Growth performance,nutrient digestibility and intestinal morphology of rainbow trout (Oncorhynchus mykiss) fed graded levels of the yeasts Saccharomyces cerevisiae and Wickerhamomyces anomalus

In a 10‐week study, we evaluated the effects of replacing 20%, 40% or 60% of fishmeal (present in control diet at 300 g/kg) on a digestible protein basis with yeast Saccharomyces cerevisiae or a yeast mixture of Wickerhamomyces anomalus and S. cerevisiae on growth performance, nutrient digestibility, nutrient retention and intestinal health of rainbow trout (Oncorhynchus mykiss). Triplicate tanks with 35 rainbow trout (144.7 ± 25.1 g mean ± SEM) were fed rations of 1.5% of total biomass per tank. Replacement of 60% of fishmeal with yeast mixture resulted in lower specific growth rate of 1.0% versus 1.2%/day for other diets. Apparent digestibility coefficients for crude protein and most amino acids were highest in fish fed fishmeal‐based diet, with similar values for fish fed the diet with 20% replacement with yeast mixture. Diet with 20% replacement with yeast mixture resulted in highest phosphorus digestibility. Replacement of 60% of fishmeal with S. cerevisiae resulted in oedematous mucosal fold tips in the proximal intestine. The results of this study suggest that these yeasts can replace up to 40% of fishmeal under current inclusion levels in diets for rainbow trout without compromising growth performance, nutrient digestibility or intestinal health.     

Partial and total replacement of fishmeal by a blend of animal and plant proteins in diets for Seriola dumerili: Effects on performance and nutrient efficiency

A 154‐day trial was performed to assess the use of an alternative protein blend (corn gluten, krill and meat meal) as a substitute for fishmeal in diets for juvenile yellowtail, using four isolipidic (140 g/kg) and isoenergetic diets (24 MJ/kg) with the same digestible protein content (50%). The control diet was FM100, without replacement, and in FM66, FM33 and FM0, fishmeal was replaced at 33 g/kg, 66 g/kg and 100 g/kg, respectively. At the end of the experiment, no differences in growth parameters were observed. Fish fed the FM0 diet exhibited the lowest survival (23%). This high mortality may be due to different factors, such as a dietary amino acid imbalance or some antinutrient factors contained in the alternative ingredients. Feed intake, feed conversion ratio, digestible protein intake and protein efficiency ratio were similar in all diets. However, digestible energy intake and protein efficiency retention were lowest in fish fed the FM0 diet. Apparent digestibility coefficients for protein, energy and amino acids diminished as a substitution for fishmeal increased. Significant differences were observed in the diet whole‐fish body profile amino acid retention (AAR) ratio for the seven essential amino acids. In summary, total fishmeal replacement by the blend assayed was not feasible for yellowtail. The FM66 diet resulted in good growth, high survival and good nutrient efficiency.     

The effect of dietary protein source (fishmeal vs. plant protein) and non‐starch polysaccharide level on fat digestibility and faecal bile acid loss in rainbow trout (Oncorhynchus mykiss)

This study investigated in rainbow trout (Oncorhynchus mykiss) if diet composition and feeding level affect faecal bile acid loss, and whether this reflects on the apparent digestibility coefficient (ADC) of fat. Six diets were formulated with either fishmeal or plant protein as main protein source. This created a contrast in the supply of bile acids, the bile acid precursor cholesterol, taurine and the taurine precursors (methionine + cysteine) involved in bile acid conjugation. For both protein sources, three diets were formulated with increasing inclusion of a non‐starch polysaccharide (NSP)‐rich ingredient mixture (0.0, 82.0 and 164.2 g/kg diet). This aimed at enhancing faecal bile acid loss. Fish were fed both restrictively (1.2% BW/day) and to satiation. A similar fat ADC was found when substituting fishmeal with a plant protein mixture, suggesting that the lower content of bile acids, cholesterol, taurine, methionine and cysteine in the plant‐based diets did not limit fat digestion. Faecal bile acid loss increased alongside dietary NSP level, however, only during satiation feeding and most strongly for fish fed the fishmeal‐based diets. Enhanced faecal bile acid loss was not caused by NSP‐bile acid binding/entrapment, but by an increase in faeces production. During satiation feeding, fat ADC negatively correlated with faecal bile acid loss. From this it is concluded that bile acid availability/synthesis can become limiting for fat digestion in rainbow trout under conditions that enhance faecal bile acid loss (i.e. dietary NSP level and feeding level).     

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.     

Utilization of unprocessed and fibre‐reduced oilseed cakes of rapeseed and sunflower seed in rainbow trout (Oncorhynchus mykiss W.) nutrition—Evaluation of apparent digestibility and growth performance

Two digestibility trials were carried out to determine the apparent digestibility coefficients (ADCs) for crude protein (CP), crude lipid (CL) and energy of unprocessed and two differently processed fibre‐reduced rapeseed and sunflower seed oil cakes (sieved oilseed cakes and oilseed cakes produced from partially dehulled seeds) in rainbow trout (40 fish per tank; four tanks per diet). Each trial was followed by a 63‐day growth trial, wherein the respective oilseed cakes with the highest ADCs were evaluated as fishmeal substitutes, based on digestible CP. Oilseed cakes of rapeseeds and sunflower seeds had low nutrient ADCs (Trial 1). Nonetheless, the protein in rapeseed cake was able to replace up to 10% of the fishmeal protein in a diet without negatively affecting performance traits (Trial 2). Fibre reduction increased the ADCs of both types of oilseed cakes substantially (Trial 3). However, when fish were fed diets with 0%, 25% and 50% fishmeal protein replaced with dehulled rapeseed or dehulled sunflower seed cake protein, performance traits decreased with increasing substitution levels (Trial 4). Nonetheless, the amount of fishmeal needed per unit weight gain was lower for all fish fed the diets containing either one of the dehulled oilseed cakes than for the reference diets.     

Salmon testes meal as a functional feed additive in fish meal and plant protein‐based diets for rainbow trout (Oncorhynchus mykiss Walbaum) and Nile tilapia (Oreochromis niloticus L.) fry

Fishery processing by‐products are a large resource from which to produce fishmeal and other products for a variety of uses. In this study, testes meal (TM) produced from pink salmon processing by‐product was evaluated as a functional ingredient in aquafeeds. Nile tilapia and rainbow trout fry were fed five isonitrogenous and isoenergetic experimental diets for 4 and 9 weeks respectively. Two diets were fishmeal‐based (FM) and three were plant protein‐based (PP). Salmon TM was added to the FM and PP diets at 7% to replace 20% of fishmeal protein (FMTM and PPTM respectively). An additional control diet was prepared in which fishmeal was added to the PP diet to supply an equivalent amount of protein as supplied by TM (PPFM). Inclusion of TM in both the FM‐ and PP‐based diets resulted in higher final body weights, although differences were only significant between rainbow trout fed FM or FMTM diets. Similar differences were calculated for other indices of fish performance, e.g. specific growth rate, feed conversion ratio, protein efficiency ratio and protein retention efficiency. Feed intake was significantly higher for fish fed FMTM compared with FM in rainbow trout. For tilapia, final weights were numerically higher, but not significantly different for fish fed diets containing TM compared with non‐TM diets (FM vs. FMTM; PP vs. PPTM). Performance of trout or tilapia fed the PPFM diet did not increase compared with the PP diet. The results indicate that TM addition to both FM and PP diets increased feed intake and also increased metabolic efficiency, demonstrating that TM can be a functional ingredient in aquafeeds.     

Optimizing zinc supplementation levels of rainbow trout (Oncorhynchus mykiss) fed practical type fishmeal‐ and plant‐based diets

Rainbow trout (23.1 ± 0.4 g) were fed either a fishmeal‐ or plant‐based diet supplemented with various levels of zinc (0, 15, 30, 60 or 120 mg kg^?1) for 12 weeks. Trout fed the fishmeal diet had significantly higher weight gain than with the plant‐based diet. Zinc supplementation in the fishmeal diet had no effect on growth performance, suggesting that additional dietary supplementation of zinc is not required. However, in trout fed the plant‐based diet, growth increased significantly up to 30 mg kg^?1 zinc after which growth was not affected. Trout fed the plant‐based diet containing no zinc exhibited severe growth retardation, and in fish fed the 0 and 15 mg kg^?1 zinc diets, cataracts were present. Use of broken‐line quadratic modelling suggests that dietary supplementation of zinc needed to prevent deficiency and promote adequate growth in rainbow trout fed the plant‐based diet in this study was 30.1 mg kg^?1 (80 mg kg^?1 total dietary zinc). This is higher than the NRC (2011, Nutrient Requirements of Fish and Shrimp) dietary recommended level of 15 mg kg^?1 for rainbow trout. Following the NRC recommendation could lead to zinc deficiency in rainbow trout fed a plant‐based diet.     

Substitution of fish meal by sesame oil cake (Sesamum indicum L.) in the diet of rainbow trout (Oncorhynchus mykiss W.)

The present study evaluated the nutritional value of sesame oil cake (SOC) in rainbow trout fry (initial body weight of 1.42 g) in a growth trial performed for 45 feeding days at 15 ± 1 °C. A series of five isonitrogenous (380 g digestible protein kg^?1 dry matter (DM)) and isoenergetic (18.1 MJ digestible energy kg^?1 DM) diets were formulated in which the digestible SOC protein progressively replaced 0%, 13%, 26%, 39% and 52% of the digestible protein of a high quality fish meal (D0‐D52). Growth rate of fry significantly improved in fish fed SOC diets compared to the fishmeal control diet (D0) whatever the SOC inclusion level. This positive effect on growth was mainly related to a marked improvement of voluntary feed intake. The decrease of feed efficiency observed with increasing SOC was entirely explained by the reduction of DM and energy digestibilities with SOC incorporation. Nitrogen retention efficiency (nitrogen gain/nitrogen intake) was high (40–41%) and significantly reduced only in fish fed D52 (37%). Our results suggest that SOC can be a suitable protein source for a carnivorous fish and replace at least half of the fishmeal protein (without amino acid supplementation) without growth reduction in rainbow trout fry.     

The effect of varying dietary digestible protein and digestible non‐protein energy sources on growth,nutrient utilization efficiencies and body composition of carp (Cyprinus carpio) evaluated with a two‐factorial central composite study design

To determine optimized dietary nutrient supply for common carp (Cyprinus carpio), nine isoenergetic diets were formulated according to a two‐factorial central composite design on digestible basis. Digestible protein contents (DP) in diets ranged from 208.8 to 251.2 g/kg, and digestible fat‐to‐digestible carbohydrate energy ratios (DEF/DEC) varied from 0.79 to 1.21. Carp were fed four times a day at a daily feeding rate of 2.5 g/kg body weight for 56 days. Optima of responses were determined by applying the standard least squares method according to response surface methodology. All diets resulted in excellent performance with feed conversion ratios lower than 1 and digestible protein efficiency ratios (PER_dig) higher than 4.6. For most parameters, calculated extreme values were minimum points, except for FCR, retention efficiencies of digestible arginine (RetArg_dig) and of digestible methionine (RetMet_dig), being maximum points, and retention efficiencies of digestible isoleucine, digestible sulphuric amino acids and digestible lysine, being saddle points. Highest growth and feed utilization efficiency were graphically determined for a diet containing 208.8 g/kg DP/1.21 DEF/DEC. Body lipid was optically increased for 251.2 g/kg DP/0.79 DEF/DEC in comparison with 208.8 g/kg DP/1.21 DEF/DEC.     

Supplementation of plant‐based diets for rainbow trout (Oncorhynchus mykiss) with macro‐minerals and inositol

Replacement of fish meal with plant products in aquafeeds results in the elimination of dietary compounds which may be important for optimal growth and physiology. A study was conducted to determine if supplementation with macro‐minerals and/or inositol would improve performance of rainbow trout (Oncorhynchus mykiss) fed a plant‐based diet. Four iso‐caloric and iso‐nitrogenous diets (40 g kg^?1 protein and 15 g kg^?1 lipid) were formulated and consisted of a fish meal‐based control diet (control) and three plant‐based experimental diets. Plant‐based diets were supplemented with either macro‐minerals and inositol (+MM+I), no macro‐minerals with inositol (?MM+I), and no macro‐minerals and no inositol (?MM?I). Sodium chloride, potassium chloride and magnesium oxide were the sources used in the macro‐mineral premix. There was no effect of diet on survival, but there was an effect of diet on weight gain, FCR, feed intake, HSI and nutrient retentions. Significant liver pathology was observed in trout fed plant‐based diets without MM supplementation. Supplementation of MM and inositol significantly improved weight gain of trout fed a plant‐based diet. Supplementation of MM and/or inositol also improved PRE and ERE. This study demonstrates the importance of supplementing these nutrients to trout fed fish meal free diets.     

Optimization of Dietary Manganese for Rainbow Trout,Oncorhynchus mykiss,Fed a Plant‐based Diet

Juvenile rainbow trout were fed a plant‐based diet supplemented with inorganic Mn added at 0, 0.5, 1, 2, 4, 8, 16, or 32 mg/kg diet for 12 wk. Whole‐body Mn concentrations increased with increasing dietary levels. Rainbow trout fed 2–8 mg Mn/kg diet exhibited weight gain that was significantly higher than fish fed 0, 0.5, 1, 16, and 32 mg Mn/kg diet. Feed conversion ratio (FCR) showed a similar trend, where FCR values decreased with increasing dietary Mn until concentrations reached 8 mg Mn/kg, after which they increased. A rational nonlinear model (R² = 0.84) fit to weight‐gain data showed that the optimal predicted supplementation level for Mn was 4.8 mg/kg diet. The optimal predicted supplementation level for Mn was similar for FCR (5 mg Mn/kg diet). The predicted 5 mg/kg diet of supplemental Mn required for the plant‐based diet formulation examined in this study is lower than the National Research Council–recommended supplementation level of 12 mg/kg. However, due to potential differences in bioavailability or retention of Mn among plant‐protein sources, the level of dietary supplementation for optimal growth could be slightly higher or lower depending on the dietary formulation.     

Use of plant‐based protein concentrates as replacement for fishmeal in practical diets for the Pacific white shrimp (Litopenaeus vannamei) reared under high stocking density and low salinity conditions

Two feeding trials were conducted to investigate the effect of replacing fishmeal with a combination of soy and corn protein concentrate (1:1 ratio) on growth performance of the Pacific white shrimp (Litopenaeus vannamei). A basal diet containing 200 g/kg fishmeal was systematically reduced (200, 150, 100, 50 and 0 g/kg) with protein concentrate on an isonitrogenous basis. Additionally, two diets containing 0 or 50 g/kg fishmeal were supplemented with lysine and methionine to evaluate possible limitations in EAAs. Each diet was randomly fed to five replicate tanks (15 shrimp per 75 L aquaria) reared in an indoor clear water system (Trial 1), or four replicate circular tanks (100 shrimp per 800 L) reared in outdoor green water system (Trial 2). In trial 1, results indicated a slight decrease in shrimp performance as fishmeal was replaced at the highest levels. Meanwhile, the supplementation of lysine and methionine to the diets did not result in shifts in survival, growth or FCR. In trial 2, there were no significant differences in growth performance across the tested diets. This study demonstrated that plant‐based protein concentrates can be used to replace fishmeal in practical shrimp diet in clear and green water under high stocking density.     

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.     

Effect of protein source and nutrient density on growth efficiency, histology and plasma amino acid concentration of rainbow trout (Oncorhynchus mykiss Walbaum)

The effects of protein source and nutrient density on growth efficiency, nutrient digestibility and plasma amino acid concentrations of rainbow trout were evaluated. A 3 by 2 factorial treatment design with three protein sources, fish meal–barley (F–B), plant concentrates (PC) and plant meals (PM), and two nutrient densities were used. A commercial reference diet was also fed. Triplicate tanks of 30 fish (initial wt. 28 g) were fed each diet, and the final weight averaged 240 g fish⁻¹. Protein source and nutrient density affected feed intake, weight gain and feed conversion ratio. Weight gain of trout fed the PC and PM diets was approximately 10% less than fish fed the F–B diets. Protein retention was affected by protein source, but not nutrient density, and was the highest for the fish fed diets containing fish meal and the lowest for the fish fed PM diets. Apparent digestibility coefficients and apparent amino acid availabilities of the diets corresponded with differences in weight gain. This study provides further evidence that growth rates of trout fed fish meal‐free diets, using conventional and concentrated plant protein ingredients, are good but some limitation to growth exists in the fish meal‐free diets.     

Partial to total replacement of fishmeal by poultry by‐product meal in diets for juvenile rainbow trout (Oncorhynchus mykiss) and their effect on fatty acids from muscle tissue and the time required to retrieve the effect

Triplicate groups of rainbow trout (Oncorhynchus mykiss) (1.4 ± 0.1 g) were fed experimental diets containing four levels of protein substitution to totally replace fishmeal with poultry by‐product meal (0, 33, 67 and 100%). Fishmeal (FM) from tuna fish by‐products and poultry by‐product meal ‘pet food grade' (PBM) were used. Diets were formulated to be isonitrogenous (43.5% crude protein) and isolipidic (12.5% crude fat). After 80 days of feeding, no significant differences were found in terms of thermal unit growth coefficient (TGC). However, the EPA levels in muscle tissue among treatments 0PBM, 24PBM and 44PBM were found to be significantly higher than those for the 59PBM diet. Nevertheless, a re‐feeding period with the control diet showed that 28 days was long enough to regain the FA profile needed. We concluded that PBM used up to 44% in diets for juvenile rainbow trout can be used without a significantly decrease in EPA and DHA under the present conditions. The use of a whole fishmeal diet could be an important strategy to recuperate the fatty acid profile obtained when trout is feed on PBM basis. It will be important to perform longer experiments with larger fish to confirm these results.     

Effects of phytase pretreatment of soybean meal and phytase-sprayed in diets on growth, apparent digestibility coefficient and nutrient excretion of rainbow trout (Oncorhynchus mykiss Walbaum)

Rainbow trout were fed a diet containing phytase-sprayed and phytase-pretreated soybean meal with different phytase levels. The single factor random block design was used to analyze the effects on rainbow trout of dietary phytase supplementation on growth performance, nutritional ingredient digestibility and nutrient excretion. After 90 days, the results showed that feed conversion ratio (FCR) and protein efficiency ratio (PER) were significantly improved and specific growth rate (SGR) was not affected by spraying phytase, but SGR, FCR and PER were not significantly improved by phytase pretreatment. A digestibility trial conducted after the feeding trial showed that apparent digestibility coefficient (ADC) of diet protein and minerals was increased with phytase supplementation. However, there was a negative effect of phytase on the ADC of lipid. The excretion experiment showed that the supplementation of phytase resulted in decreased nutrient excretion in feces, but lipid excretion was slightly increased with phytase supplementation. In addition, the results of P excretion and ADC of P analyzed by t-test showed that phytase pre-treatment method should be a more rational method than the spraying method. The results of SGR, ADC of P and P excretion analyzed by quadratic regression indicated that 2,000–3,000 U/kg levels by the spraying method could be a rational range of phytase supplementation, and about 1,000 U/kg should be an optimal level by the pretreatment method. Thus, use of phytase in rainbow trout feeds can have economic and environmental benefits.     

Fishmeal levels can be successfully reduced in white shrimp (Litopenaeus vannamei) if supplemented with DL‐Methionine (DL‐Met) or DL‐Methionyl‐DL‐Methionine (Met‐Met)

The main objective of this study was to evaluate the effect of methionine supplementation when reducing fishmeal levels in diets for white shrimp (Litopenaeus vannamei). Tested diets consisted of a positive control with 260 g/kg fishmeal (D1), two negative controls with 100 g/kg fishmeal and no amino acid (AA) supplementation (D2) or supplemented with lysine but not methionine (D3), and four additional diets with 100g/kg fishmeal supplemented with increasing levels of DL‐Met (1.0, 2.0 or 3.0 g/kg) (D4, D5, D6) or Met‐Met (1.0 g/kg) (D7). Each diet was fed to four groups of 30 shrimp for 8 weeks at a daily rate of 70 g/kg body weight. Reduction in fishmeal from 260 g/kg down to 100 g/kg did not significantly affect survival rate, feed conversion ratio (FCR), protein efficiency ratio (PER) or protein retention efficiency (PR%) of white shrimp. However, growth performance (final body weight, FBW; weight gain, WG; specific growth rate, SGR) was reduced when dietary fishmeal level was reduced from 260 g/kg (D1) to 100 g/kg without methionine supplementation (D2). The growth performance (FBW, WG and SGR) of shrimp was significantly increased by supplementation of the 100 g/kg fishmeal diet with increasing levels of DL‐Met (p < .05). Same performance as positive control (D1) was achieved with diets containing 100 g/kg fishmeal and supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. The highest values of growth performance (FBW, WG and SGR) were found in shrimp fed D6 and D7 diets, which were significantly higher than those of shrimp fed D2 and D3 diets (p < .05) but without statistical differences with shrimp fed D1, D4 and D5 diets (p > .05). The highest values of whole‐body and muscle protein contents were found in shrimp fed D1 diet, which were significantly higher than those of shrimp fed all other diets (p < .05). The highest value of intestinal tract proteolytic enzyme activity was found in shrimp fed Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) and 3 g/kg DL‐Met‐supplemented diet (D6) (p < .05). The highest values of apparent digestibility coefficients (ADCs) of dry matter and crude protein were found in Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) (p < .05). Shrimp fed the D1 diet showed the highest value of total essential amino acid (EAA) and was significantly higher than shrimp fed D2–D3 (p < .05) but without significant difference with shrimp fed D4–D7 (p > .05). In conclusion, results showed that same performance can be achieved with diets containing 260 or 100 g/kg fishmeal supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. Moreover, supplementation of limiting methionine in low‐fishmeal diets seems to improve the digestive proteolytic activity, improving digestibility of dry matter and protein, and eventually to promote growth of juvenile white shrimp in fishmeal reduction diets.     

Evaluation of Yellow Lupin Lupinus luteus Meal as an Alternative Protein Resource in Diets for Sea-Cage Reared Rainbow Trout Oncorhynchus mykiss

The performance of sea-water reared rainbow trout Oncorhynchus mykiss fed three isonitrogenous and iso-energetic diets based on either fishmeal, solvent-extracted soybean meal or yellow lupin ( L luteus cv. Wodjil) kernel meal was evaluated. Over the course of a 10-wk study, the fastest growing fish were those fed the diet containing 50% yellow lupin kernel meal (YLM), which grew from 83.6 ± 0.7 g to 322.8 ± 3.2 g (mean ± SEM). This was not significantly faster than growth of fish fed the diet based on 50% solvent-extracted soybean meal (SBM), though it was significantly ( P < 0.05) faster than the growth of fish fed the fishmeal based diet (FSM). Growth of fish fed the experimental diets was comparable to growth of fish fed a range of commercial diets as a reference. Survival of fish fed the FSM diet was poorest of all the treatments (47.4%), though this was only significantly poorer than that of fish fed the YLM diet (88.9%). Feed intake was highest by fish fed the YLM diet (5.58 g/d) and lowest for fish fed the FSM diet (336 g/d). Reasons for these differences in feed intake were not clear, though they may be related to different levels of buoyancy and palatability among the diets. Feed conversion rate (FCR) was consistent between treatments at about 1.6:1, though given that this study was a sea-cage based experiment it is likely that considerable unaccounted feed losses occurred, thereby inflating the feed conversion value. Sensory evaluation of fish fed the three test treatments showed no overall difference in the acceptability of the fish, further supporting that solvent-extracted soybean meal and yellow lupin kernel meal both have considerable potential to replace fishmeal as a protein resource in diets for rainbow trout.     

Utilization of combined extruded soybean and corn gluten meals as feed ingredients for juvenile rainbow trout,Oncorhynchus mykiss diet

In this study, feeding experiment and subsequent digestibility trial were performed to investigate the utilization of extruded soybean meal (SBM) and corn gluten meal (CGM) as feed ingredients for juvenile rainbow trout. Plant ingredients have undergone extrusion at low temperature (100°C, LT) or high temperature (150°C, HT) for 30 s. Four isonitrogenous (44%, crude protein) and isolipidic (14%, crude lipid) diets were formulated. Control diet is fishmeal based while a combined (1:1) non‐extruded SBM and CGM for NE diet, LT SBM and LT CGM for LT diet and HT SBM and HT CGM for HT diet. Two hundred forty rainbow trout juveniles (7.8 g average body weight) were randomly divided into 12 rectangular 60 L glass aquaria and offered four different diets in triplicate. Fish were fed at satiation twice a day, six days a week for 12 weeks. Phosphorus in phytic acid level of extruded ingredients decreased through extrusion cooking. Final weight, weight gain, SGR and PER of fish fed HT diet were significantly (p < .05) higher than those fed with NE diet. Apparent digestibility coefficient for protein of LT and HT diets is significantly higher than of NE diet. The results of this study demonstrated that HT extruded SBM and CGM are suitable feed ingredients for rainbow trout diet without compromising fish growth, feed utilization and fish body composition.     

Replacement of fishmeal by canola protein concentrate in diets fed to rainbow trout (Oncorhynchus mykiss)

A dephytinized protein concentrate prepared from canola seed (CPC) was assessed for nutrient digestibility and performance in rainbow trout (Oncorhynchus mykiss). The apparent digestibility coefficients of CPC were: dry matter, 817 g kg^?1; crude protein, 899 g kg^?1; gross energy, 861 g kg^?1; arginine, 945 g kg^?1; lysine, 935 g kg^?1; methionine, 954 g kg^?1; threonine, 893 g kg^?1. A 9‐week performance trial assessed 7 diets. Fishmeal provided 940 g kg^?1 of the protein in the control diet. Test diets consisted of CPC or water‐washed CPC replacing 500 and 750 g kg^?1 of fishmeal protein; and CPC plus an attractant replacing 500 and 750 g kg^?1 of fishmeal protein. No significant differences in performance were observed (P > 0.05). A subsequent 9‐week performance trial evaluated the effect of adding CPC into compound diets containing fishmeal/soybean meal/corn gluten meal. Five diets were prepared: fishmeal provided 670 g kg^?1 of the protein in the control diet, in the remaining diets CPC was incorporated into commercial‐like trout diets at 100, 200 and 300 g kg^?1 replacement of fishmeal protein, the fifth diet included an attractant in the 300 g kg^?1 replacement diet. No significant differences in performance were obtained (P > 0.05). These studies show that dephytinized canola protein concentrate has potential to replace substantial levels of fishmeal in diets for carnivorous fish without compromising performance.