EFFECTS OF FEEDING 17-ALPHA-METHYLTESTOSTERONE, 11-KETOTESTOSTERONE, 17-BETA-ESTRADIOL, AND 3,5,3'-TRIIODOTHYRONINE TO CHANNEL CATFISH, ICTALURUS-PUNCTATUS

Channel catfish, Ictalurus punctatus, were fed 17-alpha-methyltestosterone (MT) or 11-ketotestosterone (KT) at dietary levels of 5 and 32 mg kg-1, and beta-estradiol (E2) or 3,5,3'-triiodothyronine (T3) at dietary levels of 5 and 50 mg kg-1 under laboratory conditions. Among all treatments, only the lowest dose of KT produced a significant increase in weight gain over the control. This treatment also caused a reduction in body fat and an increase in body protein. The higher levels of KT and all levels of the other compounds had a neutral to negative effect on weight, protein and fat gains. Fish fed the androgens had broad heads, exophthalmia and dark skin. These fish had enlarged, precociously mature testes while ovaries were not affected. The fish fed E2 or T3 had dark skin, and those fed T3 had broad heads, exophthalmia, and thickening at the base of the fins. The fish fed E2 had degenerated oocytes but testes were not affected. Liver and kidneys of fish from all treatments were examined histologically. In the fish fed E2, the nuclei of many of the hepatocytes were near the sinusoids rather than centrally located as in the control. Vacuolation of epithelial cells of renal tubules in the trunk kidney was found in all treated fish but not in the control.