Substitution of limited marine feed ingredients alters the level and total composition of minerals in salmon feeds. Substitution of marine feed ingredients with plant ingredients will also lower the bioavailability of already supplemented minerals due to the presence of plant fibers and phytate. The lower mineral bioavailability in novel aquafeeds will therefore affect essential elements required for fish health and robustness, as well as increasing the environmental load by increased loss via the faeces. High supplementation of several minerals to fish feeds today, merely based on precautions, may also interact with each other both on intestinal uptake and in biological function. The chemical form (e.g. inorganic or organic forms) of supplemented minerals has been suggested to alter the bioavailability, but the routes of uptake and tissue distribution for chemical forms has not been demonstrated in fish. Establishing mineral requirements in the Atlantic salmon relates to the chemical forms of the minerals in the feed ingredients and complete diets, as well as interacting factors that may elevate the requirements. In the project,we will develop a chemical speciation method of selected minerals to predict mineral digestibility depending on mineral chemical species. We will apply rapid in situ and in vitro methods to assess intestinal mineral uptake with combined factors that can affect bioavailability. Based on the digestibility and availability studies, we want to re-establish safe minimum requirement levels of zinc, manganese and selenium to support growth performance and robustness in farmed Atlantic salmon fed future environmentally friendly feeds.
The main objectives in this project are:
1. To examine if chemical mineral speciation analysis can be used as a predictive measure of apparent mineral digestibility in Atlantic salmon.
2. To study mineral bioavailability through examining intestinal routes, rates of uptake and distribution of different chemical forms of minerals in vitro.
3. To estimate practical and conditional requirements of Zn, Mn and Se in future feeds for Atlantic salmon, mainly in the seawater phase, based on established and novel biomarkers.
4. Based on dietary mineral feed level, digestibility, feed intakes and mineral retentions in feeding trials we will calculate the environmental load of microminerals in salmon farming under variable farming conditions,and including use of triploid salmon.