Exploring the use of microalgae in salmon feeds: effects on growth, health and flesh quality

Offentlig prosjektsammendrag

The primary aim of this project is to investigate the performance of salmon diets containing microalga-meals in comparison with a commercial-like diet containing a large proportion of plant proteins. Briefly, we will compare four diets containing 7,5% algal meals (extruded Nannochloropsis, broken/unbroken Phaeodactylum or defatted Desmodesmus) to a commercial-like diet containing a conventional mixture of fishmeal and plant meals (15% fishmeal, ~70% plant ingredients). The trial will be set up with 15 cages, triplicate cages per diet. The fish will have an average weight of 2,4 kg at the start (August 2019) and the trial will be run until the fish reach an average weight of 5 kg (expected December 2019). Feeding will be done manually and to satiation twice a day and, using the lift-up system at GIFAS, the uneaten pellets will be collected and counted for an adequate estimate of the feeding efficiency. Growth rates of the fish will be followed by individually weighing the fish at the start and bulk weighing at the mid and end of the trial. Dead fish, if any, will be collected on a daily basis for an assessment of survival. In conjunction with bulk weighing, a variety of tissue samples will be collected on the start and end time points. Samples will be used for assessments of growth, flesh quality, antioxidant status and intestinal health. The future of the salmon aquaculture industry is threatened by the shortage of adequate feed ingredients. Fish meal, which was traditionally used to fulfill the salmon's protein requirements, depends on declining fisheries. Plant meals, which have been explored in recent years, are produced unsustainably and, furthermore, cause gut inflammation in salmon. In this project, we propose microalgae as a replacement for fish meal. Such an ingredient is expected to be more agreeable to salmon health and welfare, and it is also possible to produce in large quantities with minimal environmental impact.