Response of juvenile freshwater prawn, Macrobrachium rosenbergii, to different levels of a cod liver oil/corn oil mixture in a semi-purified diet

Abstract

Two separate experiments were conducted to determine the level of a dietary cod liver oil/corn oil (2:1, w/w) mixture needed for maximum weight gain of juvenile freshwater prawns, Macrobrachium rosenbergii. Seven isoenergetic and isonitrogenous purified diets with levels ranging from 0 to 12% in 2% increments were evaluated in each experiment that began with newly metamorphosed postlarvae. Diets used in the first experiment had protein and estimated digestible energy levels that were slightly higher than those used in the second experiment. After termination of both experiments, juveniles receiving the diet without the oil addition had significantly lower weight gains. Significant differences in weight gain responses to different levels of lipid were identified. Some relationships differed between experiments. Neither survival nor the time interval between molts was influenced by the level of the oil mixture. A dietary lipid level ranging from 2 to 10% under a wide range of dietary lipid:carbohydrate ratios appears to be satisfactory, indicating that juvenile freshwater prawns do not require a specific level of dietary lipid. Rather, the optimal amount of dietary lipid depends upon the amount and quality of dietary protein, the level of available dietary energy, and satisfaction of specific fatty-acid requirements.