Protein Requirements of Carp and Rainbow Trout

Abstract

The protein requirement to give the maximum protein retention was determined with carp, Cyprinus carpio, and rainbow trout, Salmo gairdneri, by the following two methods, 1) the nitrogen balance determinations at the different nitrogen intake (carp) and 2) the determinations of the carcass-nitrogen increments when these fish were fed on the diets containing the proteins with high biological values. The protein requirement determined with these two methods was 12-13g/kg body weight/day and there was no appreciable difference between carp and rainbow trout. The value was almost equal to that of the swine of 10kg body weight and lower than that of broiler chickens. The dietary protein levels required for the maximum protein retention decreased with increase in the feeding rate, namely, when the feeding rate increased from 2.5% to 3.5% of the body weight, the protein level for the maximum retention decreased from around 50% to 35%. These results indicate that the optimum protein content in the diets of carp and rainbow trout is from 35% to 50% under the conditions of various feeding rates.