Effects of dehulling,steam-cooking and microwave-irradiation on digestive value of white lupin (Lupinus albus) seed meal for rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar)

A digestibility trial was conducted to assess the effect of dehulling, steam-cooking and microwave-irradiation on the apparent digestibility of nutrients in white lupin (Lupinus albus) seed meal when fed to rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar). Six ingredients, whole lupin seed meal (LSM), dehulled LSM, dehulled LSM steam-cooked for 15 or 45 min (SC15 and SC45, respectively) and LSM microwave-irradiated at 375 or 750 W (MW375 and MW750, respectively), were evaluated for digestibility of dry matter, crude protein (CP), lipids, nitrogen-free extractives (NFE) and gross energy (GE). The diet-substitution approach was used (70% reference diet + 30% test ingredient). Faeces from each tank were collected using a settlement column. Dehulled LSM showed higher levels of proximate components (except for NFE and crude fibre), GE and phosphorus in comparison to whole LSM. Furthermore, SC15, SC45, MW375 and MW750 showed slight variations of chemical composition in comparison to dehulled LSM. Results from the digestibility trial indicated that dehulled LSM, SC15, SC45 and MW375 are suitable processing methods for the improvement of nutrients’ apparent digestibility coefficient (ADC) in whole LSM. MW750 showed a lower ADC of nutrients (except for CP and lipids for rainbow trout) in comparison with MW350 for rainbow trout and Atlantic salmon, suggesting a heat damage of the ingredient when microwave-irradiation exceeded 350 W.     

Important considerations for methaemoglobin measurement in fish blood: assay choice and storage conditions

Spectrophotometric assays of methaemoglobin (metHb) in rainbow trout Oncorhynchus mykiss , channel catfish Ictalurus punctatus , tilapias Tilapia niloticus and Tilapia zillii and white sturgeon Acipenser transmontanus , under baseline conditions, were low (<4%) for each species, and yet higher than human values (<1%). MetHb results for a given fish species varied significantly between assays and two assays were deemed unacceptable for particular animals. For rainbow trout, white sturgeon, and the two species of tilapia, the Dubowski method gave uncharacteristically high estimates of metHb. MetHb could not measured in tilapia blood using the Evelyn & Malloy method due to spectral interference. Only the Horecker & Brackett assay worked well for all species. Storage conditions were extremely important in the quantification of metHb in rainbow trout blood. For consistent values, samples can be stored up to 4 h on ice (0° C) or at least 20 days under liquid nitrogen (− 196° C). Auto-oxidation, however, elevates rainbow trout metHb at − 20 and − 80° C. It should not be assumed that the blood of fishes and humans perform similarly during assays of metHb.     

Critical thermal minima and maxima of three freshwater game-fish species acclimated to constant temperatures

A total of 120 critical thermal maxima (CT maxima) and 120 critical thermal minima (CT minima) were determined for channel catfish, largemouth bass and rainbow trout acclimated to three constant temperatures: 20, 25 and 30 °C in catfish and bass, and 10, 15 and 20 °C in trout. Highest mean CT maximum and lowest mean CT minimum measured over these acclimation temperatures were 40.3 and 2.7 °C (catfish), 38.5 and 3.2 °C (bass) and 29.8 and ∼ 0.0 °C (trout). Temperature tolerance data were precise with standard deviations generally less than 0.5 °C. Channel catfish had the largest thermal tolerance scope of the three species while rainbow trout had the lowest tolerance of high temperatures and the highest tolerance of low temperatures. In all species CT minima and CT maxima were highly significantly linearly related to acclimation temperature. Within each species, slopes relating CT maxima to acclimation temperature were approximately half as large as those relating CT minima to acclimation temperature, suggesting that acclimation temperature has a greater influence on tolerance to low rather than high temperatures. Slopes relating both CT minima and CT maxima to acclimation temperature for the two warm-water species were similar and approximately twice those for the rainbow trout. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nutrient digestibility and growth responses of rainbow trout (Salmo gairdneri) fed different levels of cassava and rice

Seven groups of fingerling rainbow trout (Salmo gairdneri) were fed for 10 weeks on 0%, 10%, 20% and 30% of cassava or rice in isonitrogenous diets.Optimum growth and food utilisation was at 20% dietary cassava. High fibre content of the control diet did not suppress protein digestibility in this group. Rather, at all levels, protein digestibility was good and remained between 84.4% and 87.5%. However, in the control group, carbohydrate digestibility was very poor. The cassava diet which had the highest digestible energy as carbohydrate produced the best growth performance, food utilization and protein sparing. At the levels studied, the dietary carbohydrates produced no hyperglycaemic effect on the fish. There was no evidence of drastic adverse effects on the tissue and liver composition of the fish receiving these carbohydrates.     

Growth and nutrient utilization by 0 + and 1 + triploid rainbow trout, Oncorhynchus my kiss

Growth performance, protein and energy utilization in triploid rainbow trout juveniles of two yearclasses, 0 + and 1 +, were compared to diploid control groups. Growth rate, food conversion and protein efficiency ratios of triploid rainbow trout did not differ (0 + juveniles) or were slightly lower (1 + juveniles) than the diploid control. Proximate body composition was also not affected by ploidy.
Apparent digestibility coefficients (ADC) ofprotein and ofenergy, oxygen uptake, and ammonia excretion rates were not different between the two groups. Nitrogen and energy balance studies showed that digestive and metabolic utilization of the diets did not differ in triploid and diploid rainbow trout juveniles.     

Impact of black soldier fly larvae meal on the chemical and nutritional characteristics of rainbow trout fillets

The present research studied the effect of a dietary inclusion with Hermetia illucens larvae meal (Hi) on rainbow trout’s fillets chemical composition. The effect of Hi inclusion in diets on rainbow trout chemical characteristics was evaluated. Trout were fed three different diets: control (C, no Hi inclusion), 25% and 50% of substitution of fish meal with Hi (Hi25 and Hi50, respectively). Fillets were analysed to quantify proximate composition, carbohydrates percentage, colour parameters, nucleotides concentration, fatty acids profile, volatile organic compounds (VOCs) and myofibrillar and sarcoplasmic concentrations. Diets did not affect proximate composition. Contrariwise, Hi50 diet decreased fillet yellowness and both substitution percentages affected negatively adenosine monophosphate concentration. Saturated fatty acids, mostly C12 : 0, increased their contents in relation with Hi inclusion at the expense of monounsaturated and polyunsaturated (both n-3 and n-6) fatty acids. Less modifications were reported in VOCs as only heptanal and octanal concentrations were affected, no new compounds appeared in relation with Hi inclusion. No modifications in proteins patterns were shown even if myofibrillar content decreased in trout fed Hi50. The results highlighted that chemical modifications occurred in fillets were related to the chemical composition of the H. illucens meal and to the percentage of inclusion in the diet. Substitution of fish meal with a precisely percentage of H. illucens meal could be a potential future solution in order to decrease the quantity of fish meal used in aquafeeds.     

Diagnostic single nucleotide polymorphisms for identifying westslope cutthroat trout (Oncorhynchus clarki lewisi), Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) and rainbow trout (Oncorhynchus mykiss)

We describe 12 diagnostic single nucleotide polymorphism (SNP) assays for use in species identification among rainbow and cutthroat trout: five of these loci have alleles unique to rainbow trout (Oncorhynchus mykiss), three unique to westslope cutthroat trout (O. clarkii lewisi) and four unique to Yellowstone cutthroat trout (O. clarkii bouvieri). These diagnostic assays were identified using a total of 489 individuals from 26 populations and five fish hatchery strains.     

Rb-Cs ratio as an indicator of fish diet in lakes of the Patagonia, Argentina

The ratios of Rb to Cs contents were studied in five fish species from seven lakes located in the Patagonia Andean Range, Argentina in order to trace fish diet. The species studied were native velvet catfish (Diplomistes viedmensis) and creole perch (Percichthys trucha), and exotic brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvenilus fontinalis). Rainbow trout specimens from two farms were also studied, as well as fish food items and native mussels (Diplodon chilensis). Rb and Cs concentrations were determined by instrumental neutron activation analysis. A positive correlation of Cs concentration in the muscle of velvet catfish with fish length was observed, probably associated with the long biological half-life of this element in this species, whereas the Rb concentration remained constant, hence inhibiting the use of Rb-Cs ratios as a tracer in this case. Seasonal variations observed for rainbow trout and Cs concentration background bias in one of the lakes studied are also a limiting factor to the use of Rb-Cs ratios as a diet tracer. Rb-Cs ratios allowed clear differentiation of rainbow trout raised in farms from the natural specimens that lived in the same environment, in agreement with Rb-Cs ratios determined in both diets. Rb-Cs ratios in rainbow trout showed significant differences between Rivadavia and Futalaufquen lakes compared to Moreno and Nahuel Huapi lakes, which could be associated with a higher participation of plankton in the diet in the first case. No relevant variations in Rb-Cs ratios of brown trout were observed, probably because of the similarity in the diet.     

Effects of brackish water on growth, feed conversion and energy absorption efficiency by juvenile euryhaline and freshwater stenohaline fishes

Among six species of juvenile fishes (<6 months old), stenohaline species (channel catfish Ictalurus punctatus and goldfish Carassius auratus ) had their highest specific growth rate ( G ) and most efficient food conversion ratio ( E _C) and energy absorption efficiency ( I _E) in fresh water. Three of the euryhaline species (rainbow trout Oncorhynchus mykiss , striped bass Morone saxatilis and Gulf sturgeon Acipenser oxyrinchus desotoi ) had higher G and had more efficient E _C and I _E in 3 and 9‰ salinities than in lower salinities (fresh water and 1‰). For brown trout Salmo trutta (age 3–4 months), 9‰ was above the optimum level for G and E C. However, I _E for brown trout was not significantly different at 3 and 9‰ salinities. Over the salinity range tested, channel catfish had the largest change in G , E _C and I _E, while changes for euryhaline species were relatively small. Although all species tested survived and grew in all treatments, salinities as low as 1‰ adversely affected the stenohaline species, and 9‰ adversely affected brown trout.     

Absence of developmental incompatibility in hybrids between rainbow trout and two subspecies of cutthroat trout

We examined the developmental rate of hybrids between rainbow trout (Salmo gairdneri) and two subspecies of cutthroat trout: westslope cutthroat trout (Salmo clarki lewisi) and Yellowstone cutthroat trout (Salmo clarki bouvieri). These taxa show considerable genetic divergence at 42 structural loci encoding enzymes; the mean Nei's d between the rainbow trout and the two species of cutthroat trout is 0.22. We used four measures of developmental rate: time of hatching and yolk resorption, rate of increase in activity of four enzymes, and time of initial detection of seven isozyme loci. The two cutthroat trout subspecies reached hatching and yolk resorption earlier than rainbow trout. Cutthroat trout had higher relative enzyme activities than rainbow trout from deposition of eye pigment to hatching. There was no difference in the rate of increase in enzyme activity or time of initial expression of these loci between these species. Hybrids showed developmental rates intermediate or similar to that of the parental species using all measures. Our results indicate an absence of regulatory and developmental incompatibility between these taxa.This research was supported by NSF Grants ISP-8011449 and BSR-8300039. M.M.F. was supported by a postgraduate scholarship from the Natural Sciences and Engineering Research Council of Canada.     

Red beet and betaine as ingredients in diets of rainbow trout (Oncorhynchus mykiss): effects on growth performance,nutrient retention and flesh quality

The objective of the study was to evaluate the impact of different concentrations of dietary red beet and betaine on the growth performance and fish flesh quality of rainbow trout. Therefore, a control diet was compared with four diets in which two levels of red beet (14% and 28%) and betaine (0.9% and 1.63%) were incorporated in combination. The study was set up with an average body weight of 69 ± 2.2 g and finished when fish reached commercial weight (175–250 g) after 105 d. The impact of the diets was studied based on the growth performance, biometric indexes, proximal composition, protein and fat retention efficiencies and apparent nutrient digestibility by fish reared on a recirculation system. Further estimates were the effect of red beet and betaine on the flesh proximate composition and quality of the final product (water activity, colour, texture, thiobarbituric acid reactive substances and sensory characteristics). Results showed that inclusion of 14% red beet and 0.9% betaine did not affect growth, nutritive or biometric parameters and nutrient retention when compared with the control diet. However, higher levels of red beet and betaine had negative effects on growth and nutritive parameters. The tested ingredients enhanced quality parameters regardless of the concentration used. After feeding the red beet and betaine, fish flesh showed lower water activity and better textural and colour properties than the control and also a dose-dependent effect on lipid oxidation was observed.     

Use of alternative protein sources for fishmeal replacement in the diet of largemouth bass (Micropterus salmoides). Part I: effects of poultry by-product meal and soybean meal on growth,feed utilization,and health

Five isonitrogenous and isocaloric diets [containing 54, 30, 15, 10, and 5% fishmeal crude-protein (CP), dry matter (DM) basis] were prepared by replacing fishmeal with poultry by-product meal plus soybean meal to feed juvenile largemouth bass (LMB, with an initial mean body weight of 4.9 g) for 8 weeks. All diets contained 54% CP and 13% lipids. There were four tanks of fish per treatment group (15 fish/tank). The fish were fed twice daily with the same feed intake (g/fish) in all the dietary groups. Results indicated that the inclusion of 15% fishmeal protein in the diet is sufficient for LMB growth. However, some of the fish that were fed diets containing ≤ 15% fishmeal CP had black skin syndrome (characterized by skin darkening and retinal degeneration, as well as intestinal and liver atrophies and structural abnormalities). The concentrations of taurine, methionine, threonine and histidine in serum were reduced (P < 0.05) in fish fed the diets containing 5, 10 and 15% fishmeal CP, compared with the 30 and 54% fishmeal CP diets. Interestingly, the concentrations of tyrosine and tryptophan in serum were higher in fish fed diets with ≤ 15% fishmeal CP than those in the 54% fishmeal CP group. These results indicated that 15% fishmeal CP in the diet containing poultry by-product meal and soybean meal was sufficient for the maximum growth and feed efficiency in LMB but inadequate for their intestinal, skin, eye, and liver health. A reduction in dietary methionine and taurine content and the possible presence of antinutritional factors in the fishmeal replacements diets containing high inclusion levels of soybean meal may contribute to black skin syndrome in LMB. We recommend that the diets of juvenile LMB contain 30% fishmeal CP (DM basis).

     

Effects of species invasion on population dynamics,vital rates and life histories of the native species

Invasions occurring in natural environments provide the opportunity to study how vital rates change and life histories evolve in the presence of a competing species. In this work, we estimate differences in reproductive traits, individual growth trajectories, survival, life histories and population dynamics between a native species living in allopatry and in sympatry with an invasive species of the same taxonomic Family. We used as a model system marble trout Salmo marmoratus (native species) and rainbow trout Oncorhynchus mykiss (non-native) living in the Idrijca River (Slovenia). An impassable waterfall separates the stream into two sectors only a few 100 meters apart: a downstream sector in which marble trout live in sympatry with rainbow trout and an upstream sector in which marble trout live in allopatry. We used an overarching modelling approach that uses tag-recapture and genetic data (>2,500 unique marble and rainbow trout were sampled and genotyped) to reconstruct pedigrees, test for synchrony of population dynamics and model survival and growth, while accounting for individual heterogeneity. The population dynamics of the two marble trout populations and of rainbow trout were synchronous. We found higher prevalence of younger parents, higher mortality and lower population density in marble trout living in sympatry with rainbow trout than in marble trout living in allopatry. There were no differences in the average individual growth trajectories between the two marble trout populations. Faster life histories of marble trout living in sympatry with rainbow trout are consistent with predictions of life history theory.     

Characterization of calpastatin gene in fish: its potential role in muscle growth and fillet quality

Calpastatin (CAST), the specific inhibitor of the calpain proteases, plays a role in muscle growth and meat quality. In rainbow trout (RBT), we identified cDNAs coding for two CAST isoforms, a long (CAST-L) and a short isoform (CAST-S), apparently derived from two different genes. Zebrafish and pufferfish CAST cDNA and genomic sequences were retrieved from GenBank and their exon/intron structures were characterized. Fish CASTs are novel in that they have fewer repetitive inhibitory domains as compared to their mammalian counterparts (one or two vs. four). The expressions of CAST mRNAs were measured in three RBT strains with different growth rates and fillet firmness that were fed either high energy or control diets. CAST-L and S expressions were significantly lower (p < 0.01) in the strain that has the slowest growth rate and yielded the softest fillet. Strain or diet did not affect level of calpain mRNAs. However, the decrease in the CAST/calpain ratio at the mRNA level did not lead to a corresponding change in the calpain catalytic activity. Further investigation should reveal a potential use of the CAST gene as a tool to monitor fish muscle growth and fillet firmness.     

Use of soybean flour (dehulled, solvent-extracted soybean) as a fish meal substitute in practical diets for African catfish, Clarias gariepinus (Burchell 1822): growth, feed utilization and digestibility

Growth and digestibility trials were conducted using African catfish, Clarias gariepinus (Burchell 1822): (1) to obtain apparent digestibility coefficient (ADC) values for capelin fish meal, soybean flour and corn meal; (2) to formulate diets based on ADC values of the protein feedstuffs; and (3) to evaluate the effects of replacing 25%, 50% and 75% of fish meal in control diets with soybean flour on growth, feed utilization efficiency and carcass composition. Supplemental methionine was added to the diet formulation in which soybean flour replaced 75% of the diet. Diets were formulated (400 g digestible protein kg⁻¹ and 15 kJ digestible energy g⁻¹ dry diet) and fed to catfish fingerlings (13.1 ± 0.5 g) to apparent satiation twice daily for 70 days. The protein and energy digestibilities of fish meal and soybean flour were high (>90% and >80%, respectively; P < 0.05). At 75% fish meal replacement with soybean flour (without methionine supplementation), growth and feed utilization efficiency indicators were depressed compared with other diet treatments which had a similar (P > 0.05) growth and feed utilization efficiency to those fed the control diet. The carcass compositions of catfish in all diets were similar (P > 0.05) and the liver histology of catfish fed any of the diets showed no alterations. The results obtained indicate that 50% of fish meal protein in practical catfish diets can be replaced with soybean flour and that catfish can effectively utilize supplemental methionine, thereby allowing up to 75% of the dietary fish meal protein to be replaced by soybean flour.     

Evaluation of safflower meal as a protein source in diets of rainbow trout [Oncorhynchus mykiss,Walbaum, 1792)]*

The effects of different levels of safflower meal (a residue of the plant oil extraction process) in diets of rainbow trout (Oncorhynchus mykiss) on growth performance, nutrient digestibility and body composition were investigated. Four different diets containing 0% (Control group), 10% (Diet 1), 15% (Diet 2) and 20% (Diet 3) safflower meal were formulated for the fish with a mean weight of 132.70 ± 0.75 g fed for 70 days. At the end of the experiment, there were no significant differences among dietary treatments for weight gain, specific growth rate and feed conversion ratio (P > 0.05). There were also no differences in the digestibility of crude protein and crude lipid between groups (P > 0.05). Supplementation of safflower meal in the diets also had no adverse effects on body composition. The results indicate that safflower meal is a promising feed ingredient and can be used up to a concentration of 20% in the rainbow trout diet with no adverse effects on growth performance, nutrient digestibility or body composition.     

Growth and product quality of European eel (Anguilla anguilla) as affected by dietary protein and lipid sources

A 12‐week feeding trial was undertaken to evaluate the effects of partial replacement of marine raw materials in the diet with soybean meal and beef tallow on growth and product quality of European eel (Anguilla anguilla). Based on growth, feed efficiency and chemical composition, soybean meal was found to be an unsuitable ingredient for eel diets as a substitute for fishmeal (25% on a protein basis), probably because of the low digestibility of its carbohydrate content. However, beef tallow can be used to replace 50% of fish oil without reduction in growth, provided that digestible carbohydrates are present in the diet. No major effects of protein and lipid sources in the diet were found on fillet chemical composition. Sensory analysis revealed no significant differences between fish fed the control and the experimental diets, with the exception of salty taste which was significantly higher in fish fed combined soybean meal and beef tallow compared with fish fed the control diet.     

珍珠龙胆石斑鱼对7种蛋白源的表观消化率

研究测定了珍珠龙胆石斑鱼(Epinephelus fuscoguttatus♀×Epinephelus lanceolatu♂)对黄粉虫粉(TMM)、黑水虻虫粉(HIM)、乙醇梭菌蛋白(CAP)、荚膜甲基球菌蛋白(MCM)、小球藻粉(CVM)、棉籽浓缩蛋白(CPC)和秘鲁鱼粉(PFM)共7种蛋白源的表观消化率(ADCs)。试验配制1组含50%鱼粉的基础饲料,而7组试验饲料按70%的基础饲料和30%的蛋白源配制而成,8组饲料都加入0.1%氧化钇(Y₂O₃)作为外源标志物。将初始平均体重为(9.95±0.50) g的杂交石斑鱼幼鱼随机分配到0.3 m³的玻璃钢桶中,每个处理组设置3个重复(桶),每桶30尾鱼。经过5d的试验饲料饲喂驯化后,每天两次用虹吸法收集粪便样本。结果表明,7种蛋白源的干物质ADCs从高至低依次为:CVM>TMM=CAP=CPC>HIM=MCM=PFM。CVM的干物质、粗蛋白和大多数氨基酸(包括蛋氨酸和苏氨酸)的ADCs最高。而HIM的干物质、粗蛋白和大多数氨基酸的ADCs低于其他组。CAP的...     

Effects of organic plant oils and role of oxidation on nutrient utilization in juvenile rainbow trout (Oncorhynchus mykiss)

Producing organic fish diets requires that the use of both fishmeal and fish oil (FO) be minimized and replaced by sustainable, organic sources. The purpose of the present study was to replace FO with organic oils and evaluate the effects on feed intake, feed conversion ratio (FCR), daily specific growth rate (SGR) and nutrient digestibility in diets in which fishmeal protein was partly substituted by organic plant protein concentrates. It is prohibited to add antioxidants to organic oils, and therefore the effects of force-oxidizing the oils (including FO) on feed intake and nutrient digestibility was furthermore examined. Four organic oils with either a relatively high or low content of polyunsaturated fatty acids were considered: linseed oil, rapeseed oil, sunflower oil and grapeseed oil. Substituting FO with organic oils did not affect feed intake (P > 0.05), FCR or SGR (P > 0.05) despite very different dietary fatty acid profiles. All organic plant oils had a positive effect on apparent lipid digestibility compared with the FO diet (P < 0.05), whereas there were no effects on the apparent digestibility of other macronutrients when compared with the FO diet (P > 0.05). Organic vegetable oils did not undergo auto-oxidation as opposed to the FO, and the FO diet consequently had a significantly negative effect on the apparent lipid digestibility. Feed intake was not affected by oxidation of any oils. In conclusion, the study demonstrated that it is possible to fully substitute FO with plant-based organic oils without negatively affecting nutrient digestibility and growth performance. Furthermore, plant-based organic oils are less likely to oxidize than FOs, prolonging the shelf life of such organic diets.     

Growth and vitality in yellow forms of rainbow trout

The colour genes controlling the palomino and albino phenotype in the spring spawning rainbow trout [Oncorhynchus mykiss (Walbaum 1792)] strain reared at the Department of Salmonid Research Rutki, Poland were found to have strong detrimental pleiotropic effects on growth and vitality. After 5 and 9 months of rearing, the differences in mean body weights in albino, palomino and wild‐coloured trout were statistically highly significant, with albino showing the poorest, palomino as the intermediate and wild‐coloured trout having the highest growth. An identical ranking of colour phenotypes was observed for survival. The influence of colour phenotypes on both traits showed a diminishing tendency with increasing age of fish. It is concluded that alleles controlling palomino and albino colouration cannot be recommended as genetic markers. If reference groups are needed, instead of albino trout, palomino trout should be used since their pleiotropic effects are less pronounced.