Pit-tagging of rainbow trout to validate method for feed efficiency

Foods of Norway, a center for research-based innovation (SFI), has a special focus on improved breeding strategies to increase the feed efficiency and robustness of fish and farm animals. The aim is to support genetic adaptation and identify new selection criteria for both fish and farm animals, with the major goal to develop a method for large-scale evaluation of feed efficiency in aquaculture production. The aim of this experiment is to develop a cost-effective experimental feed that can be used to assess individual feed efficiency in rainbow trout, without requiring individual feed intake recording. As the feed amount to ~50% of the production cost per kg produced fish in the grow-out phase, improvement in feed efficiency by 1% will increase the present annual value in Norway alone by EUR ~23 million and reduce the environmental footprint per unit produced. Nevertheless, there is a need for a method which allows for a more efficiently selection for feed efficiency in aquaculture breeding programs. During this trial, we will test three different experimental diets with different ratios of 15N/14N and 13C/12C, to assess individual feed efficiency in rainbow trout. All diets will be formulated according to the requirements of rainbow trout in the freshwater stage. To be able to follow individual weight changes, it is necessary to insert a small pit-tag (microchip) in each fish at the start of the experiment. This procedure also help reduce the number of fish used in the experiment. A total of 315 pit-tagged fish (~100 g start weight) will be divided into 9 tanks. During the experimental trial (35 days), several terminal samplings will be conducted to register individual growth and to sample different organs to measure individual feed efficiency. Dissection and sampling of organs will only be done after the fish have been euthanized, followed by a blow to the head. The data from this experiment will provide vital knowledge that can be used to select more efficiently for feed efficiency in aquaculture breeding programs. Furthermore, there is no available in vitro models that can mimic entire body systems, thus it is not possible to use in vitro methods.