Omega-3 long-chain polyunsaturated fatty acids and aquaculture in perspective

Abstract

Abbreviations: ARA, arachidonic acid (20:4n-6); CVD, cardiovascular disease; DHA, docosahexaenoic acid (22:6n-3); DPA, docosapentaenoic acid (22:5n-3); EFA, essential fatty acid; Elovl, fatty acid elongase; EPA, eicosapentaenoic acid (20:5n-3); Fads, fatty acyl desaturase; FM, fishmeal; FO, fish oil; LC-PUFA, long-chain polyunsaturated fatty acids (≥ C20 ≥ 3 double bonds); LOA, linoleic acid (18:2n-6); LNA, linolenic acid (18:3n-3); PUFA, polyunsaturated fatty acid; TAG, triacylglycerol; VO, vegetable oil. ABSTRACTIn the 40 years since the essentiality of polyunsaturated fatty acids (PUFA) in fish was first established by determining quantitative requirements for 18:3n-3 and 18:2n-6 in rainbow trout, essential fatty acid (EFA) research has gone through distinct phases. For 20 years the focus was primarily on determining qualitative and quantitative EFA requirements of fish species. Nutritional and biochemical studies showed major differences between fish species based on whether C 18 PUFA or long-chain (LC)-PUFA were required to satisfy requirements. In contrast, in the last 20 years, research emphasis shifted to determining "optimal" levels of EFA to support growth of fish fed diets with increased lipid content and where growth expectations were much higher. This required greater knowledge of the roles and functions of EFA in metabolism and physiology, and how these impacted on fish health and disease. Requirement studies were more focused on early life stages, in particular larval marine fish, defining not only levels, but also balances between different EFA. Finally, a major driver in the last 10-15 years has been the unavoidable replacement of fish oil and fishmeal in feeds and the impacts that this can have on n-3 LC-PUFA contents of diets and farmed fish, and the human consumer. Thus, dietary n-3 in fish feeds can be defined by three levels.Firstly, the minimum level required to satisfy EFA requirements and thus prevent nutritional pathologies. This level is relatively small and easy to supply even with today's current high demand for fish oil. The second level is that required to sustain maximum growth and optimum health in fish being fed modern high-energy diets. The balance between different PUFA and LC-PUFA is important and defining them is more challenging, and so ideal levels and balances are still not well understood, particularly in relation to fish health. The third level is currently driving much research; how can we supply sufficient n-3 LC-PUFA to maintain the nutritional quality of farmed fish at the same level as 20 years ago, and similar or better than in wild fish? This level far exceeds the biological requirements of the fish itself and to satisfy it we require entirely new sources of n-3 LC-PUFA. We cannot rely on the finite and limited marine resources that we can sustainably harvest or 3 efficiently recycle. We need to produce n-3 LC-PUFA de novo and all possible options should be considered.Keywords: Fish oil; essential fatty acids; nutrition; health; metabolism; sustainability 4 Highl...

Eicosapentaenoic Acid, Arachidonic Acid and Eicosanoid Metabolism in Juvenile Barramundi Lates calcarifer

“…However, many studies have investigated interactions between DHA, EPA and ARA or n-3 to n-6 ratios in fish and the general consensus is that size and species differences exist and that an appropriate balance between these essential fatty acids is critical Tocher, 2015). Consistent with the present study, several studies in larval and juvenile fish such as the Atlantic salmon Salmo salar (Thomassen et al, 2012), cobia Rachycentron canadum (Trushenski et al, 2012), gilthead sea bream Sparus aurata (Atalah et al, 2011a), Senegalese sole Solea senegalensis (Villalta et al, 2008), striped jack Pseudocaranx dentex (Watanabe et al, 1989) and turbot Scophthalmus maximus (Bell et al, 1995) all concluded that EPA does not stimulate an improved growth response.…”

“…In many vertebrate and fish species, EPA and ARA are required for important metabolic and physiological functions, and the optimal as well as dietary requirements are well understood (Bell and Sargent, 2003;Das, 2006;Glencross, 2009;Izquierdo, 1996;Tocher, 2010;Tocher, 2015). In addition, there is great potential for dietary ARA to affect growth, stress response, immune response and survival, particularly at early life stages (Atalah et al, 2011a;Atalah et al, 2011b;Bell and Sargent, 2003;Castell et al, 1994;Montero et al, 2015b;Norambuena et al, 2016;Yuan et al, 2015).…”

“…In humans, the incidence of diseases involving inflammatory processes can be related to the production these eicosanoids, for example prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) that are derived from high cellular concentrations of ARA (Tocher, 2015;Wall et al, 2010). The cyclooxygenase (COX; prostaglandin G/H synthase) and lipoxygenase (LOX; arachidonate 5-lipoxygenase) enzymes interact and compete for the EPA and ARA substrates and as such the eicosanoids produced are determined by their availability (Calder, 2012;Tocher, 2003).…”

Evaluation of Dicentrarchus labrax Meats and the Vegetable Quality of Beta vulgaris var. cicla Farmed in Freshwater and Saltwater Aquaponic Systems

“…These are mostly contained in seafood and play a crucial importance to human health. In fact n-3 PUFAs are considered to have beneficial effects on inflammatory and cardiovascular diseases, neural development and even a protective effect against some kinds of cancers [33]. More specifically, eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) are the most important n-3 PUFAs responsible for fish meat quality and human healthiness [33].…”

Crustacean amphipods from marsh ponds: a nutritious feed resource with potential application in Integrated Multi-Trophic Aquaculture.

“…Fish accounted for 16.7% of the global population's intake of animal protein and 6.5% of 69 all protein consumed in 2010 (FAO, 2014;Tocher, 2015 (Tocher, 2015). Fishmeal and fish 74 oil is at base of carnivorous species aquaculture due to their n-3 LC-PUFA, but that depends on 75 limited and overexploited fisheries.…”