Fish oil replacement in feeds for juvenile Florida Pompano: Composition of alternative lipid influences degree of tissue fatty acid profile distortion

Abstract

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 C18 polyunsaturated fatty acids (C18 PUFAs) are equally suitable in this context. Accordingly, we assessed the production performance and tissue composition of juvenile Florida Pompano (43.4±0.2g) fed diets containing menhaden fish oil (FISH) or 25:75 blends of fish oil and standard soybean oil (C18 PUFA SOY), MUFA-enriched soybean oil (MUFA SOY), SFA-enriched soybean oil (SFA SOY), palm oil (PALM), or poultry fat (POULTRY). After 8weeks, 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 C18 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 relevanceAs 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.