. A total of 360 fish (average weight 6.25 g, total length 7.75 cm) were randomly distributed in 12 fibreglass tanks (stocking density: 1.04 g L^?1) with flow rate of 8 L min^?1. The ethanolic extraction of jaft was taken, and, then, a basal diet was supplemented with 0 (control), 0.5, 1 and 2 g kg^?1 to formulate four experimental diets. After 8 weeks, blood sampling was performed for haematological and immunological parameters. While immunological parameters such as IgM and lysozyme showed their lowest level in control group, their highest amounts appeared in 2 g kg^?1 group. C3, C4 and alternative complement activity increased in fish fed 2 g kg^?1 extract compared to control (P ? 0.05). Haematological parameters such as white blood cell, red blood cell, haemoglobin and haematocrit were enhanced in experimental groups (P ? 0.05). Survival and growth indices did not show significant changes in experimental treatments (P ? 0.05). Results indicated feeding rainbow trout with Persian oak extract at 0.5, 1.0 and 2.0 g kg^?1 levels significantly enhance the immunological parameters.     

Antioxidant‐related parameters,digestive enzyme activity and intestinal morphology in rainbow trout (Oncorhynchus mykiss) fry fed graded levels of red seaweed,Gracilaria pygmaea

This study was conducted to investigate the effects of dietary red seaweed, Gracilaria pygmaea level on growth, antioxidant‐related parameters, digestive enzyme activity and intestinal morphology of rainbow trout (Oncorhynchus mykiss) fry. Five isocaloric and isonitrogenous diets were formulated to contain four G. pygmaea levels (30 (GL‐30), 60 (GL‐60), 90 (GL‐90) and 120 g/kg (GL‐120)), and a control diet was used, without inclusion of seaweed. Results of the feeding trial indicated that final body (FBW: 2.8–3.5 g) and specific growth rate (SGR: 4.8–5.2) were significantly improved when 60 g/kg G. pygmaea was supplemented in the diets. However, there was a significant reduction (p < .05) of final body weight (FBW) and specific growth rate (SGR) in fish fed 120 g/kg G. pygmaea. Protease activity was significantly lower in fish fed GL‐120 diet when compared to GL‐30 or control (p < .05). Lipase was significantly affected by dietary seaweed regardless its level of supplementation (p < .05). The inclusion of the Gracilaria in the diet led to evident changes in the fish antioxidant status with significant reduction of superoxide dismutase, glutathione peroxidase activity and lipid peroxidation products. The histological study demonstrated that all groups of fish displayed normal morphology of anterior intestine and pyloric caeca. Villi absorptive area in the anterior intestine of treatment groups GL‐90 and GL‐120 significantly decreased (p < .05). Overall, the results obtained in this study indicate that dietary G. pygmaea supplementation up to 90 g/kg improves growth performance in rainbow trout fry without compromising antioxidant responses and digestive function.     

不同硒源对虹鳟生长性能及抗氧化能力的影响

在以鱼粉为主要蛋白源的基础饲料中分别添加亚硒酸钠和硒酵母,使饲料中硒的含量达到1．5％、2．0％、2．5％、3．0％。基础饲料设为对照组,不添加外源硒,对照组的硒含量为1．0％。在水温10℃～15℃、溶解氧5．6mg／L的条件下,对初始体重150g的虹鳟进行为期50d的生长对比试验。实验结束后取鱼的肝脏及血清,分别测定其超氧化物岐化酶（SoD）、谷胱甘肽过氧化物酶（GSH—Px）活力及总抗氧化能力（T—AOC）、丙二醛（MDA）的值。结果表明：虹鳟鱼的增重率、饲料利用率各组之间差异不显著。各组之间的SOD、GSH—Px、T—AOC、MDA没有显著差异。因此在以鱼粉为主要蛋白源的虹鳟鱼饲料中添加外源硒,对虹鳟的生长及抗氧化能力没有显著影响。     

Effects of canola meal on physiological and biochemical parameters in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (initial body weight 4.16 ± 0.25 g) were fed diets [crude protein 420 g kg^?1; gross energy 18.7 MJ kg^?1 dry matter (DM); crude fat 110 g kg^?1] containing graded levels of either a canola meal (crude protein 350 g kg^?1 DM) supplemented with DL‐methionine as partial fish meal protein. A growth trial was conducted over 16 weeks at a water temperature of 12 ± 1 °C. At the end of the growth trial, in addition to body composition analyses, plasma tri‐iodothyronine (T₃) and thyroxine (T₄), cholesterol and liver fatty acid composition were measured. Replacement of fish meal with canola meal (100–570 g kg^?1 replacement) did not affect on growth performance. At 16th week, plasma cholesterol levels were reduced in fish fed all diets in comparison with 8th week. Plasma T₄ levels were significantly higher in the canola meal‐fed fish sampled after 16 weeks, but no significant differences in T₃ levels were obtained (P > 0.05). Proximate compositions were affected by dietary treatments. The liver fatty acid composition reflected that of the diet with a higher level of polyunsaturated (n‐6) fatty acids in fish fed diet canola meal and a higher content in n‐3/n‐6 ratio in fish fed diet without canola meal. These studies show that canola meal has potential to replace substantial levels of fish meal in diets for carnivorous fish without compromising performance.     

Effects of various diet formulations (experimental and commercial) on the morphology of the liver and intestine of rainbow trout (Oncorhynchus mykiss) juveniles

The aim of the present study was to evaluate the effects of three formulated diets: wheat gluten protein‐based diets supplemented with Lys–Gly dipeptide (PP) or free lisine and glycine (AA), and a control diet without lysine supplementation (CON), two commercial starters: Aller Futura (AF), Aglo Norse (AN) and frozen Chironomidae larvae (CH) for on the growth and digestive system development of rainbow trout. The experiment lasted 28 days and survival at the end of the experiment was the highest in the group fed AF (87.9±4.2%) and the lowest in the group fed the CON diet (74.0±4.3%). Fish fed the CON diet showed a significantly lower crude protein content, and the AA group had a significantly higher lipid level (P≤0.05) in body carcass compared with the other groups. The highest density of intestinal goblet cells (P≤0.05) was observed in fish fed the CON diet, while the lowest density was seen in the distal intestine in the AF group. The hepatocyte cytoplasm of all fish stored more glycogen than lipids. These results indicate that wheat gluten protein‐based diets supplemented with dipeptide Lys–Gly (PP) or free lysine and glycine (AA) supported growth, protein efficiency rate and intestine epithelium homeostasis. On the other hand, fish fed CON (lysine‐deficient diet) showed lower survival and growth rate, and disturbances of intestine epithelium homeostasis, probably as a result of lysine deficiency.     

Effects of dietary visceral protein hydrolysate of rainbow trout on growth performance,carcass composition,digestibility and antioxidant enzyme in juvenile Oncorhynchus mykiss

The purpose of this study was to investigate the effects of dietary visceral protein hydrolysate (VPH) of rainbow trout on performance of juvenile Oncorhynchus mykiss. The antioxidant property of VPH was 85% ± 1.6%. Four diets were prepared including VPH free as the control and three diets with 5, 10 and 20 g/kg of VPH inclusions. Juvenile rainbow trouts (n = 252, 9.74 ± 0.22 g) were randomly distributed to experimental tanks. Final results showed the maximum amounts of weight gain and SGR and the lowest FCR value in fish fed with 10 g/kg VPH (p < .05). The highest carcass protein and fat contents were observed in 10 g/kg VPH treatment and the control diet, respectively (p < .05). The largest fat and dry matter digestibility were recorded in fish fed by 5 g/kg VPH (p < .05), while the control and 10 g/kg VPH diets showed the highest levels of protein digestibility (p < .05). Dietary inclusion of VPH improved SOD enzyme activity (p < .05). The results indicate that a diet containing 10 g/kg of VPH inclusion can improve growth performance and some other examined factors in juvenile O. mykiss.     

Evaluations of Hilyses™, fermented Saccharomyces cerevisiae,on rainbow trout (Oncorhynchus mykiss) growth performance,enzymatic activities and gastrointestinal structure

This study examined the effects of Hilyses?, fermented Saccharomyces cerevisiae (S. cerevisiae), on rainbow trout growth performance, haematological parameters, digestive enzyme activities and gastrointestinal structure. Rainbow trout (mean weight 100–110 g) were fed dietary Hilyses? (5 g kg^?1) and control diet without Hilyses? for 50 days. Results of this study demonstrated that yeast supplementation in treatment group resulted in increased feed intake, followed by improved feed conversion ratio (FCR) and growth performance. Significant increases were also observed in trypsin and amylase activities in juvenile fish fed treatment diet. Light microscopy demonstrated that both groups of fish displayed normal morphology of proximal intestine and pyloric caeca. In yeast‐treated group, higher density of the goblet cells per villus in the proximal intestine was shown. No effects on haematological parameters and carcass chemical composition were noted. It is therefore possible to use fermented S. cerevisiae supplementation to significantly improve the gastrointestinal structure and growth performance in rainbow trout.     

Probiotic applications for rainbow trout (Oncorhynchus mykiss Walbaum) I. Effects on growth performance,feed utilization,intestinal microbiota and related health criteria

The effect of dietary probiotics (Bacillus subtilis, Bacillus licheniformis and Enterococcus faecium) used singularly and synergistically on the growth performance, intestinal microbiota and health status of rainbow trout (Oncorhynchus mykiss Walbaum) were assessed after 10 weeks feeding on supplemented diets. No significant improvements of weight gain or specific growth rate were observed in the probiotic fed groups. However, a significant improvement of feed conversion ratio was observed in the group fed E. faecium. High levels of probiotic species were observed in the posterior gastrointestinal tract as transient digesta‐associated populations and potentially resident mucosal populations. Bacillus subtilis and B. licheniformis levels accounted for 36% of the total culturable microbial population adhered to the mucosa and 62% in the digesta. E. faecium levels accounted for 45% of the mucosal population and 89% of the population in the digesta. An increase of serum lysozyme activity was observed in the fish fed diets containing the Bacillus probionts and elevated leukocyte levels were observed in fish fed diets containing Bacillus + E. faecium synergistically. The results of the current study demonstrate potential for B. subtilis, B. licheniformis and E. faecium to improve feed utilization, modulate intestinal microbiota and the health status of rainbow trout.     

Histology and growth performance in rainbow trout (Oncorhynchus mykiss) in response to increasing dietary concentration of sparteine,a common alkaloid in lupins

This study evaluated the effects of sparteine, a lupin alkaloid, on growth and organ histology in rainbow trout. Eight diets with increasing concentrations of sparteine (0, 50, 100, 250, 500, 1000, 2500 and 5000 mg kg^?1) were fed to triplicate groups of 61‐g fish for 62 days. Survival was not affected by the dietary treatments. Weight gain, feed conversion efficiency and feed intake decreased in a quadratic manner for sparteine levels above 100 mg kg^?1. No effects were observed at inclusion levels ≤100 mg kg^?1. Whole‐body lipid and dry matter was depleted in a quadratic manner, while protein and ash were not affected. No tissue alteration attributable to sparteine alkaloid intake was found in liver, kidney, spleen or mid and distal intestines. At sparteine levels above 1000 mg kg^?1 of diet, the weight of the intestines and the liver relative to body weight decreased, whereas the weight of the spleen increased. These effects were likely associated with low feed intake and starvation. These results indicate that dietary sparteine alkaloid primarily reduced palatability, but did not impair the health of the fish. The level of sparteine should be kept below 100 mg kg^?1 in trout diets to ensure rapid growth.     

Effect and interaction of rainbow trout strain (Oncorhynchus mykiss) and diet type on growth and nutrient retention

Eight strains of rainbow trout were introgressed to develop a single strain (H‐ARS) that was selected for faster growth when fed a fishmeal‐free, plant‐based diet (Selection Diet). For four generations, families from these crosses were fed the Selection Diet and selected for increased weight gain. Growth and nutrient retention were compared among H‐ARS and two parental strains, the House Creek (HSC) and Fish Lake (FL) fed either a fish meal or Selection diet for 12 weeks. There was a significant effect of strain (P < 0.01), but not diet on weight gain, and a significant interaction of strain by diet (P < 0.05). The H‐ARS trout gained more weight averaged across diet (991% of initial wt.) than the HC (924%) or FL trout (483%). The FL trout fed the fish meal diet gained more weight than FL trout fed the selection diet (510% vs 456%). Conversely, H‐ARS trout fed the plant‐based diet gained more weight than those fed the fish meal diet (1009% vs 974%). HSC trout had similar weight gain fed either diet (922% vs 926%). A significant effect of strain on protein retention (P < 0.01) was observed, along with a significant strain by diet interaction (P < 0.02). The results demonstrate that rainbow trout can be selectively improved to grow on a plant‐based diet.     

Probiotic applications for rainbow trout (Oncorhynchus mykiss Walbaum) II. Effects on growth performance,feed utilization,intestinal microbiota and related health criteria postantibiotic treatment

The effect of dietary probiotics (Bacillus subtilis, Bacillus licheniformis and Enterococcus faecium) was assessed on rainbow trout (Oncorhynchus mykiss Walbaum) previously treated with oxolinic acid. After feeding on supplemented diets for 10 weeks growth performance, feed utilization, gastrointestinal colonization and health status were assessed. B. subtilis + B. licheniformis fed fish displayed a significant improvement of feed conversation ration (FCR), specific growth rate (SGR) and protein efficiency ratio (PER). High levels of probiotic species were observed in the posterior gastrointestinal tract as transient digesta associated populations and potentially resident mucosal populations. Levels of Bacillus spp. reached log 3.74 CFU g^?1 on the mucosal epithelium and log 7.41 CFU g^?1 in the digesta of fish fed diets supplemented with B. subtilis and B. licheniformis. Enterococci levels reached log 2.84 CFU g^?1 on the mucosa and log 7.78 CFU g^?1 in the digesta of fish fed E. faecium supplemented diets. Feeding trout the Bacillus probionts alone or synergistically with E. faecium resulted in elevated leucocyte levels. The results of the current study demonstrate a potential role of probiotics for stabilizing/reinforcing the gastrointestinal microbiota after antibiotic treatment. This could reinvigorate the intestinal defensive barrier mechanism and provide protection against secondary potential pathogens.     

Use of probiotics to enhance growth,stimulate immunity and confer disease resistance to Aeromonas salmonicida in rainbow trout (Oncorhynchus mykiss)

An 8‐week feeding trial was conducted to evaluate the effects of dietary probiotics on growth, non‐specific immune responses and disease resistance in juvenile rainbow trout, Oncorhynchus mykiss. Fish averaging 5.8 ± 0.8 g (mean ± SD) were fed one of the five experimental diets; one control (Cont), and four other diets were prepared by supplementing single probiotics 1 (Bacillus subtilis; SP₁, 0.5%), single probiotics 2 (Bacillus licheniformis; SP₂, 0.5%), multi‐probiotics (B. subtilis + B. licheniformis; MP, 0.5%) and oxytetracycline (OTC) at 5 g OTC kg^?1 diet. After 8 weeks of the feeding trial, weight gain and specific growth rate of fish fed SP₁, SP₂ and OTC diets were significantly higher than those of fish fed Cont diet (P < 0.05). Superoxide dismutase (SOD) and lysozyme activities of fish fed SP₁, SP₂ and MP diets were significantly higher than those of fish fed Cont diet (P < 0.05). There were no significant differences in SOD and lysozyme activities among fish fed SP₁, SP₂, MP and OTC diets. In challenge test with Aeromonas salmonicida for 15 days, fish fed SP₁, SP₂ and MP diets showed significantly higher cumulative survival rate than those of fish fed Cont diet (P < 0.05). However, there were no significant differences in cumulative survival rate among fish fed SP₁, SP₂, MP and OTC diets. Although there was a little advantage in fish fed MP diet in terms of non‐specific immune responses, single or multi‐probiotics are equally effective statistically. These results indicate that single or multi‐probiotics had equal beneficial effects as an antibiotic replacer on growth performance, non‐specific immune responses and disease resistance in juvenile rainbow trout.     

Identification of a novel gill-specific calpain from rainbow trout (Oncorhynchus mykiss)

Calpains are calcium-dependent neutral proteases responsible for many cellular functions. The two forms of calpain ubiquitously expressed in mammalian tissues are known as μ-calpain and m-calpain. We report here the identification of a novel calpain that is similar to but distinct from the μ- and m-calpains in rainbow trout. The cDNA of the novel gene is 2623 bp in length with a single open reading frame. The predicted protein (676 amino acids) contains the conserved calpain characteristic domains that include: domain I (pro peptide), II (cysteine catalytic site), III (electrostatic switch), and IV (calmodulin-like) with five Ca²⁺-binding EF hands. Northern blot and RT-PCR analyses demonstrated that the novel calpain gene is predominantly expressed in rainbow trout gills. Comparison of the novel protein with the ubiquitously expressed calpains and several mammalian tissue-specific calpains revealed that the novel calpain is an orthologue of the mammalian digestive tract specific calpain (calpain 9).     

Effect of dietary inclusion of lysozyme on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss)

This study was conducted to evaluate the effect of dietary lysozyme supplementation on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss). Graded levels of lysozyme [0 (control), 150, 300, 450 and 600 mg kg^?1 diet] were fed to fish (initial average weight 7.76 g) for 10 weeks. Dietary lysozyme supplementation regardless of inclusion level generally improved the growth, feed utilization and nutrient retention, but significant differences were mainly observed between the 450 or 600 mg kg^?1 lysozyme group and the control group. Lysozyme supplementation generally decreased the plasma aspartate aminotransferase and alanine aminotransferase (ALT) activities, but significant difference was only observed in the ALT activity between the 450 mg kg^?1 lysozyme group and the control group. In contrast, lysozyme supplementation generally increased the plasma alkaline phosphatase and lysozyme activities, but significant difference was only observed in the lysozyme activity between the 600 mg kg^?1 lysozyme group and the control group. Lysozyme supplementation generally increased the plasma antioxidant activities of enzymes (including superoxide dismutase, glutathione peroxidase and catalase) and total antioxidant capacity, but decreased the plasma malondialdehyde level. These results suggest that dietary 450–600 mg kg^?1 lysozyme inclusion may improve the growth and non‐specific immune response of rainbow trout.