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It is likely that Seriola spp. have nutritional requirements for long-chain polyunsaturated fatty acids (LC-PUFAs) and are unable to meet physiological demand for these nutrients via biotransformation of C 18 polyunsaturated fatty acids (C 18 PUFAs). However, it is unclear whether 20:4n-6 (arachidonic acid, ARA), 20:5n-3 (eicosapentaenoic acid, EPA), and 22:6n-3 (docosahexaenoic acid, DHA) are each required or, as in other fish, EPA is comparatively unimportant in maintaining performance of Seriola spp. Accordingly, we assessed growth performance and tissue fatty acid composition of juvenile California Yellowtail Seriola dorsalis (formerly Seriola lalandi ) fed a fish oil-based positive control diet (FISH), a soybean oil-based negative control diet (SOY), or experimental diets based on soybean oil supplemented with ARA, EPA, DHA, ARA and DHA, or all three of these fatty acids combined to achieve 50% or 100% of the concentrations typically observed in fish oil (SOY + 50% ARA, SOY + 100% ARA, SOY + 50% EPA, SOY + 100% EPA, SOY + 50% DHA, SOY + 100% DHA, SOY + 50% ARA and DHA, SOY + 100% ARA and DHA, SOY + 50% ALL, SOY + 100% ALL). As expected, fish fed the SOY diet exhibited significantly reduced growth relative to those fed the FISH diet. Supplementing with ARA alone had no effect on growth performance, and independent supplementation with EPA or DHA did not yield predictably positive effects on growth. However, fish fed the SOY + 100% ARA and DHA feed grew as well as those fed the FISH diet, and those raised on the SOY + 50% ALL and SOY + 100% ALL diets outperformed all others. Fatty acid composition of the fillet, liver, eye, and brain tissues was significantly affected by dietary treatment. As expected peripheral tissues were more modified than central tissues, and tissues of fish fed the soybean oil-based feeds exhibited higher levels of 18:2n-6 and lower levels of LC-PUFAs than those fed the rest of the experimental feeds. This effect was less overt among feeds supplemented with ARA and DHA or all three fatty acids. Results indicate that soybean oil can completely replace fish oil in California Yellowtail diets, assuming adequate levels of DHA and ARA are provided. Furthermore results illustrate the value of supplementing fish oil-free feeds with ARA, EPA, and DHA, but suggest that ARA and DHA are the primary drivers of LC-PUFA essentiality in this species. Statement of relevance The current manuscript provides valuable insights for fish nutritionists, for the aquafeed and aquaculture industries regarding fatty acid essentiality for marine carnivorous finfish. Our study supports the hypothesis that some LC-PUFAs are more physiologically important than others, with DHA and ARA being the primary drivers of fatty acid essentiality for juvenile California Yellowtail. [ABSTRACT FROM AUTHOR]

Replacing long-chain polyunsaturated fatty acid (LC-PUFA)-rich fish oil with alternative lipids in Florida Pompano Trachinotus carolinus feeds is likely to cause tissue LC-PUFA depletion in a manner similar to that observed in other species; however, there is little information available regarding fish oil sparing in this species. Moreover, it is unknown whether alternative lipids with different levels of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), or C 18 polyunsaturated fatty acids (C 18 PUFAs) are equally suitable in this context. Accordingly, we assessed the production performance and tissue composition of juvenile Florida Pompano (43.4 ± 0.2 g) fed diets containing menhaden fish oil (FISH) or 25:75 blends of fish oil and standard soybean oil (C 18 PUFA SOY), MUFA-enriched soybean oil (MUFA SOY), SFA-enriched soybean oil (SFA SOY), palm oil (PALM), or poultry fat (POULTRY). After 8 weeks, all diets were well accepted, and weight gain (228 ± 20%, grand mean ± SE) and specific growth rate (2.2 ± 0.1% body weight/day) were unaffected by dietary treatment. Feed conversion ratio, feed intake, and hepatosomatic index varied among treatments; however, the ranges of values observed were relatively narrow (FCR = 1.33–1.61, feed intake = 3.09–3.65% body weight/day, HSI = 1.1–1.5) and pairwise comparisons revealed few differences among treatments. Fatty acid profiles of the fillet, liver, and eye tissues generally mirrored dietary fatty acid composition, whereas the brain tissue was more resistant to dietary influence. Compared to those fed the FISH diet, fillets of fish fed the reduced fish oil diets had lower levels of n-3 fatty acids and LC-PUFAs, and greater levels of the fatty acids that were abundant in the alternative lipids. These trends were observed, albeit to a lesser extent in liver and eye tissues, but not in brain tissue, which was relatively resistant to diet-induced compositional change. In general, tissue fatty acid profile distortion was greatest among fish fed the MUFA SOY and C 18 PUFA SOY diets, least overt among fish fed the SFA SOY diet, and intermediate among fish fed the PALM and POULTRY diets. All alternative lipids appeared effective as partial substitutes for menhaden fish oil, but fully hydrogenated, SFA-rich soybean oil may offer some strategic advantage in terms of limiting diet-induced modification of tissue fatty acid profile in Florida Pompano. Statement of relevance As there are few studies addressing lipid nutrition of Trachinotus spp. and there is scarce information regarding the influence of different alternative lipid source on tissue levels of LC-PUFAs in these species, this study is relevant to aquafeed manufacturers and those culturing Florida Pompano and other Trachinotus spp. The present results provide valuable information regarding alternative lipids in marine carnivorous finfish feeds and their effects on fish performance and tissue fatty acid composition. Further, these findings highlight the promising potential of fully hydrogenated, SFA-rich soybean oil in aquafeeds. [ABSTRACT FROM AUTHOR]

Like other carnivorous species, White Seabass typically demand a nutrient-dense feed. Research is ongoing to develop formulations that contain minimal amounts of marine-origin protein and lipid, i.e., fish meal and fish oil, as a mean of reducing production costs and pressure on reduction fisheries. Previous research has shown that a greater level of fish oil-sparing is possible with saturated fatty acid-rich, hydrogenated soybean oil than with C 18 polyunsaturated fatty acid-rich standard soybean oil. To confirm this observation and to assess whether docosahexaenoic acid (DHA) is a limiting factor in fish oil sparing with soy-derived lipids, we evaluated the performance and tissue fatty composition of juvenile White Seabass fed diets containing fish oil, or standard or hydrogenated soybean oil with or without the addition of an algal DHA supplement. In addition, a low temperature stress challenge was done after the feeding trial. Fish fed the hydrogenated soybean oil feeds exhibited growth performance equivalent to those fed the fish oil feed, regardless of DHA supplementation. Growth performance was impaired among fish fed the standard soybean oil feed compared to those fed the fish oil control feed, but the addition of DHA corrected this effect. Dietary treatments significantly affected fatty acid composition of fillet, liver, eye, and brain tissues. In terms of long-chain polyunsaturated fatty acids and n-3 fatty acids, the tissues of fish fed the hydrogenated soybean oil feeds were equivalent to those of fish fed the fish oil feed. Tissues of fish fed the standard soybean oil feeds exhibited significantly lower levels of these beneficial fatty acids; however, this effect was corrected by dietary DHA supplementation. The low temperature stress challenge induced elevated plasma cortisol, and reduced glucose, osmolality and hematocrit; though dietary inclusion of soybean oils did not appear to negatively affect stress tolerance. Results suggest that fish oil sparing in White Seabass feeds is limited by DHA, and that DHA bioavailability may be greater in the presence of hydrogenated soybean oil than standard soybean oil. [ABSTRACT FROM AUTHOR]

Sparing marine-origin protein and lipid was investigated in diets for giant grouper ( Epinephelus lanceolatus ), using various combinations of soybean meal (SBM), soy protein concentrate (SPC), and an algal meal derived from Schizochytrium limacinum (ALG) to replace fish meal (FM), squid meal (SQM) and fish oil (FO). Diets were formulated to contain 45% protein (dry weight) and 10% lipid. Three diets were derived from this formulation, using combinations of SBM, SPC, and ALG to replace 20% (FM80), 40% (FM60), or 80% (FM20) of the marine-origin protein sources; additionally, incorporation of the lipid-dense ALG resulted in complete FO replacement in the FM60 and FM20 diets. A feeding experiment was carried out in a seawater recirculating system with 12, 90-L tanks initially stocked with 6 fish each (individual weight = 45.9 ± 7.1 g) and maintained at 25 °C. Diets were assigned to tanks in triplicate, fish were fed to apparent satiation twice daily for 12 weeks, and growth rate, body composition, nutrient retention, survival, hepatosomatic index and intestinal integrity were subsequently evaluated. With the exception of retained lipid, the FM100, FM80, and FM60 diets all yielded equivalent (P > 0.05) growth and feed utilization. In comparison, weight gain, specific growth rate, feed intake, retained nitrogen and retained lipid were significantly reduced in fish fed the FM20 feed, whereas FCR was significantly elevated. Amino acid analysis of the diets indicated that methionine was limiting in the FM20 feed. Hepatosomatic index did not vary among treatments, but other aspects of body composition were affected. Carcass lipid and ash significantly decreased with marine ingredient inclusion; carcass protein also varied, though less appreciably and without a clear pattern. Fillet fatty acid profile reflected dietary composition. The FM100 diet yielded the highest fillet EPA content, whereas DHA content, DHA:EPA and n − 3:n − 6 ratios, and total long-chain polyunsaturated fatty acids increased with dietary inclusion of ALG. Histological analysis revealed progressive morphological changes to the distal intestine with higher levels of FM replacement, suggesting enteritis among fish fed the FM20 feed. It is concluded that a blend of SBM, SPC, and ALG can replace at least 40% of marine protein sources, and ALG can be used as the main lipid source in diets for E. lanceolatus without significantly affecting fish performance or condition. Statement of relevance The results of this work contribute to decrease the dependence on protein and lipids from reduction fisheries traditionally used in commercial feeds for carnivorous fish, potentially improving the sustainability of aquaculture production of marine fish. [ABSTRACT FROM AUTHOR]

Fish meal (FM) was partially replaced by soy protein concentrate (SPC), squid meal and a defatted algal meal from Haematococcus pluvialis in low-fish oil (FO) diets for longfin yellowtail ( Seriola rivoliana ). A 50% protein/15% lipid, FM-based diet (FM100) was used as a Control, and four experimental diets were formulated replacing FM with SPC, squid and H. pluvialis meals at levels of 25% (FM75), 40% (FM60), 60% (FM40) and 80% (FM20). Dietary lipid was supplied by blends of FO, a docosahexaenoic acid (DHA)-rich algal meal from Schizochytrium limacinum , and canola oil. With exception of FM100, all diets were supplemented with methionine and lysine. Taurine was supplemented in all diets to achieve a dietary concentration of 1.5%. Diets were fed twice daily for nine weeks to triplicate groups of 20 fish (initial mean weight 2.5 ± 0.1 g) kept in 1000-L circular tanks in a flow-through seawater system. The effects of diet treatment on fish growth, feed utilization, body proximate composition, nutrient retention, fillet fatty composition, and intestinal integrity were evaluated. Growth rate and feed conversion ratio of longfin yellowtail fed the SPC-algal diets were largely comparable to that of fish fed the FM100 diet. Small, but significant differences in nitrogen retention were observed, with fish fed the FM100 diet outperforming those fed the FM 40 and FM 20 diets. Lipid retention was highest in fish fed the FM20 diet and the lowest in the FM75 diet treatment. Fillet fatty acid profile reflected dietary composition and was altered by the level of FM replacement. Lower n − 3 and long-chain polyunsaturated fatty acid (LC-PUFA) levels, higher n − 6 fatty acid levels, and reduced n − 3:n − 6 ratios were associated with increasing FM replacement. Incorporation of the S. limacinum meal partially attenuated dietary and tissue loss of DHA, however, EPA levels declined with increasing FM sparing. No major histological differences or signs of enteritis were observed in any dietary treatments. Results indicate that up to 80% of FM can be replaced by SPC and algal meal, even in low-FO diets, without significantly affecting performance or intestinal integrity of longfin yellowtail. Statement of relevance It is shown that FM can be substantially reduced using blends of SPC, squid and algal meals in diets for longfin yellowtail with no significant effect on fish growth and intestinal tissue integrity. The results contribute to the knowledge to improve the sustainability of aquafeeds by using blends of terrestrial and aquatic plant ingredients. [ABSTRACT FROM AUTHOR]

The present study assessed the use of saturated fatty acid-rich lipids to replace fish oil in grow-out feeds in conjunction with a fish oil-rich finishing diet to determine if this strategy could produce hybrid striped bass with equal production performance, and equivalent fillet long-chain polyunsaturated fatty acid (LC-PUFA) levels, and reduced fillet persistent organic pollutant (POP) concentrations. Final weight (597.8±11.1g, mean±SE, p=0.29), percent weight gain (2743.1±45.1%, p=0.11), feed conversion ratio (1.4±0.02, p=0.28), dress-out (23.5±0.3%, p=0.46), hepatosomatic index (0.9±0.02, p=0.54), or liposomatic index (1.5±0.04, p=0.62) was not adversely affected by any of the feeding regimens. However, fillet composition was altered, with fillets of fish consuming less fish oil having lower LC-PUFA (31.45±0.75 to 16.94±0.78g/100g FAME, p<0.0001) and POP levels (53.93±9.21 to 15.97±9.49ng/g dry weight, p<0.0001). Finishing yielded a modest increase in fillet LC-PUFA and POP, but POP accumulated more readily than LC-PUFA with increased fish oil consumption during finishing. Replacing fish oil in aquafeeds produces fish with reduced LC-PUFA and POP in the fillet. Feeding fish oil results in more rapid accumulation of POP than LC-PUFA. Overall, fish consuming the lowest amount of fish oil in the diet yielded fillets with the highest ratio of LC-PUFA to POP, despite lower LC-PUFA content. [ABSTRACT FROM AUTHOR]