Abstract
A feeding trial was conducted to define the optimal mixtures of either sunflower oil (SFO) or linseed oil (LO) with fish oil (FO), in fish meal (FM) based diets for gilthead seabream ( Sparus aurata ) fingerling, without significant effect on fish performance, fatty acid composition and liver structure. The trial lasted nine weeks with 420 fish (~4.0 g) testing seven isonitrogenous (~48% CP) and isolipidic (~18% L) diets contained three incremental inclusions of either SFO or LO (40, 48, 56 g kg -1 ) and the only-fish oil control (CTRL) diet. Results showed that the combination of 32 g fish oil plus 48 g of either SFO or LO kg -1 diet as the lipid source had performed the best among all. Fatty acid (FA) composition of muscle lipids evidenced that specific fatty acids were selectively retained or utilized. Diet induced- changes in hepatic morphology with vegetable oil inclusion level were further described. Linolenic acid ( α -LNA, n -3) had led to less pronounced steatosis symptoms than linoleic acid (LOA, n -6) in liver cells. This study provides sound support for the use of preferably sunflower oil then linseed oil as a complementary lipid resource (48 g kg diet -1 ) with marine fish oil in gilthead seabream fingerling diets. Therefore, represents novel data on the potential of using sunflower oil (SFO) as a possible dietary partial substitute of fish oil for the species.
Highlights
The importance of lipids, in aquaculture feeds, as a major source of energy and essential fatty acids neccessary for optimal fish growth is well documented
Total n-3 LcPUFA content gradually decreased and n-6 polyunsaturated fatty acids (PUFA) gradually increased within the experimental diets with each elevation of either linseed oil (LO) or sunflower oil (SFO) incorporation level
Estimated amount of n-3 LcPUFA in the VO-added diets was 5.5–11.1% (DM of total Fatty acid (FA)), and ecosapentenoic acid (EPA) plus docosahexaenoic acid (DHA) level (3.5–8.4% respectively) was considered satisfactory to cover the theoretical requirements of this species juvenile
Summary
The importance of lipids, in aquaculture feeds, as a major source of energy and essential fatty acids neccessary for optimal fish growth is well documented. There are a range of alternatives that have already been examined and each has some potential, few are ideal and most have little if any LcPUFA content (Glencross, 2009). Plant/vegetable oils (VO) are promising and sustainable source as FO-substitutes in aquafeeds, because of their wide availability and competitive price their use is limited by deficiencies in ω-3 LcPUFA essential for carnivorous species. Extensive research effort on the use of vegetable oils as dietary lipid source in compounded aquafeeds for several marine fish species are already ongoing and are reviewed by Turchini et al (2009, 2010) and Glencross (2009)
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