Effect of dietary kefir on the growth performance,feed utilization and fatty acid profile of juvenile rainbow trout,Oncorhynchus mykiss

A study was conducted to determine the effect of feeding with diets containing kefir on growth performance and fatty acid profile of rainbow trout (Oncorhynchus mykiss). Four isonitrogenous (450 g protein kg^?1) and isocaloric (4325 kcal kg^?1) diets were prepared in trout feed to contain 0 (control), 20, 50 and 100 g kg^?1 kefir. Fish, initial weight of 46 g, were randomly distributed into triplicate 520‐L fibreglass tanks in freshwater flow‐through system. Fish were fed at 4% of the body weight thrice a day for 12 weeks. The results indicated that survival rate ranged from 97.14 to 100% without significant difference among treatments (p > .05). Whole‐body moisture and lipid composition were significantly affected by diets containing different levels of kefir (p < .05), but no differences were determined in protein and ash. Furthermore, the fatty acid profile of flesh showed differences among the groups. The percentages of saturated fatty acid in the flesh lipid decreased, while 18:3n‐3 and polyunsaturated fatty acids were increased at higher substitution levels of kefir grain. The present study showed that up to 100 g kg^?1 supplementation of kefir in diets could be improve the fatty acid profile, especially PUFA, in fish flesh without adverse effect on the growth, feed utilization and survival rate of rainbow trout.     

Effect of different plant oils on growth performance,fatty acid composition and flesh quality of rainbow trout (Oncorhynchus mykiss)

This experiment intended to assess the effect of sesame (SO), sunflower (SFO) and linseed (LO) oils on growth performance, fatty acid composition of fillet and liver or flesh quality traits of rainbow trout. Fish fed different four iso‐nitrogenous and iso‐lipidic experimental feeds. The control feed contained only fish oil as the primary lipid source. The fillet eicosapentaenoic acid and docosahexaenoic acid levels were the highest in fish fed control feed. In contrast, the liver eicosapentaenoic acid level was the highest in fish fed LO feed. Fish fed SFO feed had the highest level of total n?6 fatty acids in fillet and liver. Fish fed SO feed had the highest level of 18:1 n?9 fatty acid in fillet and liver. During the 12 days refrigerated storage period at 1°C, thiobarbituric acid (TBA) and pH values gradually increased in all dietary groups. However, trimethylamin nitrogen (TMA‐N) values increased in all dietary groups between days 0 and 9 during the storage period. Generally, pH value in fillets of control group was slightly higher than the other fish groups during 12 days refrigerated storage. Nevertheless, the chemical indicators of spoilage, TBA, TMA‐N and pH values were in the limit of acceptability for human consumption. Results of growth performance and chemical tests in the present study showed that sesame, linseed and sunflower oils could be used in feeds for rainbow trout. Moreover, we concluded that further researches should be carried out on the partial replacement of fish oil by sesame oil in rainbow trout nutrition.     

Effect of diets containing laurel seed oil on growth and fatty acid composition of rainbow trout,Oncorhynchus mykiss

The aim of this study was to determine the effects of replacing fish oil (FO) with laurel seed oil (LSO), as an alternative plant lipid source in diets on the growth and fatty acid composition of rainbow trout (Oncorhynchus mykiss; 111.47 ± 0.2 g mean individual weight). At the end of the feeding trial, survival was 100% in all treatments. No significant differences were seen in growth between the dietary groups (P > 0.05). The protein, lipid and ash contents were not significantly different among the groups (P > 0.05); however, there was a significant difference in protein and ash content between the treatment groups and the initial, and between the 50LSO group and the initial group, respectively (P < 0.05). The viscerosomatic index (VSI) and hepatosomatic index (HSI) values were not affected by increasing LSO percentages in the diets. The n‐6 polyunsaturated fatty acid (PUFA) concentration increased with increasing LSO levels in the diets. In contrast, the n‐3 PUFA levels decreased with increasing LSO levels in the diets. The liver and muscle were used for the analysis of fatty acids. The highest level of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) concentrations was recorded in fillet of fish fed the FO diet and the lowest in those fed the 50LSO diet. However, EPA and DHA ratios in the liver of fish fed the 75LSO diet were higher than those in fillet of fish fed the FO and 50LSO diets. No significant differences were seen in fatty acid composition between the dietary groups (P > 0.05). Based on the results of growth performance and fatty acid composition of the experimental fish in this study, it can be concluded that the 75% concentration of laurel seed oil performed best among the diets tested in the experiment.     

Effects of fish oil and partial fish meal substitution with oilseed oils and meals on growth performance, nutrient utilization and health of the rainbow trout Oncorhynchus mykiss

A feeding trial was conducted to investigate the effects of the replacement of dietary fish meal and fish oil with oilseed meals (soybean or canola) and canola oil on growth, nutrient utilization, body composition, diet digestibility and hematological parameters of rainbow trout Oncorhynchus mykiss. Seven diets were used; the control diet (designated FM) contained fish meal and fish oil as the main protein and lipid sources. For the experimental diets, 40% of fish meal protein was substituted with soybean meal, canola meal or a soybean/canola meal mixture, and these diets (designated SM, CM and SCM, respectively) contained fish oil as the lipid source. Three additional diets (SM?+?CO, CM?+?CO and SCM?+?CO) were formulated with the same vegetable protein meals but with fish oil replaced by canola oil. Fish were fed twice daily to apparent satiation for 11?weeks. The growth of fish fed the CM?+?CO diet was significantly lower than that of fish fed the FM, SCM, SM?+?CO and SCM?+?CO diets. The feed conversion ratio (FCR) was significantly better in fish fed the FM and SCM?+?CO diets than in fish fed the CM and CM?+?CO diets. Furthermore, feed intake was significantly lower for fish fed the CM?+?CO diet than in fish fed the SCM diet, and lipid digestibility of the CM?+?CO diet was significantly lower than that of all other diets. No significant differences of body composition were observed. Circulating leukocyte levels, leukocyte ratios and serum lysozyme activity remained unaffected by dietary treatment. However, it was observed that fish fed the CM?+?CO diet displayed hematocrit levels significantly lower (P?<?0.05) than that of fish fed the other diets. The results indicate that when diets contain either fish oil or canola oil, canola meal and soybean meal can be incorporated into rainbow trout feeds at a combined 32% inclusion level (replacing 40% of fish meal protein) without inducing significant negative effects on growth, nutrient utilization or health.     

The effects of Spirulina platensis meal on proximate composition,fatty acid profile and lipid peroxidation of rainbow trout (Oncorhynchus mykiss) muscle

This study evaluated the effects of diets containing 0, 25, 50, 75 and 100 g kg^?1 Spirulina platensis on proximate composition, fatty acid profile and lipid peroxidation of rainbow trout (Oncorhynchus mykiss). Supplementation of S. platensis did not change moisture and protein contents, but fish fed 50 and 100 g kg^?1 S. platensis had lower muscle lipid content than those fed control diet (P < 0.05). Fish fed 100 g kg^?1 of S. platensis contained lower percentages of saturated and monounsaturated fatty acid and a higher percentage of polyunsaturated fatty acid than those fed control diet (P < 0.05). The n‐3/n‐6 ratio of the fatty acid increased and muscle atherogenic and thrombogenic indices were significantly decreased as the dietary supplement of S. platensis increased. Furthermore, lipid peroxidation of the fillet significantly decreased with increasing dietary S. platensis at 4 °C and at ?20 °C (P < 0.05). The results of this study show that supplementation of S. platensis to the diet improves muscle quality of the rainbow trout.     

Effect of partial replacement of dietary fish meal by soybean meal with betaine attractant supplementation on growth performance and fatty acid profiles of juvenile rainbow trout (Oncorhynchus mykiss)

This study was conducted to investigate the effects of dietary incorporation of soybean meal for fish meal replacement and supplementation of betaine as an attractant on growth performance and fatty acid profiles of rainbow trout (Oncorhynchus mykiss). Juvenile trout were fed practical diets, with increasing soybean levels and betaine supplementations. The experimental diets consisted of a control diet with fish meal as the sole protein source (control) and no attractant, 25% soybean‐1% betaine diet (SBM25‐B1), 50% soybean‐2% betaine diet (SBM50‐B2), and 50% soybean‐0% betaine diet (SBM50‐B0). Average body weight was 12.69 ± 0.16 g at the beginning of experiments. Following 54 days feeding programme with experimental diets, average body weights reached 47.45 ± 1.22 g, 58.11 ± 1.77 g, 56.34 ± 1.87 g and 53.76 ± 1.74 g in the control, SBM25‐B1, SBM50‐B2 and SBM50‐B0 groups respectively. As compared with control treatment, significant differences were observed in weight gain, specific growth rate and feed intake of 1% betaine treatment at 25% soybean‐meal‐incorporated diet (p < .05), but no differences were observed in feed conversation ratio and survival rates (p > .05). Compared with the control treatment, betaine‐supplemented groups had significantly higher total saturated fatty acid contents (p < .05). On the other hand, the control treatment showed a significantly higher level of monounsaturated fatty acid than the betaine‐supplemented groups (p < .05). Significant differences were observed in fatty acid profile of 1% betaine‐supplemented group (p < .05) compared with the control. Present findings revealed that 1% betaine supplementation with dietary incorporation of soybean meal at 25% level positively influenced growth performance, feed utilization and fatty acid profiles of rainbow trout juveniles.     

Time of a single daily meal influences growth performance in rainbow trout, Oncorhynchus mykiss (Walbaum)

The effect of the time of delivery of a single daily meal was studied in immature rainbow trout, Oncorhynchus mykiss (Walbaum). In a first experiment, fish were fed 1.5 % of their body weight once a day at dawn. 1200 h, dusk or 2400 h and no attempt was made to monitor uneaten food. The best growth performance was observed for fish fed at dawn, while lowest performance was achieved by fish fed at 2400 h. During a second experiment, fish were fed at dawn or 2400 h at 0.9%, 1.2 % or 1.5% of their body weight, and the proportion of uneaten pellets was measured. Fish fed at 2400h showed lower growth performance, and feed intake was 10% lower than that of fish fed at dawn. Protein, lipid and energy retention (nutrient gain/ nutrient intake) was also the lowest in fish fed at 2400 h. These results lead to the conclusion that, in rainbow trout, feeding time has an effect on both feed intake and feed utilization.     

Effect of catch-and-release angling on growth and survival of rainbow trout, Oncorhynchus mykiss

Abstract Catch-and-release angling is popular in many parts of the world and plays an increasingly important role in fish conservation efforts. Although survival rates associated with catch-and-release angling are well documented for many species, sublethal effects have been less studied. An experiment was conducted to directly assess the effects of catch-and-release angling on growth and survival of rainbow trout, Oncorhynchus mykiss (Walbaum). Catch-and-release events were simulated in laboratory tanks maintained at 15–16 °C with hooks manually placed in pre-designated locations in the mouths of the fish. There were no differences in standard length ( P  = 0.59) or wet weight ( P  = 0.81) gained between caught and uncaught fish over a 1-month angling and recovery period. Survival was 96.99 ± 0.06% for rainbow trout caught and released, and did not vary with number (one, two or four) of captures. Thus, catch-and-release angling appears to have little effect on growth and mortality of rainbow trout hooked in the mouth.     

Evaluation of the influence of Lupinus angustifolius kernel meal on dietary nutrient and energy utilization efficiency by rainbow trout (Oncorhynchus mykiss)

This study examined the utilization efficiencies of three diets when fed to rainbow trout in a 28‐day growth study. Each of the diets was fed at one of three ration levels, and an additional starved treatment was also included. The diets differed by an increasing concentration of lupin (Lupinus angustifolius cv. Myallie) kernel meal (MKM) inclusion. Two lupin kernel meal inclusion levels of 15% (MKM15%) and 30% (MKM30%) were studied. The diets were formulated to equivalent digestible protein and energy specifications based upon the predetermined digestibility values for each of the ingredients used. There were no significant differences in digestible protein level among the diets. However, a significantly higher level of digestible energy of both MKM diets was measured, as well as a significantly higher level of digestible phosphorus in the MKM30% diet. No significant differences between the diets were observed with respect the utilization of dietary digestible energy. Over the full data range, the energy utilization efficiency was described by the linear equation of; y = 0.747x ? 26.174, R² = 0.985. Efficiency of protein utilization over lower digestible protein intake levels was also linear (y = 0.599x ? 0.142, R² = 0.905), but over the full range was better described by a nonlinear function. The comparison of the three diets in this study shows that the dietary inclusion of lupin kernel had no significant effect on the gain of either protein or lipid energy relative to protein or lipid energy intake, respectively. Protein energy use efficiency constants varied depending on the feed intake level, but were not significantly affected by diet type. The efficiency of use of lipid energy for lipid energy retention was also not affected by diet type. The findings of this study demonstrate that the inclusion of lupin kernel meal, at up to 30% of the diet, does not affect the ability of rainbow trout to utilize the dietary digestible protein and energy of diet in which it is included.     

Effect of dietary Spirulina platensis on fatty acid composition of rainbow trout (Oncorhynchus mykiss) fillet

This paper reports on inclusion of Spirulina platensis (SP) in rainbow trout (Oncorhynchus mykiss) fish diet and its effect on the fish tissue fatty acids (FAs) composition. Fish in triplicate groups with average initial body weight of 75 ± 0.23 g and age of about 7 months were fed a control diet with no supplements and with three experimental diets supplemented with 2.5, 5 and 7.5 weight percent (wt%) of SP for 12 weeks. At the end of experiment, the fillet FA compositions were evaluated. It was found that the composition of FAs in fish fillet was significantly (P < 0.05) affected by inclusion of SP in diets. As compared to the control sample, feeding the fish supplemented particularly with low levels of SP improved the quality of FAs by decreasing undesirable saturated FAs (SFAs) content from 20.03 to 17.93 % and increasing the level of some beneficial long-chain highly unsaturated FAs namely eicosapentaenoic acid (C20:5 n-3) from 6.47 to 7.27 %, docosapentaenoic acid (C22:5 n-3) from 1.42 to 1.56 % and docosahexaenoic acid (C22:6 n-3) from 1.26 to 1.35 %. Further increase in the SP inclusion level generally did not lead to desirable results. The SP inclusion in the fish diet had no significant impact on overall contents of n-3 and n-6 polyunsaturated FAs in fish fillet. However, the total highly unsaturated FAs (HUFAs) and n-3 HUFAs levels, UFAs/SFAs ratio and n-3/n-6 index were increased from 11.25, 10.65, 3.98 and 0.57 to 12.13, 11.56, 4.40 and 0.62 %, respectively, as a result of 5 wt% SP loading. In general, it can be concluded that SP inclusion up to 5 wt% of loading in rainbow trout culture can be beneficial in terms of FAs compositions of the fish fillet.     

Effect of dietary phytic acid and semi‐purified lignin on energy storage indices,growth performance,nutrient and energy partitioning of rainbow trout,Oncorhynchus mykiss

The effect of dietary phytic acid (PA) and semi‐purified lignin, and their interactions on growth performance, energy storage indices, nutrient deposition and partitioning in rainbow trout were studied in a 12‐week growth trial. Six isoproteic and isoenergetic diets were formulated differing only in their PA and lignin concentrations. In these diets, five essential amino acids: histidine, lysine, methionine (+ cysteine), threonine and tryptophan were formulated to be marginally adequate to the dietary requirement. Fish were pair‐fed with the amount of feed adjusted on a weekly basis. Among the performance indicators, dietary PA levels affected only the Fulton's body condition index (FCI) and whole carcass nitrogen retention efficiency (NRE; P < 0.05). On the contrary, lignin did not affect the whole carcass protein deposition (PD) and NRE but the lipid deposition (LD; P < 0.05), lipid retention efficiency (LRE; P < 0.01) and PD‐LD ratio (P < 0.05). Neither lignin nor phytic acid affected any parameters in dressed carcass and in viscera of rainbow trout except the visceral LD, which was affected only by the PA‐lignin interactions (P < 0.05).     

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.     

Effect of acute and chronic toxicity of paraquat on immune system and growth performance in rainbow trout,Oncorhynchus mykiss

In this study, the impact of paraquat (1, 1‐dimethyl 4, 4‐bipyridiniumdicholoride) on rainbow trout immune system and growth parameters was evaluated. In acute exposure, fish were distributed into four groups and exposed to 0, 54, 90 and 150 mg L^?1 of paraquat for 96 h. In chronic trial, fish were allocated into six groups and exposed to 0, 1.25, 2.5, 5, 10 and 20 mg L^?1 of paraquat for 30 days. Growth performance (percentage weight gain, condition factor and specific growth rate) and innate immune parameters (lysozyme, haemolytic complement activity and total immunoglobulin) were evaluated. Experimental data showed a LD₅₀ about 48.2 mg of paraquat per litre. Immunotoxic proprieties of paraquat especially in higher doses were shown in both trials. Total weight was also significantly decreased in chronic exposure when fish was subjected to 10 and 20 mg L^?1 paraquat whereas other growth parameters were not affected in this experiment. In general, these results suggest that paraquat exposure in rainbow trout could suppress the immunological and growth parameters.     

Availability of genetically modified soybean meal in rainbow trout Oncorhynchus mykiss diets

The use of genetically modified defatted soybean meal (GM SBM) as rainbow trout feed was investigated, in comparison with non-GM SBM. Both SBMs were included at levels of approximately 15 and 30% in four diets (42% protein). The diets were fed to juvenile fish (48.3 g average weight) for 12 weeks. The nutrient use showed that there was no significant difference in growth and feed performance between GM and non-GM SBM groups at both inclusion levels at the end of 12th week. The cauliflower mosaic virus 35S promoter fragment (220 bp) of the GM SBM was detected in the muscle of fish receiving both levels of GM SBM diet by nested PCR, but the frequency of detection was greater at the higher inclusion level. Additionally, the promoter fragment was not detected by the fifth day after changing the diet to non-GM. Conversely, the promoter fragment was not detected from fish fed with the non-GM SBM diet. The results demonstrated that the availability of protein in GM SBM was similar to that of non-GM SBM, and the promoter fragments found in the muscle of fish were not detectable after changing the diet to non-GM, verifying the availability of the GM SBM in rainbow trout feed.     

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.     

棉粕及脱毒棉粕替代鱼粉对虹鳟生长、体成分及血清生化指标的影响

用不同比例棉粕(CM)及FeSO4处理的脱毒棉粕(CM+Fe)替代饲料中0(CM0,对照组)、10%(CM10)、20%(CM20)、30%(CM30)、50%(CM50)、70%(CM70)和50%(CM50+Fe)、70%(CM70+Fe)的鱼粉,配置成8种等氮等能的饲料,喂养(9.79±0.13)g的虹鳟(Oncorhynchus mykiss)10周,每组设3个重复,研究棉粕及脱毒棉粕对虹鳟生长性能、体成分及血清生化指标的影响。结果显示:(1)对照组虹鳟增重率(WG)与CM10～CM50以及CM50+Fe组之间差异不显著,CM70组增重率、蛋白质效率(PER)与其他各组相比显著降低,饲料系数(FCR)显著升高。(2)各试验组虹鳟全鱼和肌肉粗蛋白、粗脂肪、粗灰分与对照组差异不显著;CM0～CM70组肌肉中游离棉酚含量也逐渐增加,CM50+Fe和CM70+Fe组肌肉游离棉酚含量显著低于CM50和CM70组。(3)CM70和CM70+Fe组谷丙转氨酶与谷草转氨酶活性与对照组相比显著升高,CM10～CM50和CM50+Fe组与对照组差异不显著,血清甘油三酯含量逐渐升高,血糖含量与总蛋白含量逐渐降低。结果表明,棉粕替代鱼粉的适宜比例为19.62%。     

The effect of ploidy on the fatty acid profile during the reproductive cycle of female rainbow trout (Oncorhynchus mykiss)

Rainbow trout Oncorhynchus mykiss triploids are regularly produced in fish farms to improve growth because the triploid females do not develop ovaries during the reproductive cycle. In this study, the tissue fatty acid allocations in triploid and diploid females were compared during the reproductive cycle to determine whether the ploidy influences the fatty acid profile of fish produced in aquaculture. The ovaries, liver, and white muscle fatty acid contents of diploid and triploid females were analyzed during the reproductive cycle. Diploid females tend to accumulate more polyunsaturated fatty acids than triploids during some phases of the reproductive cycle, and this profile was compensated by an increase in saturated and monounsaturated fatty acids in triploid females. Arachidonic acid (C20:4n6) was the main n6 polyunsaturated fatty acid in the ovaries of diploid females during the most advanced phases of the reproductive cycle, and docosahexaenoic acid (C22:6n3) was the main n3 polyunsaturated fatty acid. In triploid females, the percentage of both of these polyunsaturated fatty acids was lower than in diploid females during the most advanced phases of the reproductive cycle. In general, the lack of ovary development altered the hepatic synthesis of some fatty acids, mainly monounsaturated and polyunsaturated fatty acids, decreasing the content of the main fatty acids in the white muscle and, consequently, the mobilization of these specific fatty acids to the ovaries.     

Influence of dietary palm oil on growth, tissue fatty acid compositions, and fatty acid metabolism in liver and intestine in rainbow trout (Oncorhynchus mykiss)

This study aimed to investigate the effects of dietary crude palm oil (CPO) on fatty acid metabolism in liver and intestine of rainbow trout. Triplicate groups of rainbow trout for 10 weeks at 13 °C were fed on diets in which CPO replaced fish oil (FO) in a graded manner (0–100%). At the end of the trial, fatty acid compositions of flesh, liver and pyloric caeca were determined and highly unsaturated fatty acid (HUFA) synthesis and fatty acid oxidation were estimated in isolated hepatocytes and caecal enterocytes using [1‐¹⁴C]18:3n‐3 as substrate. Growth performance and feed efficiency were unaffected by dietary CPO. Fatty acid compositions of selected tissues reflected the dietary fatty acid composition with increasing CPO resulting in increased proportions of 18:1n‐9 and 18:2n‐6 and decreased proportions of n‐3HUFA, 20:5n‐3 and 22:6n‐3. Palmitic acid, 16:0, was also increased in flesh and pyloric caeca, but not in liver. The capacity of HUFA synthesis from 18:3n‐3 increased by up to threefold in both hepatocytes and enterocytes in response to graded increases in dietary CPO. In contrast, oxidation of 18:3n‐3 was unaffected by dietary CPO in hepatocytes and reduced by high levels of dietary CPO in enterocytes. The results of this study suggest that CPO can be used at least to partially replace FO in diets for rainbow trout in terms of permitting similar growth and feed conversion, and having no major detrimental effects on lipid and fatty acid metabolism, although flesh fatty acid compositions are significantly affected at an inclusion level above 50%, with n‐3HUFA reduced by up to 40%.     

Dietary fatty acid profiling in plant protein‐rich diets affects the reproductive performance,egg fatty acid profile and haematological parameters in female rainbow trout (Oncorhynchus mykiss)

The influence of dietary fish oil (FO) substitution with blends of vegetal oils (VO: canola, linseed, olive, sunflower, corn and coconut oils) in plant protein‐rich diets on reproductive performance and fatty acid dynamics of embryos was evaluated in female rainbow trout (Oncorhynchus mykiss) brooders (1.8 ± 0.1 kg). Four diets were formulated in which 20% (FO₈₀/VO₂₀), 50% (FO₅₀/VO₅₀), 75% (FO₂₅/VO₇₅) and 100% (VO₁₀₀) of FO were replaced by mixture of VO. The above‐mentioned diets were administered for a short period prior to spawning (3 months). Fish fed the VO₁₀₀ had the lowest fertilization rate (81.3 ± 2.3), whereas brooders fed the FO₈₀/VO₂₀ diet had the lowest survival rates at eyed embryo stage (83.7 ± 1.6%) and hatching rate (79.9 ± 3.1%). The fatty acid dynamics of embryos were not only affected by embryonic developmental stages, but also they were influenced by the dietary fatty acid profile. Our study confirmed that using blends of different VO sources and FM residual fat in the FO₂₅/VO₇₅ for the short‐term period prior to spawning seemed to be a good strategy in terms of successful reproduction for sparing high levels of FM and FO in diet of O. mykiss brooders.     

Effects of exercise-training on cardiac performance and muscle enzymes in rainbow trout,Oncorhynchus mykiss

Rainbow trout,Oncorhynchus mykiss, were exercise-trained for 18 hours per day over 28 days at water velocities up to 60% of their measured U_crit. Anin situ perfused heart preparation was used to compare maximum cardiac performance between control and trained fish. Trained fish had a larger stroke volume at a given filling pressure, as well as an 18% higher cardiac output and a 25% greater maximum power output. These observations indicate that exercise training in rainbow trout improved maximum cardiac performance. Adrenaline produced positive inotropic and chronotropic effects on the perfused heart, but exercise training did not alter these stimulatory effects. Maximal activities of citrate synthase (CS), B-hydroxyacyl CoA dehydrogenase (HOAD), glutamate dehydrogenase (GDH) and carnitine palmitoyl transferase (CPT) were measured in cardiac and skeletal muscles. CS, HOAD and GDH increased in red and white skeletal muscle as a result of training. Training also increased GDH activity in the endocardium and epicardium, and increased HOAD in the epicardium. While the training regime did not result in a statistically significant increase in U_crit and produced a decrease in the condition factor of the fish, other training effects were clearly evident. Furthermore, significant correlations were observed between U_crit and the maximal activities of GDH and HOAD.