A n-3 PUFA depletion applied to rainbow trout fry (Oncorhynchus mykiss) does not modulate its subsequent lipid bioconversion capacity

AbstractNutritional strategies are currently developed to produce farmed fish rich inn-3 long-chain PUFA (LC-PUFA) whilst replacing fish oil by plant-derived oils in aquafeeds. The optimisation of such strategies requires a thorough understanding of fish lipid metabolism and its nutritional modulation. The present study evaluated the fatty acid bioconversion capacity of rainbow trout (Oncorhynchus mykiss) fry previously depleted inn-3 PUFA through a 60-d pre-experimental feeding period with a sunflower oil-based diet (SO) followed by a 36-d experimental period during which fish were fed either a linseed oil-based diet (LO) (this treatment being called SO/LO) or a fish oil-based diet (FO) (this treatment being called SO/FO). These treatments were compared with fish continuously fed on SO, LO or FO for 96 d. At the end of the 36-d experimental period, SO/LO and SO/FO fish recovered >80 % of then-3 LC-PUFA reported for LO and FO fish, respectively. Fish fed on LO showed high apparentin vivoelongation and desaturation activities along then-3 biosynthesis pathway. However, at the end of the experimental period, no impact of the fishn-3 PUFA depletion was observed on apparentin vivoelongation and desaturation activities of SO/LO fish as compared with LO fish. In contrast, the fishn-3 PUFA depletion negatively modulated then-6 PUFA bioconversion capacity of fish in terms of reduced apparentin vivoelongation and desaturation activities. The effects were similar after 10 or 36 d of the experimental period, indicating the absence of short-term effects.