Growth, reproduction and sex ratios in Oreochromis andersonii (Castelnau, 1861) fed with varying levels of 17α-methyl testosterone

Abstract

Three different doses (40, 60 and 90 mgMT/kg feed) of 17α-methyl testosterone (MT) were administered to Oreochromis andersonii. Growth, reproduction and sex ratios were evaluated. The fish raised on 60 mgMT/kg feed had the highest final mean weight and this was signifcantly different (P<0.05) from other hormone doses. Additionally, the 60 mgMT/kg fed fish had the lowest fecundity and reproductive effort. Histological examination of the gonads did not show any differences between the control and MT fed fish. The gross margin ratio (GMR) of the control group was the highest (P<0.05). The proportion of males in MT treated groups deviated signifcantly from the control group although the percentage of males obtained from the 40 mgMT/kg feed (93.4%) and 60 mgMT/kg feed (94.4%) fish was insignificant (P>0.05). Furthermore, the highest dose used produced a signifcantly lower (P<0.05) male proportion (79.3%) than the other treatments. The anabolic effect of androgen MT diminished over time. © 2012 Kef AS, et al.