Nutritional effects of ethyl ester oils in Atlantic salmon and Rainbow trout

Background

The Norwegian pelagic sector is an important industry in the production and processing of marine oils, including the production of high-quality omega-3 concentrates for human consumption.

In the process of concentrating the content of the omega-3 fatty acids EPA and DHA, the by-product ethyl ester oil (EE) is formed. In Norway, around 10,000 tonnes of EE oils are produced annually.

A potential area of use for EE oil is as an ingredient in salmon feed. However, there is limited knowledge about how suitable EE oil is as an ingredient in feed for salmon and rainbow trout.

In general, marine EE oils will be relatively rich in saturated fat, and contain both cholesterol, EPA and DHA. EE oils will thus be able to contribute important fatty acids in the feed for salmonids.

Goal

 In SalmoE2, we aim to test whether ethyl ester (EE) oil can be used as a safe source of nutritionally beneficial fatty acids in the feed for salmon and trout.

What we do

Nofima is the project manager and will be in charge of all activities within the project.

First, different levels of EE oil will be tested in the feed for salmon pre-smolts (dose-response) in freshwater to increase knowledge about safe feed levels. Fast-growing salmon parr (5-10 g) will be fed respectively a control feed (with a composition corresponding to a commercial feed) as well as 5 experimental feeds with increasing levels of EE oil (5, 10, 20, 25 and 50% of the total oil fraction ) for 5-6 weeks (triplicate tanks, 100 fish per tank).

Results from this experiment will form the basis for choosing EE oil doses in the post-smolt study.

Then, the nutritional effects of EE oil in the feed for salmon and trout will be compared. Both species will be fed the same experimental diets.

The experiment will start with salmon and trout of approx. 200-400g which will be fed a control feed without EE oil and 3 experimental feeds with 3 levels of EE oil (in triplicate tanks and 30-40 fish per tanks) until they triple the weight. Oxidative stability of EE oil and feed is analyzed by analyzing volatile oxidation products (storage stability).

The feeds for both trials are produced by Nofima. Adjustments will be made based on the composition of the EE oil supplied by Pelagia AS.