Abstract
Omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFA) are essential components of the diet of all vertebrates. The major dietary source of n-3 LC-PUFA for humans has been fish and seafood but, paradoxically, farmed fish are also reliant on marine fisheries for fish meal and fish oil (FO), traditionally major ingredients of aquafeeds. Currently, the only sustainable alternatives to FO are vegetable oils, which are rich in C18 PUFA, but devoid of the eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) abundant in FO. Two new n-3 LC-PUFA sources obtained from genetically modified (GM) Camelina sativa containing either EPA alone (ECO) or EPA and DHA (DCO) were compared to FO and wild-type camelina oil (WCO) in juvenile sea bream. Neither ECO nor DCO had any detrimental effects on fish performance, although final weight of ECO-fed fish (117 g) was slightly lower than that of FO- and DCO-fed fish (130 and 127 g, respectively). Inclusion of the GM-derived oils enhanced the n-3 LC-PUFA content in fish tissues compared to WCO, although limited biosynthesis was observed indicating accumulation of dietary fatty acids. The expression of genes involved in several lipid metabolic processes, as well as fish health and immune response, in both liver and anterior intestine were altered in fish fed the GM-derived oils. This showed a similar pattern to that observed in WCO-fed fish reflecting the hybrid fatty acid profile of the new oils. Overall the data indicated that the GM-derived oils could be suitable alternatives to dietary FO in sea bream.
Highlights
Fish is considered as the main source of the beneficial omega-3 (n-3) long-chain polyunsaturated fatty acids (LCPUFA) eicosapentaenoic and docosahexaenoic acids, EPA (20:5n-3) and DHA (22:6n-3), respectively
There were no significant differences in weight gain or specific growth rate (SGR) other than it being slightly lower in fish fed EPA-Camelina oil (ECO) compared to fish fed fish oil (FO) (Table 3)
Previous trials completely replacing FO by vegetable oils (VO) in feeds for gilthead sea bream resulted in reduced growth probably related to a reduced intake of essential long-chain polyunsaturated fatty acids (LC-PUFA), which are not found in VO [31,32,33]
Summary
Fish is considered as the main source of the beneficial omega-3 (n-3) long-chain polyunsaturated fatty acids (LCPUFA) eicosapentaenoic and docosahexaenoic acids, EPA (20:5n-3) and DHA (22:6n-3), respectively. In a world where the global population is expected to grow to reach 9.6 billion people by 2050 [7], more than 1.7 million metric tonnes of EPA + DHA would be necessary to cover annual human requirements. This quantity is not met by the actual total global supply of n-3 LC-PUFA and there is a large gap between supply and demand [8, 9]. Recent studies have successfully demonstrated the feasibility of using both the high-EPA and EPA + DHA oils as substitutes for FO in feeds for post-smolt Atlantic salmon (Salmo salar) without compromising fish growth or health [13,14,15]
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