Restriction of lipid deposition in the liver of cod by use of bioactive substances in salmon oil and vegetable feed ingredients.

Use of high-energy feeds has been of major importance for the development of cost effective farming of fast growing salmonids. High energy diets contain high levels of lipids, and such diets cause development of a large fatty liver in cod. More than 80% o f total body lipids in cod are in fact found in the liver. Obviously a large part of the dietary energy is retained as liver lipid stores, which again means that this lipid deposition in the liver account for a large part of the feed costs in cod producti on. Since the liver is a by-product of less value than cod filet, and further that marine lipid is a limited resource, it is of major importance for the cod farming industry to develop strategies to decrease the excess of lipid deposition in the liver. T he basic aim of the proposed project is therefore to find other dietary means which will allow for more of the ingested lipid to be used for energy in stead of being deposited in the liver. This also leaves more of the protein for deposition in muscle gro wth. Salmon oil is a by-product from the salmon farming industry, and the possibility to use this resource in diets for cod, in stead of marine oils from wild stocks, will be studied. The use of lipid for energy may be achieved by stimulating fatty acid ( FA) oxidation for instance by dietary inclusion of specific FAs like EPA from salmon oil or bioactive compounds from plant seeds. New knowledge on the physiological mechanisms that affect development of fatty liver in cod is essential for the development of an efficient and sustainable cod production. The project therefore seeks to answer 1) what mechanisms are involved in regulation of lipid deposition in liver of cod? 2) how can we control unwanted fat deposition by dietary means?