The effect of dietary carbohydrates on muscle metabolism, connective tissue composition and fillet quality in cod (Gadus morhua L).

Post mortem softening of fish muscle and occurrence of gaping are major problems for the fish industry. Muscular connective tissue provides mechanical integrity, rigidity, and elasticity to skeletal muscles. Extracellular matrix (ECM) represents an import ant part of the connective tissue, and changes in ECM composition could have major impacts on fish fillet quality. Previous studies have shown that carnivorous fish, such as cod, have poor capacity to handle high glucose loads, and may be considered diabe tics. From medical studies of diabetes and prediabetes, there is evidence that these conditions affect muscle metabolism, ECM composition and activity of lysosomal enzymes involved in ECM degradation. Thus, we hypothesise that dietary carbohydrates affect cod fillet quality by altering metabolism and ultimately changing the ECM composition. This will be tested by performing feeding trials where effects of different levels and sources of carbohydrates in feed on fillet quality (i.e. gaping and texture), mu scle metabolism and ECM composition will be investigated. This project will enhance our basic knowledge on the relationship between dietary carbohydrates and fillet quality of cod, and provide information regarding possible molecular mechanisms, such as E CM composition and muscle metabolism, of importance for cod fillet quality. Moreover, this project will provide information regarding the health aspect of feeding carbohydrates to a carnivorous fish, as it will discover if metabolic disturbances seen in h umans are also apparent in cod. This study will provide a basis for optimising feed composition in order to optimise product quality of cod fillets and enhance fish health. If carbohydrate content can be increased and fish meal content reduced accordingl y, this will benefit the aquaculture industry by reducing feed costs. In addition, reduced demand for fish meal can significantly benefit the environment and reduce the stress placed on limited marine supplies.