Abstract
Two trials were performed using extruded diets as on-growing feeds for weaned Atlantic bluefin tuna (Thunnus thynnus; ABT) to establish adequate dietary levels of both lipid and omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs), and impacts on lipid metabolism via liver gene expression. In trial A, ABT were fed with either a commercial feed (Magokoro®; MGK) as a reference diet or two experimental feeds differing in lipid levels (15 or 20%) using krill oil (KO) as the single lipid source in order to estimate suitable lipid content. Fish fed MGK displayed the highest growth, followed by 15KO, and therefore a dietary lipid content of 15% was considered preferable to 20% at this stage. In trial B, fish were fed MGK, 15KO, or a feed containing 15% lipid with a blend of KO and rapeseed oil (RO) (1:1, v/v; 15KORO). Fish fed 15KO and 15KORO showed no difference in weight gain, specific growth rate, and fork length. Increasing dietary lipid level or including vegetable oil, RO, in the feeds did not increase liver lipid content. Liver fatty acid compositions largely reflected dietary profiles confirming very limited endogenous LC-PUFA biosynthesis. Liver of ABT fed 15KO and 20KO displayed the highest contents of docosahexaenoic acid (DHA). The hepatic expression of genes encoding enzymes and transcription factors involved in lipid and fatty acid metabolism, as well as genes encoding antioxidant enzymes, showed that many of these genes were regulated by dietary lipid and LC-PUFA content. Results suggested that ABT juveniles can be on-grown on inert dry feeds that support good fish growth and the accumulation of DHA.
Highlights
The vast majority of Atlantic bluefin tuna (ABT) production from aquaculture is derived from fattening operations based in the Mediterranean Sea with the three main producer countries being Spain, Croatia, and Malta (Benetti et al 2016; van Beijnen 2017)
B, a Magokoro® (MGK) reference, b 15% lipid diet based on krill oil (15KO), and c 15% lipid diet based on krill oil and rapeseed oil 1:1; v/v (15KORO)
(MGK), b 15% lipid diet based on krill oil (15KO), and c 15% lipid diet based on krill oil and rapeseed oil 1:1; v/v (15KORO)
Summary
The vast majority of Atlantic bluefin tuna (ABT) production from aquaculture is derived from fattening operations based in the Mediterranean Sea with the three main producer countries being Spain, Croatia, and Malta (Benetti et al 2016; van Beijnen 2017). Captured wild ABT (mostly adult broodstock fish and some juveniles) are towed in sea pens to fattening farms where they are fed mainly on baitfish of variable quality (Benetti et al 2016; van Beijnen 2017). The development of formulated sustainable feed is essential for the farming of tuna species, whether in fattening or, closed life-cycle culture (van Beijnen 2017). Formulated diets for rearing juvenile PBT, including nutrient sources and requirements for crude protein, lipids, carbohydrates, and vitamin C, were established (Biswas 2010; Biswas et al 2016). The partial or full replacement of fish oil (FO) sources with soybean oil (SO) for this species was investigated (Biswas et al 2011)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
