Abstract
Oral administration of an estrogen, sodium diethylstilbestrol (DES-Na) was found to promote the growth in Japanese eel elvers when DES-Na was mixed with the basal feed at the level of 0.5-1.0 ppm; the higher the dose, the faster the growth. However, it retarded the growth when applied at the levels above 2.5 ppm. The elvers of 0.3g grew to 22-28g within 104 days at the temperature of 23.0-25.5°C when they fed on the feed having 1.0 ppm DES-Na; the final body weight was 2.7 times of that of control group. Including the control group, the specific daily growth rate in body weight ranged 0.033-0.044. The feed efficiency was 12-19% in terms of wet weight. Since the maintenance ration during the experimental period did not changed in spite of different mean body weight, DES-Na is thought to save the maintenance cost under the optimal application.
