Influence of Grow-Out Feed Fatty Acid Composition on Finishing Success in Nile Tilapia

The fatty acid (FA) composition of cultured finfish can be tailored by transitioning fish reared on alternative lipid-based, low long-chain polyunsaturated FA (LC-PUFA) content grow-out feeds to high LC-PUFA finishing feeds based on fish oil (FO) before harvest. To determine whether the FA composition of the grow-out feed influences finishing success in Nile tilapia Oreochromis niloticus, coconut (CO), grapeseed (GO), linseed (LO), and poultry (PO) oils were evaluated in grow-out feeds with respect to production performance and responsiveness to finishing. The production performance of Nile tilapia was unaffected by application of the various feeding regimes, indicating that this species can effectively utilize CO, GO, LO, PO, and FO in aquafeeds. Implementation of the alternative lipid sources was associated with altered fillet FA composition. Although the differences were not significant in all cases, the levels of FO-associated FAs (e.g., 20:5[n-3] and 22:6[n-3]) were elevated among finished groups relative to their unfinished counterparts. However, the effect of finishing on fillet LC-PUFA content was relatively minor given the considerable retention of LC-PUFAs observed in unfinished groups. The patterns of fillet FA profile change in Nile tilapia appear to support a hypothesis of selective FA metabolism in this species. Our results suggest that attempts to enhance the FA composition of Nile tilapia fillets via finishing may be best served by providing a grow-out feed high in saturated and monounsaturated FAs and low in medium-chain polyunsaturated FAs