Phytase in Atlantic salmon

Loss of phosphorous to the environment is a major challenge in fish farming. The most important vegetable protein feed ingredients contain large amounts of phytin that binds phosphorous making it unaccessible to the fish. This requires increased additions of phosphorous to fish diets which causes major losses to the environment through fish feces. The aim of this trial is to induce phytin degradation by use of dietary phytase. This has the potential to significantly reduce phosphorous loss through feces and reduce feed cost production. The society benifits are major as fish farming today is a major source for phosphorous released into nature. The scientific value is in the mechanisms on how phytase works in salmon compared to other species. Phytase does not have any effect on fish health or welfare (no suffering of the fish) and the only extected effect is increased phosphorous availability. The trial will last over 3 months plus a 2 week adaptation period. The Atlantic salmon will be 400g, distributed into 5 triplicate dietary groups with increased enzyme inclusion. Each tank will contain 30 fish with a biomass of 12 kg/m3 which will give little social interactions. In vitro trial for salmon can not replace live trials for phytase tests. The handling of the fish is at a minimum. The only handling will be feces stripping and blood sampling under anasthesia at the end of trial. Remaining fish will be anaesthetized and killed before other sampling is done (10 fish/tank).