FEEDING FREQUENCY AND RATION SIZE ALTER THE METABOLISM OF WHITE TRUNK MUSCLE IN COD (GADUS-MORHUA)

Fish (Gadus mcrhua) were fed for 158 days a maximum ration or a ration 50 % that of the maximum. The feeding schedule was once every day, every 2nd, 4th or 8th day. Growth rate and muscle wet weight decreased with the extended intervals of feeding or by feeding the 50 % ration. Protein and RNA content per g wet weight of muscle decreased after feeding the maximum ration every 8th day or half the ration at all different time intervals. The fraction of sarcoplasmic origin was affected more than that of myofibrillar origin. Hybridization of mRNA with a probe specific for myosin heavy chain showed a decrease in signals after feeding the 50 % ration suggesting a diminished capacity for the synthesis of that protein. Muscle glycogen content increased by supplying the maximum ration at extended time intervals and decreased with the 50 % ration. Acid proteinase activity increased after feeding the maximum ration every 8th day and more so with the 50 % ration. Giving the maximum rations at prolonged time intervals was less detrimental to muscle performance than daily feeding of the 50 % ration.