Partial or total replacement of fishmeal by solvent-extracted cottonseed meal in diets for juvenile rainbow trout (Oncorhynchus mykiss)

The effect of solvent‐extracted cottonseed meal (SCSM) as a partial or total replacement of fishmeal was studied in juvenile rainbow trout (Oncorhynchus mykiss). Six experimental diets SCSM0, SCSM25, SCSM50, SCSM75, SCSM75A and SCSMT, containing a gradient of SCSM 0, 152, 305, 465, 460 and 610 g kg^?1 to replace 0, 112.5, 225, 337.5, 337.5 and 450 g kg^?1 fishmeal protein were fed to triplicate groups (initial body weight of 39.2 ± 0.1 g) for 8 weeks. The diet SCSM75A was supplemented with lysine and methionine, to be similar to SCSM0 for juvenile rainbow trout. Faeces were colleted after 4 weeks of normal feeding for apparent digestibility coefficients (ADC) of dry matter, crude protein and gross energy determination. Total replacement of fishmeal adversely affected growth performance. Fish fed with diet SCSMT had significantly (P < 0.05) lower weight gain, specific growth ratio, feed conversion efficiency (FCE) and protein efficiency ratio than fish fed with other diets. The FCE of SCSM75 and SCSM75A were significantly lower (P < 0.05) than those of fish fed with SCSM0 diets. The ADC of the dry matter of SCSM75 and SCSMT were significantly lower than the SCSM0 diet, and the ADC of crude protein and the energy of SCSMT were the lowest (P < 0.05). The ADC of threonine, proline, alanine, valine, isoleucine, leucine, lysine and methionine of fish fed with diet SCSMT were lower. Lysine and methionine supplement positively affected the ADC of SCS75A diet. There were no significant differences in the fish body composition. It is shown that SCSM can be utilized in the juvenile rainbow trout diet up to 305 g kg^?1, to replace about 50% of fishmeal protein in this experiment.     

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.     

Effect of fish meal replacement with Carinata Brassica carinata in low animal protein diets of rainbow trout Oncorhynchus mykiss (Walbaum) on trypsin activity,protein and amino acid digestibility and bioavailability

Replacement of >25% of fish meal (FM) with aerobically converted carinata meal (ACCM) in low (200g/kg) animal protein (reference = 200g/kg FM) diets of rainbow trout Oncorhynchus mykiss resulted in reduced growth, partly due to reduced feed consumption and protein utilization. In this study, we determined the effect of FM replacement with ACCM on trypsin activity, apparent digestibility coefficients (ADCs) of protein, and essential amino acid (EAA) or conditionally essential amino acid (CEAA) ADCs and bioavailability. Replacement of FM did not alter protein ADCs or trypsin activity. Replacement of >25% FM reduced all EAA and CEAA ADCs except for arginine and leucine which were only reduced by 75% FM replacement. Only serum free lysine and muscle free histidine were reduced by >25% FM replacement. Muscle free lysine was only reduced by 75% FM replacement. Replacement of FM reduced EAA peak concentrations and resulted in slower release of EAAs in serum. Cumulative total EAAs in serum and muscle decreased with FM replacement. Ratios of EAAs to lysine showed that tryptophan was the most limiting EAA. However, isoleucine, leucine, methionine and phenylalanine were also inadequate for muscle synthesis for the first 9–12 hr following force‐feeding. Optimal time for protein synthesis was ≥36 hr. Although any level of FM replacement did not reduce protein ADCs and trypsin activity, replacement of ≥25% FM reduced EAA ADCs and bioavailability of lysine and histidine, which partly contributed to the observed differences in growth.     

Total fish meal replacement with rapeseed protein concentrate in diets fed to rainbow trout (Oncorhynchus mykiss Walbaum)

The potential of rapeseed protein concentrate as fish meal alternative in diets for rainbow trout (initial average weight 37.8?±?1.4?g) was evaluated. Nine experimental tanks of a freshwater flow-through system were stocked with 12 fish each. Triplicate groups of fish received isonitrogenous (47.9?±?0.5% CP) and isoenergetic (22.4?±?0.2?kJ?g^?1) experimental diets with 0, 66 and 100% of fish meal substituted with rapeseed protein concentrate (71.2% CP), thereby providing 0, 29 and 43% of dietary protein. As the amino acid profile of rapeseed protein concentrate was comparable to fish meal, there was no need to supplement experimental diets with synthetic amino acids. At the end of the 84?days of feeding period, fish growth performance, feed intake and feed efficiencies were not compromised, when 100% of fish meal in the control diet was replaced with rapeseed protein concentrate, revealing a SGR of 1.19 or 1.10, a FCR of 1.09 or 1.18 and a feed intake of 78.5 or 74.7?g in fish fed on the control diet or fed the diet devoid of fish meal, respectively. Intestinal morphology did not reveal any histological abnormalities in all dietary groups. Blood parameters including haematocrit and haemoglobin as well as glucose, triglycerides and total protein in the plasma were not different between treatment groups. Thus, the rapeseed protein concentrate tested here has great potential as an alternative to fish meal in rainbow trout diets.     

Effect of substituting fishmeal with corn protein concentrate on growth performance,nutrient utilization and skin coloration in red hybrid tilapia,Oreochromis sp.

The objective of this study was to evaluate the effects of fishmeal (FM) replacement with corn protein concentrate (CPC) on growth performance, nutrient utilization, gut morphology and skin coloration of red hybrid tilapia, Oreochromis sp. Five isonitrogenous (350 g/kg crude protein) and isolipidic (10 g/kg lipid) diets were formulated to contain CPC that substituted 0%, 25%, 50%, 75% or 100% FM. Diets were fed to triplicate groups of tilapia (mean initial weight, 10.33 ± 0.02 g) twice daily for 63 days. The results showed that replacing up to 50% FM in red hybrid tilapia diet with CPC did not show any significant adverse effects on growth, feed utilization, haematocrit counts, condition factor and gut morphology of tilapia (p > 0.05). However, replacing 75% or 100% FM with CPC had deleterious effects (p < 0.05). Carotenoids in CPC contributed to skin yellowness, which was significantly higher in the diet where 100% FM was replaced with CPC. Using regression analysis, the optimal substitution level of FM by CPC was estimated at 25% for percentage weight gain, 33% for FCR and 29% for protein efficiency ratio. CPC could be used as a single plant protein source to substitute up to 50% FM in red hybrid tilapia diets.     

Replacement of fish meal by potato protein concentrate in diets for rainbow trout, Oncorhynchus mykiss (Walbaum): growth, feed utilization and body composition

Five experimental diets (PPC1, PPC2, PPC3, PPC4 and PPC5) containing about 465 g kg⁻¹ crude protein were formulated to contain graded levels of potato protein concentrate (PPC) (a by-product of potato starch manufacturing) by replacement of fish meal protein. The contents of PPC were 0, 94, 200, 304 and 510 g kg⁻¹ respectively. The diets were prepared isonitrogenously and isocalorically. A 6-week growth trial was conducted with rainbow trout, Oncorhynchus mykiss (Walbaum), at about 14°C to evaluate the potential use of the potato protein concentrate in trout diets.
The results showed that fish fed diets containing PPC showed decreased growth, feed utilization and condition factor, and increased mortality when PPC constituted the sole protein source. Incorporation of PPC in the diets resulted in decreased dry matter, protein and fat and increased ash contents of the fish body. In conclusion, the type of potato protein concentrate used, especially at high levels, was not suitable as an ingredient in trout feed.     

Dietary essential amino acids and heat increment in rainbow trout (Oncorhynchus mykiss)

Oxygen consumption attributable to apparent heat increment (AHI) was measured in relation to varying essential amino acid proportions (EAA) infused into rainbow trout,Oncorhynchus mykiss (250–450 g), induced to swim at 1 BL s^–1. Five diets, mimicking EAA concentrations in trout whole body protein, deficient in the branched chain amino acids (isoleucine, leucine and valine), containing unbalanced proportions of EAAs and supplying lysine in excessive and limiting proportions, were tested. Following infusion of the experimental diets, a significant increase in oxygen consumption was observed. Changes in plasma EAAs following infusion paralleled the time course of AHI (i.e., oxygen consumption). AHI represented the equivalent of 15–32% of the gross energy intake depending on dietary EAA composition. Diets supplying EAAs similar to trout whole body protein and limiting in lysine produced the lowest AHI values, indicating efficient utilization of dietary amino acids. Higher AHI values were associated with diets deficient in the branched chain amino acids and diets supplying lysine in excess. Duration of elevated metabolism was independent of both dietary composition and energy intake. Different proportions of EAAs in the diet can increase the energy expended as AHI. In an attempt to reduce the energy liberated as AHI, attention must be paid to the quality, quantity and balance of dietary EAAs.     

Total fish meal replacement with canola protein isolate in diets fed to rainbow trout (Oncorhynchus mykiss W.)

The potential of canola protein isolate (CPI) as fish meal alternative in diets for rainbow trout was evaluated. Apparent digestibility coefficients (ADCs) for protein from a fish meal‐based reference diet (89.2 ± 1.1%) and CPI (84.6 ± 1.8%) were determined by indirect marker method in a digestibility experiment. ADC of dietary dry matter was slightly lower for the reference diet (62.5 ± 4.7%), but not significantly different to the CPI test diet (65.9 ± 3.1%). In a subsequent growth trial, 20 fish (initial weight 31.5 ± 0.5 g) were stocked into each of 15 experimental tanks of a freshwater flow‐through system. Fish were organized in triplicate groups and received experimental diets with 0%, 25%, 50%, 75% and 100% of fish meal replaced with CPI on the basis of digestible protein (designated as Control, I25, I50, I75, I100 respectively). At the end of a 70‐day feeding period, growth performance, feed intake and feed conversion ratio of treatment groups receiving diets I25, I50 or I100 were similar to the control group, while fish fed diet I75 showed significantly higher weight gain caused by improved feed conversion. The tested CPI was therefore identified to be a highly valuable fish meal alternative, not negatively affecting diet palatability, feed intake and feed efficiencies.     

Growth performance,haematological and serum biochemical profiles in rainbow trout (Oncorhynchus mykiss) fed diets with varying levels of lupin (Lupinus albus) meal

A feeding experiment was conducted to study the response of rainbow trout juveniles fed different levels of lupin meal in diets for rainbow trout juveniles. Very limited information is available on the relationship between dietary lupin meal in rainbow trout health status. Therefore, this study aimed to determine the effects of lupin meal inclusion levels (0%, 15%, 30%, 45%, and 60%) on growth performance and health status of rainbow trout juveniles. The experimental diets (LM₀, LM₁₅, LM₃₀, LM₄₅, and LM₆₀) were formulated iso‐nitrogenous (41% crude protein) and iso‐calorific (18% crude lipid). The fish were fed twice a day. As a result, the best growth performance was observed in fish fed with LM₁₅ and LM₃₀ diets. No significant differences were detected among experimental groups in terms of body compositions. The haematological values showed significantly (p < 0.05) lower heamatocrit and mean cellular volume (MCV) in the group of LM₆₀ compared with the other groups. For the other haematological parameters such as haemoglobin, red blood cell and mean cellular haemoglobin studied in the present study no significant differences were observed (p < 0.05). The lupin meal included groups showed significant reduction in total protein (TPROT), triglyceride (TROG), cholesterol (CHOL), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) compared with the control group (p < 0.05). The inclusion of lupin meal did not cause any changes in glucose (GLU), glutamic oxaloacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) between the treatment groups (p < 0.05). In conclusion, lupin meal might be used in rainbow trout diets up to 30% without any malnutrition effect on growth performance, haemotological and serum biochemical parameters.     

Dynamics of plasma free amino acids in rainbow trout (Oncorhynchus mykiss under variety of dietary conditions

Plasma amino acid profiles in the systemic circulation of rainbow trout acclimated to diets containing different protein sources, with and without supplementation with free amino acids, were monitored for up to 120 hours after consumption of the diets. Plasma concentrations of lysine, methionine, and isoleucine increased more rapidly after feeding a diet supplemented with these amino acids in free form and, depending upon the increase in plasma concentration, remained at concentrations above those in fish fed the basal diet for at least 24h after feeding. Dietary supplementation with isoleucine increased plasma concentrations of leucine and valine as well as of isoleucine. Maximum plasma concentrations for most amino acids were attained between 12 and 24h postprandial. Dietary inclusion of gelatin caused more rapid elevations in plasma glycine and serine than did free glycine. Feeding at three hour intervals resulted in stable plasma concentrations of individual amino acids in contrast to the fluctuations occurring when fish were fed once daily. Frequent feeding favoured a higher proportion of protein to lipid in body composition.     

Determination of growth performance,meat quality and colour attributes of large rainbow trout (Oncorhynchus mykiss) in the southern Black Sea coasts of Turkey

The aim of this study was to determine the growth performance, meat quality and colour attributes of large rainbow trout (Oncorhynchus mykiss) in net cage systems in the southern Black Sea coasts of Turkey. In the study, large rainbow trout with an initial weight of 1,322.07 ± 57.72 g were reached to 3,385.30 ± 140.98 g and the survival rates were 95.69 ± 1.32% in 5‐month production period. Crude protein and crude fat values of fish meat were ranged between 16.75 ± 0.07–20.18 ± 0.90% and 9.22 ± 0.15–12.29 ± 0.42%, respectively (p < .05). The essential and non‐essential amino acid values were between 12.92 ± 0.02–13.09 ± 0.01 g/100 g and 11.97 ± 0.14–11.47 ± 0.01 g/100 g, respectively (p > .05). C20:5n‐3, C22:6n‐3, ?3 and ?6 values in fish meat were between 4.32 ± 0.02–4.30 ± 0.08% (p < .05), 8.31 ± 0.10–7.72 ± 0.15% (p < .05), 13.41 ± 0.10–12.93 ± 0.23% (p < .05) and 21.85 ± 0.06%‐19.74 ± 0.36 (p < .05), respectively. As a result, it can be concluded that large rainbow trout cultured in the southern Black Sea coasts of Turkey is a rich source of food in terms of fatty and amino acid compositions and atherogenicity index, thrombogenicity index and hypocholesterolaemic/hypercholesterolaemic values.     

Partial replacement of soybean meal with Methylobacterium extorquens single‐cell protein in feeds for rainbow trout (Oncorhynchus mykiss Walbaum)

A feeding trial was conducted with juvenile rainbow trout (15–16 g initial weight) to assess the effects of including single‐cell protein (SCP) produced from Methylobacterium extorquens in trout feeds. Three isonitrogenous and isoenergetic diets were produced: a control diet and two experimental diets containing 5% or 10% bacterial protein meal replacing soybean meal. Triplicate tanks, each containing 35 fish, were fed each diet to apparent satiation in a constant‐temperature (15°C), flow‐through tank system for 12 weeks. No statistically significant differences in final fish weight or other fish growth parameters were observed. Similarly, feed efficiency parameters showed no significant differences among groups. Nutrient retention indices (protein, fat, energy) were relatively high and similar among fish in each dietary treatment group, as were whole body proximate compositions. Fish survival was high, with a small but statistically significant increase for the 10% SCP diet. Overall, results demonstrate that SCP from M. extorquens is a safe and effective alternative protein for rainbow trout diets at the low inclusion levels tested. Slightly lower weight gain in fish fed the 10% SCP diet was largely due to lower feed intake, suggesting that adding palatability‐enhancing ingredients to feeds may allow higher levels of M. extorquens SCP to be used without compromising fish growth.     

Arginine effects on biochemical composition of sperm in rainbow trout,Oncorhynchus mykiss

The present study investigated the effect of arginine on seminal plasma composition in rainbow trout. Male rainbow trout broodstocks (2500 ± 200 g) were fed five practical diets (each consisting of three triplicates) supplemented with Arginine at 0.50%, 1.50% and 2.00%. The control group were fed without arginine. Broodstock feeding lasted for 90 days, and then fish semen was sampled. Results indicated no significant differences in LDH, ALP, Fe²⁺ and phosphorous content among the different treatments. The lowest levels of AST and ALT and the highest levels of Ca²⁺ and Mg²⁺ ions were observed in the treatment fed with 1.50% arginine, which showed significant differences from other treatments (P < 0.05). Moreover, the amount of Cl^?, Na⁺ and K⁺ ions was significantly increased in the seminal plasma in fish fed diets containing arginine in comparison with the control. As the amount of arginine was increased, the levels of uric acid became significantly greater in contrast to urea and glucose levels. The highest amounts of cholesterol, fructose and total protein were observed in treatments fed on 2.00%, 0.50% and 1.00% arginine, respectively, showing significant differences from other treatments (P < 0.05). The highest pH value was assayed in the 1.50% arginine treatment. Results indicated that arginine had a potential efficacy on semen quality in rainbow trout broodstocks.     

Apparent absorption efficiencies of amino acids in rainbow trout, Oncorhynchus mykiss (Walbaum), fed diets containing bacterial single-cell protein

The aim of the present study was to compare the apparent absorption efficiency of individual indispensable and dispensable amino acids in diets containing varying proportions of bacterial single cell protein (BSCP) and fishmeal when fed to rainbow trout, Oncorhynchus mykiss (Walbaum). Four diets were formulated to contain a total of 45.8% crude protein, of which 0% was from BSCP in diet 1 (BSCP-0), 25% in diet 2 (BSCP-25), 62.5% in diet 3 (BSCP-62.5) and 100% in diet 4 (BSCP-100); the remainder of the protein was from fishmeal. The four diets were isonitrogenous and had similar amino acid compositions. Duplicate groups of 25 fish were fed one of the four experimental diets at the rate of 20 g kg^?1 body weight per day for 132 days. Apparent absorption efficiency was measured over a 45-day period during the growth trial. Results from two methods of faeces collection and two indicators of absorption efficiency were compared. The amino acid absorption efficiency of BSCP-100 was significantly lower (P < 0.05) when compared to the other three diets and absorption of some of indispensable amino acids was below the requirement level. The variation seen in individual amino acids absorption efficiencies between diets suggests that this parameter may be important in fish nutritional investigations.     

Nutritional,physiological and haematological responses in rainbow trout (Oncorhynchus mykiss) juveniles fed detoxified Jatropha curcas kernel meal

Jatropha curcas is a multipurpose and drought‐resistant tree, widespread throughout tropics and subtropics. Its seeds are rich in oil and protein. It is being promoted as a biofuel plant. Jatropha kernel meal obtained after oil extraction is an excellent source of protein [580–660 g kg^?1 crude protein (CP)]. However, the presence of toxic and antinutritional constituents restricts its use in fish feed. Jatropha kernel meal was detoxified. Using Oncorhynchus mykiss juveniles, a 12‐week experiment was conducted to evaluate the nutritional quality of detoxified Jatropha kernel meal (DJKM). Oncorhynchus mykiss juveniles (36, av. wt. 4.2 ± 0.4 g) were distributed into three groups with 12 replicates and fed isonitrogenous (CP 450 g kg^?1) diets: control [fish meal (FM)–based protein], J₅₀ and J_62.5 (50% and 62.5% of fishmeal protein replaced by DJKM). Growth performance, apparent lipid conversion, hepatosomatic index, nutrients and energy digestibilities; efficiency of digestible nutrients and energy; and glucose and creatinine levels in blood were statistically similar (P > 0.05) for control and J₅₀ but were higher (P < 0.05) than for J_62.5. Opposite trend was observed for phosphorus, sodium, albumin and total protein in blood. Feed conversion ratio, protein efficiency ratio, protein productive value, energy retention, gastro somatic index, muscle lipid peroxide; and red and white blood cells, haematocrit, haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration; alkaline phosphatase and alanine transaminases activity, globulin, total bilirubin, blood urea nitrogen, calcium and potassium in blood and lysozyme activity in serum did not differ significantly among the groups. Intestinal enzyme activities; and plasma and muscle cholesterol levels for control were higher (P < 0.05) than for DJKM groups, while opposite trend was observed for relative intestinal length (mm g^?1). Conclusively, performance of J₅₀ group was similar to control group and, thus, is recommended as the optimal diet for rainbow trout.     

Partial replacement of fishmeal with corn gluten meal,pea protein isolate and their mixture in diet of black sea bream (Acanthopagrus schlegelii) juveniles: Effects on growth performance,feed utilization and haematological parameters

Corn gluten meal (CGM), pea protein isolate (PPI) and their mixture (CPP, 1:1 ratio) were evaluated as fishmeal (FM) alternatives in black sea bream (Acanthopagrus schlegelii) juveniles (9.02 ± 0.12 g). A FM diet was designed as control, and other six diets had 20% and 40% FM protein replaced by CGM, PPI and CPP, respectively, with the supplementation of crystalline methionine, arginine and lysine. After the 8‐week feeding trial, significantly lower weight gain was found in fish fed the 40% CGM diet (p < .05), whereas other treatments had no statistical difference (p > .05). The values of feed efficiency ratio and feed intake, as well as proximate compositions of muscle and whole body, were not significantly influenced in all treatments. Apparent digestibility coefficients (ADCs) of dry matter, crude protein, threonine, valine, methionine, isoleucine, leucine, phenylalanine and lysine were significantly influenced by protein source. Fish fed the 40% CGM diet had significantly higher content of essential amino acid in muscle than that of the 20% PPI diet. Fish fed the 40% CGM diet had significantly lower content of serum cholesterol than other treatments (p < .05). Elevated serum superoxide dismutase activity was found in fish fed the 40% plant protein diets. In conclusion, between 20% and 40% FM protein could be replaced by CGM, while about 40% FM protein derived from PPI and CPP could be applied in black sea bream.     

Supplementing rainbow trout (Oncorhynchus mykiss) broodstock diets with choline and methionine improves growth in offspring

Nutritional programming represents the mechanism through which broodstock feeding strategies have lifelong effects on the offspring generation. The objective of this study was to determine whether supplementing rainbow trout, Oncorhynchus mykiss broodstock diets with choline and methionine affects offspring growth performance. Experimental diets were produced by top-dressing a commercial broodstock diet with (a) 12,000 ppm methionine, (b) 7,400 ppm choline, (c) 12,000 ppm methionine and 7,400 ppm choline, or (d) water (control). Six rainbow trout families were fed experimental diets beginning 18 months post-hatch through spawning; the offspring consumed a commercial diet. The broodstock diet did not affect maternal body weight, body condition, egg size, or egg yield (p > .05). Eggs from choline-treated broodstock contained 10% more choline than control eggs (p < .05). Offspring from choline-treated broodstock were smaller than controls at 146 days post-hatch (dph) (p < .05). At the final harvest (439 dph), offspring from the control broodstock weighed 12–18% less than offspring from broodstock consuming the supplemented diets (p < .05). However, there was a significant diet-by-family interaction on offspring growth (p < .05); supplemented diets improved performance in three of the six broodstock families. These findings indicate that supplementing broodstock diets with methionine and choline causes a nutritional programming effect that benefits growth in offspring.     

Effects of arginine supplementation on growth performance and plasma arginine,ornithine and citrulline dynamics of rainbow trout,Oncorhynchus mykiss

This study aimed to re‐evaluate the effect of excessive arginine supplementation on growth and feed efficiency of rainbow trout, and to assess the effect of dietary arginine supplementation on hepatic amino acid composition, expression of arginase Ⅱ (ARG 2), inducible nitric oxide synthase (iNOS), and heat shock protein 70 (HSP70) genes in the intestine, and plasma arginine, ornithine, citrulline and urea levels at 0, 6, 12 and 18 hr‐postprandial. Rainbow trout (body weight: 60.5–65 g) were fed diets containing 1.47 (control [CTRL]), 3.89 (3.89A) and 5.64% (5.64A) arginine for nine weeks. Higher muscle protein content was observed in 3.89A than CTRL (p < 0.05). In postprandial study, plasma arginine of 5.64A kept increased until 12 hr‐postprandial and reached identical value (around 150 µg/ml) until 18 hr‐postprandial in 5.64A. Significant increase of plasma arginine level was only observed in arginine supplemented group. Meanwhile, plasma citrulline level in CTRL was significantly higher than in 5.64A at 18 hr‐postprandial. A significantly higher hepatic citrulline level was also observed in CTRL than in 5.64A (p < 0.05). Significantly higher plasma and hepatic free ornithine level was observed in 5.64A than CTRL while significantly higher expression of intestinal ARG2 and HSP70 was found in arginine supplemented groups. These results suggest that citrulline availability seems to be stimulated by arginine deficiency in the CTRL and the presence of arginase in the intestine to regulate excess dietary arginine.     

Digestibility and growth performance of juvenile rainbow trout (Oncorhynchus mykiss) fed with pea and canola products

A digestibility experiment and subsequent 84-day feeding experiment evaluated the use of pea and canola meal products in diets for rainbow trout. The effect of milling and heat treatment on nutrient, dry matter and energy digestibility of raw/whole peas, raw/dehulled peas, extruded/dehulled peas and autoclaved air-classified pea protein was determined. Digestibility of the protein component was uniformly high for all pea ingredients (90.9–94.6%), regardless of the processing treatment. Autoclaving or extrusion increased starch digestibility by 41–75% ( P  ≤ 0.05), which consequently increased energy and dry matter digestibility of whole and dehulled peas. Autoclaved air-classified pea protein had superior protein (94.6%), energy (87.0%) and dry matter (84.0%) digestibility ( P  ≤ 0.05). It was demonstrated that inclusion of 25% dehulled peas, 20% air-classified pea protein or 20% canola meal fines was feasible in trout diets allowing for replacement of soya bean meal. The data showed no difference ( P  ≥ 0.05) in feed intake, final weight and specific growth rate (SGR) measurements, and feed utilization was not compromised with inclusion of pea or canola meal products as the primary plant ingredient. It was concluded that dehulled peas, air-classified pea protein and canola meal fines are suitable ingredients for use in trout diet formulation at a level of 20%.     

Partial replacement of fishmeal with sunflower cake and corn oil in diets for tilapia Oreochromis niloticus (Linn): effect on whole body fatty acids

The objective of this study was to determine the effect of replacing fishmeal with high‐fibre and low‐fibre sunflower cakes (HFSC and LFSC) on whole body fatty acid composition in tilapia Oreochromis niloticus (Linn). Sex‐reversed O. niloticus males with an initial weight of approximately 16g ± 0.95 (SD) were used. A control diet based on herring meal and soybean meal was formulated. Six test diets were formulated such that low‐fibre (LF) and high‐fibre (HF) sunflower cakes (SC) contributed 30%, 60% and 80% of the dietary protein, and the diets were designated as LFSC‐30, LFSC‐60, LFSC‐80, HFSC‐30, HFSC‐60, and HFSC‐80 respectively. All fish were held at 25–28°C. They were fed three times daily their prescribed experimental diets for 70 days. At the end of this period they were starved for 24 h and weighed. Five fish representing the average weight of each replicated group (n=3) were frozen in plastic bags at –22°C for determination of fatty acid composition. Fatty acids in the fish were significantly influenced by diet. Palmitic, oleic and linoleic acids were the most abundant fatty acids in both the diets and the fish. Linoleic acid (18:2 ω6) was the most abundant fatty acid in diets based on sunflower cake. The levels of this fatty acid were also higher in fish fed diets with high contents of the sunflower cakes (LFSC‐60, LFSC‐80 and HFSC‐80) (31.3%, 34.7% and 29.7% respectively) than fish fed the control diet (13.8%). Percentages of long chain polyunsaturated acids of the ω‐3 family viz., docosahexaenoic (22:6 ω3) and eicosapentaenoic (20:5 ω3) were low in the diets and in the fish bodies. Fish fed the control diet had a higher level of 22:6 ω3 than those fed the other diets. The possible implications of the preceding findings for human health will be discussed.