Partial Replacement Of Fish Oil Research Articles

The impact of varying EPA:DHA ratio on Atlantic salmon health and welfare

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are essential fatty acids (EFA) vital for Atlantic salmon health, growth performance, and product quality. Yet, DHA and especially EPA are in short supply as ingredients for aquafeeds. Whilst the role of EFA in salmonid nutrition has been well studied, clear guidelines for aquaculture nutrition practitioners are still missing. This article addresses this gap by testing different EPA:DHA ratios (0.15, 0.55, and 0.98) when these two EFA represent at least 10% of the total pool of fatty acids in aquafeeds. Grow-out trials revealed no differences in zootechnical performance between fish fed the different diets during the initial eight weeks before vaccination challenge, nor on the subsequent three weeks post-vaccination for fish truly vaccinated or sham vaccinated (used as control groups for each of the three diets tested). Nonetheless, the FCR of vaccinated fish was significantly higher than sham vaccinated conspecifics, but diet yielded no significant effect. The expression of most genes screened (e.g., Elongation Factor 1α (Elf-1α), Interleukin 10 (IL10), Interleukin 8 (IL8), Tumor Necrosis Factor (TNFα)) was not significantly affected by vaccination or diet, while Viperine and Mx genes were upregulated in sham vaccinated fish fed the experimental diet with an EPA:DHA ratio of 0.55. The fatty acid composition of head kidney was affected by diet, namely EPA, but not DHA. The fatty acid profile of white muscle was also significantly affected by diet, with contrasting results for EPA and DHA; EPA content was higher for fish fed diets with higher EPA:DHA ratios and DHA levels were significantly higher (peaking at 16% of the total pool of fatty acids) when fish were provided with the diet featuring the lowest EPA:DHA ratio (0.15). Interestingly, fish fed the diet with the highest EPA:DHA ratio showed a lower number of wounded fish at the end of the grow-out period post-vaccination. Despite the reduction was not statistically significant, given the severe impact of wounded fish on salmon farming productivity, our results indicate that the partial replacement of fish oil with algal oil in salmon feed contributed to achieving a balanced EPA:DHA ratio, an adequate profile of Omega-3 long chain polyunsaturated fatty acids and improved the overall health and welfare of fish. This approach creates the opportunity to increase the productivity of fish farming operations and foster a more sustainable growth of the aquaculture industry.

Effect of Feeding Acid Oils on European Seabass Fillet Lipid Composition, Oxidative Stability, Color, and Sensory Acceptance.

Acid oils (AO) are fat by-products of edible oil refining with a high energetic value, being an interesting option for a more sustainable aquaculture nutrition. This study was conducted to evaluate the effects of the partial replacement of fish oil (FO) in diets by two AO instead of crude vegetable oils on the lipid composition, lipid oxidation and quality of fresh European seabass fillets, and after their commercial refrigerated storage for 6 days. Fish were fed with five different diets, the added fat being FO (100%) or a blend of FO (25%) and another fat (75%): crude soybean oil (SO), soybean-sunflower acid oil (SAO), crude olive pomace oil (OPO), or olive pomace acid oil (OPAO). Fresh and refrigerated fillets were assessed for fatty acid profile, tocopherol (T) and tocotrienol (T3) composition, lipid oxidative stability, 2-thiobarbituric acid (TBA) value, volatile compound content, color, and sensory acceptance. Refrigerated storage did not affect T + T3 total content but increased secondary oxidation products (TBA values and volatile compound contents) in fillets from all diets. The FO substitution decreased EPA and DHA and increased T and T3 in fish fillets, but the recommended human daily intake of EPA plus DHA could still be covered with 100 g of fish fillets. Both a higher oxidative stability and a lower TBA value were found in SO, SAO, OPO, or OPAO fillets, obtaining the greatest oxidative stability in OPO and OPAO fillets. Sensory acceptance was not affected by the diet or the refrigerated storage, while the differences found in color parameters would not be perceived by the human eye. According to the oxidative stability and acceptability of flesh, SAO and OPAO are adequate replacements of FO as energy source in European seabass diets, which implies that these by-products can be upcycled, improving the environmental and economical sustainability of aquaculture production.

Fish oil replacement with vegetable oils in compound feeds for rainbow trout

The aim of the work was to study the effect of compound feeds with full or partial replacement of fish oil with vegetable oils on the composition of tissues and growth perfomance of rainbow trout. Method of chemical analyses was used for the estimation of nutritional value of the feed. To determine the fatty acid composition of the total lipids of feed and muscle tissue of trout, methyl esters of fatty acids were analyzed on a Crystal 5000.2 chromatograph. To assess the effect of compound feeds on fish, a number of fish-breeding and biological indicators were determined. The novelty of the study is associated with modeling the optimal ratio of fish oil, rapeseed and soybean oils in fish diets. As a result of the research, it was found that the highest growth rates and survival at lower feed costs were found in fish grown on diet without replacing fish oil and diet with a mixture of fish oil, rapeseed and soybean oils in a ratio of 4:6:5. Replacing fish oil with vegetable oils in feed recipes did not adversely affect the chemical composition of fish muscle tissue. Due to the elongation and desaturation processes occurring in the tissues of rainbow trout, the inclusion of rapeseed and soybean oils in the compound feed did not lead to a decrease in the amount of eicosapentaenoic and docosahexaenoic fatty acids. The practical significance of the work lies in obtaining new diets for compound feeds for valuable fish species, providing opportunities for effective cultivation of rainbow trout with specified quality characteristics.

Effect of cell disruption on apparent digestibility of macronutrients from Aurantiochytrium acetophilum in Salmo salar pre-smolts

Determining the nutrient digestibility of a new ingredient is considered the first step to evaluate its suitability for use in aquaculture feeds. Thraustochytrids are considered a promising alternative to the partial replacement of fish oil. These microorganisms have a high long-chain fatty acid content, mainly docosahexaenoic acid (22:6-n-3). In this study, the apparent digestibility coefficient (ADC) of macronutrients provided by the biomass of whole and disrupted cells of Aurantiochytrium acetophilum in diets for Atlantic salmon (Salmo salar) were evaluated. A total of 44 fish per tank (34.4 ± 0.5 g) were used; the fish were randomly assigned to fifteen 100-L tanks. The apparent nutrient digestibility of the two forms of A. acetophilum biomass (whole and disrupted cells) was calculated by comparison with a reference diet apparent nutrient digestibility and in two levels of combination (10 and 20%) with each ingredient to be tested. The fish were fed the reference diet and the test ingredient diets for 25 days. Fish faeces were collected using decantation columns and analyzed to determine the ADC of dry matter, protein, lipids and gross energy. Two-way factorial analysis of variance indicated that the digestibility of dry matter, lipids and energy were significantly affected (P < 0.05) by cell treatment, inclusion percentage and the interaction between both factors. Compared to the whole-cell format, the physical treatment applied to rupture the cell walls favoured the ADC of dry matter, energy and lipids in juvenile Atlantic salmon when 20% of the ingredient was incorporated. On the contrary, inclusion of whole-cell biomass at 20% contributed to a significant decrease (P < 0.05) in the ADC of all the nutrients evaluated. The results suggest that cellular disruption of biomass from thraustochytrid with hard cell walls such as A. acetophilum will be advisable before inclusion in a feed formula. This aspect should be specially considered in non-extruded feeds for fish.

Replacing fish oil with crude palm oil in the diet of larval hybrid lemon fin barb (Barbonymus gonionotus ♀ × Hypsibarbus wetmorei ♂)

Hybrid lemon fin barb is a novel carp species produced in Malaysia crossing lemon fin barb (Hypsibarbus wetmorei, ♂) and silver barb (Barbonymus gonionotus, ♀). As the delicious wild H. wetmorei is being overexploited, this new hybrid species is produced, filling the production gap in Malaysian aquaculture. The hybrid larvae in our previous study showed high tolerance to bacterial diseases and revealed the suitability of culturing hybrid lemon fin barb in the tropics. The effects of increasing dietary replacements level of fish oil (FO) with crude palm oil (CPO) were investigated for the larval stage of this fast-growing and delicious carp species. Three-day old hybrid larvae were randomly allocated to fifteen 5-L tanks stocked at the rate of 50 larvae L−1. Five micro diets containing 0%, 25%, 50%, 75% and 100% dietary substitution levels of FO with CPO levels were formulated. An extra replicate tank was maintained for each treatment for enzyme sampling at 4-day intervals. After 20 days of the feeding trial, dietary replacement of FO with CPO did not significantly affect (p > 0.05) survival and growth of hybrid lemon fin barb larvae. Dietary CPO reduced (p < 0.05) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in hybrid larval tissues. Partial replacement of FO with CPO in hybrid lemon fin barb diets showed no lipid vacuoles in the liver and gut during the challenge test against A. hydrophila. In conclusion, total replacement of FO with CPO is acceptable for the culture of hybrid lemon fin barb larvae; though considering the health status of larvae, 75% replacement of dietary FO with CPO would be more applicable. However, lipid metabolism seems low at the early larval period in larvae fed dietary CPO.

Partial substitution of fish oil for linseed oil enhances beneficial fatty acids from rumen biohydrogenation but reduces ruminal fermentation and digestibility in growing goats.

This study was performed to investigate effects of partial replacement of fish oil (FO) for linseed oil (LO) on digestibility, ruminal fermentation and biohydrogenation in growing goats. Experiment 1 was carried out in four growing male goats aged 6 months in a 4 × 4 Latin square design. Goats were fed a basal diet supplemented with 25 g/kg dry matter either LO alone or in combination with tuna FO. Treatments were developed by replacing FO for LO at ratios of 0, 5, 10 and 15 g/kg DM corresponding to FO-0, FO-5, FO-10 and FO-15, respectively. Experiment 2 was carried out in an in vitro incubation system including 12 fermenters with the same four treatments. Each fermenter consisted of 40 mL goat ruminal fluid, 160 mL warm buffer, 2 g mixed substrates, and 50 mg FO-0, FO-5, FO-10 or FO-15. Fish oil inclusion reduced (P < 0.05) digestibility and nitrogen retention in Experiment 1. Increasing doses of FO in the diet induced a strong drop (P < 0.001) in ruminal total volatile fatty acid (VFA) concentration and protozoa population at 3 h post incubation, but did not affect individual VFA proportions. Substitution of FO for LO decreased mean concentrations of C18:0 (P = 0.057), c-9,c-12 C18:2 and C18:3n-3 (P < 0.001), but increased (P < 0.001) C20:5n-3 and C22:6n-3. Feeding FO-10 enhanced formation of ruminal c-9,t-11 conjugated linoleic acid (CLA) concentration compared with FO-0. Overall, combined data suggest that to improve ruminal concentrations of C20:5n-3, C22:6n-3, and c-9,t-11 CLA for deposition in tissues or milk with minimal risk of affecting digestibility and ruminal fermentation, a dietary supplementation of 15 g/kg LO and 10 g/kg FO would be suitable.

Influence of Dietary Lipids and Environmental Salinity on the n-3 Long-Chain Polyunsaturated Fatty Acids Biosynthesis Capacity of the Marine Teleost Solea senegalensis

Fish vary in their ability to biosynthesise long-chain polyunsaturated fatty acids (LC-PUFA) depending upon the complement and function of key enzymes commonly known as fatty acyl desaturases and elongases. It has been reported in Solea senegalensis the existence of a Δ4 desaturase, enabling the biosynthesis of docosahexaenoic acid (DHA) from eicosapentaenoic acid (EPA), which can be modulated by the diet. The present study aims to evaluate the combined effects of the partial replacement of fish oil (FO) with vegetable oils and reduced environmental salinity in the fatty acid composition of relevant body compartments (muscle, hepatocytes and enterocytes), the enzymatic activity over α-linolenic acid (ALA) to form n-3 LC-PUFA through the incubation of isolated hepatocytes and enterocytes with [1-14C] 18:3 n-3, and the regulation of the S. senegalensis fads2 and elovl5 in the liver and intestine. The presence of radiolabelled products, including 18:4n-3, 20:4n-3 and EPA, provided compelling evidence that a complete pathway enabling the biosynthesis of EPA from ALA, establishing S. senegalensis, has at least one Fads2 with ∆6 activity. Dietary composition prevailed over salinity in regulating the expression of fads2, while salinity did so over dietary composition for elovl5. FO replacement enhanced the proportion of DHA in S. senegalensis muscle and the combination with 20 ppt salinity increased the amount of n-3 LC-PUFA in hepatocytes.

Influence of Parental Fatty Acid Desaturase 2 (fads2) Expression and Diet on Gilthead Seabream (Sparus aurata) Offspring fads2 Expression during Ontogenesis.

Simple SummaryThe present study was on the gene expression of a rate-limiting enzyme in long chain polyunsaturated fatty acids (LC-PUFAs), fatty acyl desaturase 2 (fads2), throughout the embryonic development of a gilthead sea bream. The results showed a maternal transfer of fads2 mRNA to the developing oocyte. The embryonic fads2 expression might start after the neurula stage. No effect was found in fads2 expression in developing eggs from broodstock fed with a diet rich in rapeseed oil or fish oil. The present study provides information on the change of LC-PUFA biosynthesis during embryogenesis.Previous studies have shown that it is possible to increase the ability of marine fish to produce long-chain polyunsaturated fatty acid from their 18C precursors by nutritional programming or using broodstock with a higher fatty acyl desaturase 2 (fads2) expression. However, those studies failed to show the effect of these interventions on the expression of the fads2 gene in the developing egg. Moreover, there were no studies on the temporal expression of the fads2 during ontogeny in the gilthead sea bream (Sparus aurata). In order to determine the changes in expression of fads2 during ontogeny, gilthead sea bream broodstock with a high (HRO) or low (LRO) fads2 expression fed a diet previously used for nutritional programming, or a fish oil-based diet (LFO) were allowed to spawn. The samples were taken at the stages of spawning, morula, high blastula, gastrula, neurula, heart beating, hatch and 3 day-old first exogenous feeding larvae to determine fads2 expression throughout embryonic development. The results showed the presence of fads2 mRNA in the just spawned egg, denoting the maternal mRNA transfer to the developing oocyte. Later, fads2 expression increased after the neurula, from heart beating until 3-day-old larvae, denoting the transition from maternal to embryonic gene expression. In addition, the eggs obtained from broodstock with high fads2 expression showed a high docosahexaenoic acid content, which correlated with the downregulation of the fads2 expression found in the developing embryo and larvae. Finally, feeding with the nutritional programming diet with the partial replacement of fish oil by rapeseed oil did not affect the long chain polyunsaturated fatty acid (LC-PUFA) contents nor fads2 expression in the gilthead sea bream developing eggs.

Partial replacement of fish oil with vegetal oils in commercial diets: The effect on the quality of gilthead seabream (Sparus aurata)

The long-term unsustainability of fish oil as a lipid source in aquaculture feeds has led to its progressive replacement with vegetable oils. Several studies have shown that this replacement results in a different fatty acid profile that is likely to compromise the healthy properties and quality of fish by reducing their n-3 HUFA content. In the present study, we evaluate the effect of partial replacement of fish oil with vegetable oils on the quality of the final product. Eighty-four gilthead seabream (Sparus aurata) were fed one of two different commercial diets for 19 weeks in triplicate (14 fish per tank). These diets contained either 100 % fish oil (FO diet) or a 75 % vegetable oil blend (VO diet) (50/50 mixture of soybean and rapeseed oil). After slaughter, physical-chemical analyses (Fatty Acids (FAs); flesh color; Water-Holding Capacity (WHC); pH; and Texture Profile Analysis (TPA)) and a sensory analysis were performed. Fish fed either diet displayed similar growth and feed conversion rates (SGR and FCR). The fish fed the VO diet showed an increase in muscular n-6 fatty acids, which resulted in a lower n-3/n-6 ratio. A lower presence of EPA and DHA fatty acids was also observed, although the total quantity of n-3 fatty acids was similar in both groups. With regard to fat quality, the Atherogenic Index (AI) was lower in the VO-diet group, while both groups presented a similar Thrombogenic Index (TI). The diet had some effect on quality parameters, but the changes were not very intense. The differences observed in the a* and b* chromatic parameters were not significant, but a greater and significant color saturation in the vegetable oil group was observed. No significant differences in pH and WHC were observed. Fish fed the vegetal oil diet also scored higher for hardness, springiness, gumminess and chewiness. In the sensory analysis no significant differences were observed between the two groups. The differences observed for both the fatty acid profile and the quality parameters do not appear to have any important implications in terms of either health or the sensory properties of gilthead seabream fed a vegetable oil diet.

Partial replacement of fish oil with terrestrial lipid blend and effects on growth performance, body composition, immune parameter and growth‐related genes in yellow drum ( Nibea albiflora )

The imbalance of fish oil (FO) supply and demand has motivated efforts to identify an alternative for aqua feed. An 8-week feeding trial was conducted to evaluate the effects of dietary fish oil partial replacement with mixed oil from linseed and lard (1:1) on growth, body composition and immunity when the N3 long-chain polyunsaturated fatty acid (N3 LC-PUFAs) requirement is met for Nibea albiflora. Two types of experimental diets were formulated with 100% fish oil (FO) or 69% mixed oil (Mix). The results indicated that the Mix diet significantly improved the specific growth rate (SGR), weight gain (WG), feed efficiency ratio (FER), muscle tissue growth hormone receptor (GHR), insulin-like growth factor 1 (IGF1) and insulin-like growth factor 1 receptor (IGF1R) gene expression of the yellow drum (p < .05). No significant difference in the survival rate (SR), feed intake (FI), hepatosomatic index (HSI), viscerosomatic index (VSI), condition factor (CF), N3 PUFA percentage, liver antioxidant enzyme activities or pro-inflammatory gene expression was observed between the two treatments. Therefore, terrestrial blend lipid from linseed and lard could be used as an alternative for dietary fish oil without compromising growth performance and immunity for the juvenile yellow drum.

Aurantiochytrium sp. meal can replace fish oil in practical diets for the juvenile Pacific white shrimp

This study evaluated the use of microalgae (Aurantiochytrium sp.) meal as a substitute for fish oil in the diet of juvenile Pacific white shrimp (Litopenaeus vannamei) reared in a clear-water system. Dietary treatments at five replacement levels (0%, 25%, 50%, 75%, 100%) were performed in triplicate. After 46 days, only a slight difference in shrimp final weight was observed among treatments (0.61 g). An increase in final weight was observed with replacement of up to 50% fish oil for microalgae meal, while the optimal percentage of replacement estimated was 44.7%. Feed conversion rate (FCR) of animals fed a diet of Aurantiochytrium sp.meal to replace up to 50% fish oil decreased, and the optimal percentage of replacement estimated was 49.3%. The fatty acids profile in shrimp muscle tissue demonstrated an increase in docosahexaenoic acid (DHA) from 10.03% to 14.28% with increased replacement of fish oil by microalgae meal in the diet. Therefore, the partial replacement of fish oil by microalgae meal resulted in improved shrimp growth and FCR, and total replacement of dietary fish oil had no negative effects on these parameters. In addition, inclusion of microalgae meal raises the level of DHA in shrimp muscle.

Effects of Replacement of Fish Oil by a Mixture of Balanites aegyptiaca and Adansonia digitata Seed Oils on the Growth and Survival of Clarias anguillaris Fries (Linnaeus, 1758)

To investigate the effects of replacement of fish oil by a mixture of Balanites aegyptiaca and Adansonia digitata seed oils three isonitrogenous (35.36%) and isoenergetic diets (3.48 MJ / kg) were formulated for one kilogram (1kg). The study was carried out on fries Clarias anguillaris for six weeks.At the beginning of the experiment, 90 Clarias anguillaris of the initial average weight of 0.82 ± 0.055g were randomly divided into three different groups with two replicates containing 15 fish/each. Fish were kept in six plastic tanks (50 x 40 x 30 cm) container (50 L). The results showed that the substitution of fish oil by a mixture of Balanites aegyptiaca seed oil and Adansonia digitata seed oil gives growth for all diets. However, the best growths are obtained from all points of view (MWGr, MWGa and SGR) with diet A (mixture of Adansonia seed oil and Balanites seed oil at a ratio of 20 : 20) followed by the diet D (mixture of Adansonia seed oil and Balanites seed oil at 10 : 30) compare to the control diet M containing fish oil. The best FCR was observed with the diet A followed by the diet D compare to the FCR observed with the diet M. The PER was higher in diet A (0.57) followed by diet D with (0.45) that has no significant difference with the control diet M (0.43). The highest value 63% was obtained with the diet D followed by 60% with the diet M and finally the lowest value 53% was obtained with the diet A. In regards to the growth performance, fish fed a 100% vegetable oil diet showed the best growth performance. Therefore, the replacement of fish oil with a mixture of Balanites aegyptiaca seed oil and Adansonia digitata seed oil has no negative impact on the growth of Clarias anguillaris fry. It would be interesting first to study the inclusion rate of Balanites aegyptiaca seed oil for a partial replacement of fish oil.

Partial Replacement of Fish Oil in Tra Catfish (Pangasianodon hypophthalmus) Diet with Different Levels of LYSOFORTE™ Dry

Phospholipids are known to play a significant role in lipid transport in crustaceans. LYSOFORTE™ is a bio-emulsifier enriched with lysophospholipids used in animal feeds to improve the digestion and absorption of fat. Objective of the current study was to evaluate the growth promoting effect and fish oil sparing effect of LYSOFORTE™ Dry in Tra Catfish ( Pangasianodon hypophthalmus ) diets. This study comprised four treatment groups: positive control diet (T1) with 1% fish oil, negative control diet (with 1% less fish oil) (T2), negative control diet + LYSOFORTE™ Dry (0.05%) (T3) and negative control diet + LYSOFORTE™ Dry (0.10%) (T4). Each treatment group comprised 3 replicates with 50 juveniles/replicate. Negative control treatments with LYSOFORTE at 0.05% and 0.10% improved the average body weight gain by 16.08g and 25.74g (p&gt;0.05) with a corresponding FCR improvement of 1 point and 11 points respectively. Specific growth rate improved by 0.18%/day (0.05% LYSOFORTE™ Dry) and 0.28%/day (0.1% LYSOFORTE™ Dry). Survival percentage also improved in the negative control diets supplemented with LYSOFORTE™ Dry by 6.67%. Protein efficiency ratio increased by 0.22 (T3) and 0.11 (T4) whereas protein retention improved by 4.89% (T3) and 3.63% (T4) with respect to the negative control diet (T2). Lipid retention increased with the use of LYSOFORTE™ Dry: 27% for T3 and 37% for T4 (P&lt;0.05). Moreover, fish fed with negative control diet with 0.10% of LYSOFORTE™ Dry showed on par performance with those fed on the positive control diet. The results suggested the potential of formulating cat fish diets with less fish oil using LYSOFORTE™ Dry

Partial or total replacement of dietary fish oil with alternative lipid sources in silvery-black porgy (Sparidentex hasta)

An eight-week feeding trial was conducted to evaluate the effects of partial (50%) or total (100%) replacement of dietary fish oil with alternative lipid sources in silvery-black porgy. Seven isonitrogenous (50%) and isolipidic (20%) experimental diets were formulated namely: FO (fish oil), CO (canola oil), SO (sunflower oil), T (tallow), FC (fish oil+canola oil, 50:50), FS (fish oil+sunflower oil, 50:50) and FT (fish oil+tallow, 50:50). Fish fed the T and FT diets statically had lower final weight, weight gain and specific growth rate than other groups (P<0.05); Fish fed FT diet had the highest feed conversion ratio (P<0.05). Fish fed the CO and SO diets had the highest and the lowest whole body and muscle protein content, respectively (P<0.05). Fillet and liver n−9 monounsaturated fatty acids, n−6 and n−3 poly unsaturated fatty acids were highest in fish fed the CO, SO and FO, respectively (P<0.05). Apparent digestibility coefficient of protein and lipid, hemolytic and bactericidal activities were lowest in fish fed the T diet (P<0.05). From the above results, it is suggested that the vegetal oil sources are recommended for total and partial replacement of FO in silvery-black porgy diets, whereas tallow is not advisable as an alternative lipid source in this species. Statements of relevanceIt is essential to introduce alternative lipid sources, to meet increasing global demands of aquafeeds for the sustainability of aquaculture industry. Thus, the aim of present study was to provide insight into the possibility of the use of alternative lipid sources in diet for silvery-black porgy juveniles by evaluating the growth performance, feed utilization, body composition and hemato-immunological parameters.

Growth performance and quality traits of European sea bass (D. labrax) fed diets including increasing levels of freeze-dried Isochrysis sp. (T-ISO) biomass as a source of protein and n-3 long chain PUFA in partial substitution of fish derivatives

Abstract The aim of this study was to evaluate nutrient digestibility, growth performance, biometry, dressing out parameters, fillet muscle proximate and fatty acid composition of European sea bass ( Dicentrarchus labrax L.) of nearly marketable size, fed increasing levels of a freeze-dried biomass of Isochrysis sp. (clone T-ISO) as a partial substitute for protein and lipid from fish derivatives, in diets where the level of n-3 long chain (LC) PUFA were reduced through a partial replacement of fish oil for crude palm oil. Since diets including the test ingredients could possibly result in changes of certain quality attributes, fish were also subjected to overall sensory evaluation by a trained panel of assessors according to a triangle test. Three diets were formulated to be grossly iso -nitrogenous (N, 7.5% dry matter). A preparation in which fish meal/trimmings and fish oil were the major protein and lipid sources was used as a positive control diet. Two test complete diets were obtained from the control preparation so that approximately 10 and 20% crude protein from a high quality fish meal and 18 and 36% lipids from fish oil were supplied by the dried microalgae biomass. To stress the role of Isochrysis sp. as a source of n-3(LC)PUFA, the diets including increasing levels of the microalgae biomass were made grossly iso -caloric–lipidic by replacing a part of fish oil with palm oil which is known to be virtually free from n-3 PUFA. Each diet was fed to apparent satiety to quadruplicate groups of sea bass (142 g) over 121 days. The results have shown that replacing up to 20% crude protein from fish meal with a dried Isochrysis biomass and up to 36% fish lipid for those supplied by the microalgae in a diet with reduced level of fish oil, did not adversely affect feed intake or growth performance relative to controls even if the highest substitution rate resulted in a decline (P

Use of Plant Products as Candidate Fish Meal Substitutes: An Emerging Issue in Aquaculture Productions

The search for new dietary ingredients for total or partial replacement of fish oil has assumed a growing importance and is currently the subject of advanced scientific research. Plants are recognized to be a good source of both peptides and oils for fish aquafeeds. The present paper reviews the effects played on fish growth and physiology by some plant products, highlighting also their possible detrimental effects related to the presence of anti-nutritional factors. Although complete replacement of fish meal in feeds for cultured species is still difficult, the results obtained by the current studies performed on plant products are promising and encourage further research on this issue.

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.

English

An 80 day feeding trial was conducted to evaluate the effects of dietary inclusion of soybean oil to replace fish oil in the diet on growth, muscle fatty acids and immune responses of Pelteobagrus vachelli. Isonitrogenous and isocaloric diets were formulated with four fish oil to soybean oil ratios at 8:0 (FO, control), 6:2 (MO1), 2:6(MO2) and 0:8 (SO) in triplicate. Each diet was fed to juvenile darkbarbel catfish (1.0 ± 0.02 g) twice daily. No significant differences were found in weight gain, special growth rate, hepatosomatic index and intraperitoneal fat ratio among all the treatments. Incorporation of soybean oil significantly modified the fatty acid composition and n-3 and n-6 PUFAs ratio in muscle of fish. Fish fed MO1 showed significantly higher serum lysozyme activity, complement C3 and C4 contents and total IgM content than those fed other diets. These results indicate that partial replacement of fish oil with soybean oil does not compromise fish growth, but improve fish immunity. This study suggests that 25% fish oil replacement with soybean oil can be used in the practical diet of this fish. Key words: Darkbarbel catfish, Pelteobagrus vachelli, soybean oil, growth, fatty acid composition, immune responses.

Partial replacement of fish oil by flaxseed oil in Atlantic halibut (Hippoglossus hippoglossus L.) diets: effects on growth, nutritional and sensory quality

Three isonitrogenous (520 g protein kg−1 DM) and isoenergetic (25 MJ kg−1 DM) diets containing increasing levels of flaxseed oil (FxO; 0%, 40% and 70% of total added oil) at the expense of fish oil (FO) were tested for 33 weeks in groups of 61 individually PIT-tagged halibut (initial weight, 849 ± 99 g). Effects on fish growth performance, fillet nutritional and sensory quality were determined. Specific growth rate (0.2% day−1), feed conversion ratio (1.2–1.3) and nitrogen and energy retention were not affected by dietary treatments. Dietary fatty acid composition was reflected in fatty acid profiles of halibut muscle, liver and heart. Muscle of fish fed FxO diets contained higher 18:2n-6 and 18:3n-3 concentrations whereas 20:5n-3 and 22:6n-3 levels were significantly reduced. However, increasing FO replacement induced preferential retention of 22:6n-3 especially in heart, and a trend for 20:5n-3 conservation in heart and muscle was observed. FO replacement did not affect colour, texture and the characteristic fish odour and flavour of cooked fillets. By selectively retaining long-chain polyunsaturated fatty acids halibut can adapt to a lower dietary supply without adverse effects on growth, feed conversion ratio, survival, and fillet nutritional and sensory quality.

Effect of replacing dietary fish oil with soybean oil on production performance and fillet lipid and fatty acid composition of juvenile cobia Rachycentron canadum

As a marine carnivore exhibiting exceptionally high growth rates, cobia are considered a species for which fish oil (FO) replacement may be difficult. However, partial, if not complete, FO replacement is necessary to ensure sustainability. We evaluated the effects of graded substitution of dietary FO with soybean oil (SO) in cobia culture. Feeds contained FO (100% FO), SO (0% FO) or blends of the two (67% FO, 33% FO) as the supplemental lipid source. Production performance was largely unaffected by partial replacement of FO with SO: feed intake and final weight were reduced only in the 0% FO dietary treatment. Fillet total lipid fatty acid (FA) composition differed among the dietary treatments, closely approximating dietary FA profile. As increasing amounts of FO were replaced, SO-associated FA became enriched within the fillet lipid at the expense of FO-associated FA. Fillet lipid classes were associated with a particular FA signature, regardless of dietary FA profile. SO can replace a substantial amount of dietary FO; however, juvenile cobia appear to exhibit a nominal requirement for intact long-chain polyunsaturated FA. Therefore, aggressive FO replacement may result in essential fatty acid deficiencies unless the feeds can be amended with alternative sources of these essential nutrients.