N-3 Canola oil effectively replaces fish oil as a new safe dietary source of DHA in feed for juvenile Atlantic salmon.

Bente Ruyter,Gerd M Berge,Tone-Kari Østbye,Monica Sanden,Aleksei Krasnov,Peter D Nichols,Nini H Sissener,Esmail Lutfi,Cedric J Simon,Marta Bou

doi:10.1017/s0007114519002356

Abstract

Limited availability of fish oils (FO), rich in n-3 long-chain (≥C20) PUFA, is a major constraint for further growth of the aquaculture industry. Long-chain n-3 rich oils from crops GM with algal genes are promising new sources for the industry. This project studied the use of a newly developed n-3 canola oil (DHA-CA) in diets of Atlantic salmon fingerlings in freshwater. The DHA-CA oil has high proportions of the n-3 fatty acids (FA) 18 : 3n-3 and DHA and lower proportions of n-6 FA than conventional plant oils. Levels of phytosterols, vitamin E and minerals in the DHA-CA were within the natural variation of commercial canola oils. Pesticides, mycotoxins, polyaromatic hydrocarbons and heavy metals were below lowest qualifiable concentration. Two feeding trials were conducted to evaluate effects of two dietary levels of DHA-CA compared with two dietary levels of FO at two water temperatures. Fish increased their weight approximately 20-fold at 16°C and 12-fold at 12°C during the experimental periods, with equal growth in salmon fed the FO diets compared with DHA-CA diets. Salmon fed DHA-CA diets had approximately the same EPA+DHA content in whole body as salmon fed FO diets. Gene expression, lipid composition and oxidative stress-related enzyme activities showed only minor differences between the dietary groups, and the effects were mostly a result of dietary oil level, rather than the oil source. The results demonstrated that DHA-CA is a safe and effective replacement for FO in diets of Atlantic salmon during the sensitive fingerling life-stage.

Highlights

Diets for farmed Atlantic salmon, Salmo salar, have changed considerably during the last decades
The n-3-rich modified canola oil (DHA-CA) had a higher level of total vitamin E forms compared with the control canola oil (Ctr-CA), which was primarily due to an increased level of γ-tocopherol, with values of 325 mg/kg in the DHA-CA compared with 282 mg/kg in the Ctr-CA
The undesirables normally detected in canola oils used in commercial fish feeds were not detected or were below limit of quantification in the two canola oils (DHA-CA and Ctr-CA) used in the current feeding trials

Summary

Introduction

Diets for farmed Atlantic salmon, Salmo salar, have changed considerably during the last decades. The high inclusion levels of vegetable and/or animal oils rich in n-6 FA in salmon diets result in an associated increase in the n-6:n-3 ratio in fish organs and tissues, including fish fillets[11]. This is an important issue that might affect fish and human consumer health and influence consumer perspectives towards farmed fish. The overall study was undertaken to determine if the new DHA-CA oil containing enhanced levels of n-3 LC-PUFA and a lower level of n-6 LC-PUFA than conventional canola oils would influence growth, performance, health and n-3 LC-PUFA, content in different organs and tissues in Atlantic salmon fingerling

Methods

Results

Discussion

Conclusion