GENERAL AND COMPARATIVE ENDOCRINOLOGY @,409-424 (1980) The Effect of Feeding Methyltestosterone on the Growth and Body Composition of Common Carp (Cyprinus carpio L.) KHALID P. LONE AND A.J. MATTY Department of Biological Sciences, The University of Aston in Birmingham, Birmingham 84 7ET. United Kingdom Accepted September 12, 1979 Groups of juvenile common carp were fed diets supplemented with 17o- methyltestosterone (MT) at doses of 1.0,2.5,5.0, and 10 mglkg diet for 90 days and the effect on growth, food conversion, and body composition was observed. MT, when given at lower doses, significantly increased the growth and food conversion. After 90 days of drug feeding the net weight gain over the controls was 40.41, 39.00, 18.25, and -6.08 for l.O-, 2.5-, 5.0-, and 10ppm groups, respectively. Significant increase in length was also observed. Termina- tion of drug feeding did not arrest the impetus of growth, although there was a slight decrease in the specific growth rate (SGR) during the period of 60 days without the drug. The effect of MT feeding on hepato-, reno-, crania-, and viscerosomatic indices was variable. After 90 days of drug feeding a significant increase was observed in total protein and RNA and in the protein/DNA ratio in liver, kidney, brain, and muscle. While cholesterol de- creased in liver, kidney, and brain, it increased in muscle. An increase in total lipid and decrease in moisture content of the muscle was also noted. The results are discussed in relation to possible commercial implications. There has been considerable work on the nutritional requirements of fish for maximising growth responses (Cowey, 1975; Cowey and Sargent, 1972,1977, 1979; Halver, 1972). The role of hormones in fish growth has gained tremendous importance, particularly due to the increase in produc- tion costs (food and capital expenditure) in aquaculture. Economy in this connection can be achieved by use of the hormones as food additives for increased growth rates and food conversion efftciencies, as has long been done in animal husbandry (for re- cent reviews see Bird, 1976; Velle, 1977; Scott, 1978; Trenkle and Burroughs, 1978). Donaldson et al. (1979) have summarized the studies on the hormonal control of growth in fish. Following the example of the livestock industry, estrogens and their derivatives were first investigated for their effects on growth in fish. The results of these studies were confusing and contradictory (Ashby, 1975; Ghittino, 1970; Bulkley, 1972; Cowey et at, 1973; Matty and Cheema, 1978). During the last decade, anabolic-an- drogenic steroids have been used in growth studies. Hirose and Hibiya (1968a,b) re- ported positive effects of intramuscular in- jections of 4-chlorotestosterone on the growth of goldfish and rainbow trout, whereas Stanozolol (17a-methyl-17p-hy- droxy-5a-androstane - (3,2-C)-pyrazole), when given to immature goldfish and channel cattish, did not induce any signifi- cant growth (Bulkley and Swihart, 1973). 17cy-Methyltestosterone, a synthetic deriva- tive of testosterone, which is active orally, has been studied in detail in different salmonids (McBride and Fagerlund, 1973, 1976; Fagerlund and McBride, 1975, 1977; Simpson, 1976; Yamazaki, 1976; Higgs et al., 1977; Saunders et al., 1977; Yu et al., 1979), and this steroid appears to hold considerable promise in aquaculture. Recently Matty and Cheema (1978) have reported the anabolic actions of dimeth- azine and norethandrolone (synthetic steroids) in Salmo gairdneri. Growth is largely protein accretion and RNA levels 409 0016~6480/80/040409-16$01.00/O Copyright 0 1980 by Academic Press, Inc. All rights of reproduction in any form reserved.