Investigating the potential of nannochloropsis meal in diets for rainbow trout

Marine microalgae are spotlighted as potentially valuable ingredients for fish nutrition. Their high protein content, balanced amino acid profile and most importantly omega-3 fatty acids make them a fundamental component of the marine lifecycle and therefore an interesting candidate for the aquafeed industry, especially for salmonids. Under the roof of the EU-Project iFishIENCi, Aller Aqua Research (AAR) investigated the potential of a microalgae meal (Nannochloropis gaditana) in test diets for rainbow trout. In the initial trial, main interest was given to feed palatability, nutrient digestibility and fatty acid profile of the ingredient, produced at the Norwegian Research Centre (NORCE), located in Bergen, Norway. The test feed was processed at ttz Bremerhaven in Germany. Under optimal environmental conditions, feeding was conducted twice a day until apparent satiation for a period of 8 weeks. Daily feed intake was comparable between the test diet and a fishmeal-based control diet, indicating a good palatability of feed pellets. The apparent protein digestibility of the ingredient was 92.4 %, which is within the range of suitable raw materials for rainbow trout nutrition, typically ranging from 90-95%. Considering the omega-3 fatty acids, the Nanno meal has been found to be rich in EPA but reveals a lack of DHA.At the end of the trial, an effective pigmentation of fillet was determined. Currently, the Carotenoid spectrum of the Nanno meal is analysed by in cooperation with NORCE to get a better understanding of the Nanno meal-mediated pigmentation process. Subsequent trials will focus on performance and health stimulating effects of this microalgae.