Abstract
A feeding trial was conducted in order to determine the optimum ratio of energy to protein in the diet (DE kcal/protein %) of carp by feeding them various diets containing different amounts of protein (22-41%), carbohydrate (5-50%), and lipid (5 and 15%). The growth rate and feed conversion of the fish fed diets containing 23% protein were quite low, regardless of the DE content in the diet. These values were improved as the dietary protein levels were increased, reaching a maximum in the 31-32% protein diets with DE contents of 310-360 kcal/100g, and were not affected by the enrichment of dietary DE content from 310 to 460 kcal in each protein level by using carbohydrate or lipid. The values for both PER and NPU were significantly lower in the fish fed diets with DE content of less than 310 kcal. The rate of energy retention in the fish body was 32-49%, regardless of the DE levels in the diets or the growth of the fish. The digestibility of energy was found to be proportional to the cellulose content in the diet and decreased with and increase in dietary cellulose levels.
Judging from the results of the feeding experiment and the analytical data, the optimum content of dietary protein for the maximum growth of carp is estimated to be around 31%. The experimental value of the optimum DE/protein for the optimum growth was 97-116 when based on the measured digestible energy.
