Development of less-polluting diets for practical fish culture. I. Development of low protein-high energy diets for practical carp culture with special reference to reduction of total nitrogen excretion.

Abstract

Two feeding experiments were conducted for both practical and experimental scales to develop low-protein high-energy diets (less-polluting diets) for practical carp culture in order to reduce the total nitrogen excretion from the fish. Results of both the experiments have demonstrated that diets containing 32-37% crude protein (CP) with digestible energy (DE) above 340kcal/100g diet enriched with carbohydrate or lipid were found to be better than a commercial cazp diet containing CP above 40% in growth and feed efficiency. This fact indicated that CP content in practical carp feeds can be reduced from 40% to around 30% without reduction of growth rate and feed efficiency, if a high quality protein is used as protein source and DE content is increased by carbohydrate or lipid to about 340kcal/100g diet. The total nitrogen excretion from carp was also found to be reduced by 30-48% of the present value by feeding these low protein-high energy diets.