Genistein can have both estrogenic

Genistein can have both estrogenic and antiestrogenic effects, either of which, in turn, can have stimulatory or suppressive actions on growth and reproduction in fish (Green and Kelly, 2009). In the present study, fish fed genistein supplemented diet showed no significant change in growth (P>0.05) compared to the control fish. Similarly, growth performance of rainbow trout Oncorhynchus mykiss was not affected by dietary treatments with genistein-enriched diets (Bennetau-Pelissero et al., 2001). Exposure to genistein showed no significant reduction in survival and growth in fathead minnows, Pimephales promelas. However, chronic exposure to high concentration of this phytoestrogen may result in reproductive impairment in fish (Ingham et al., 2004). Although isoflavone content within diets, soybean meal, and the beans themselves is highly variable, the increased replacement of fish meal with soybean products has increased the amount of total isoflavones in fish diets. Soy protein concentrate and diets with high proportions of soybean meal replacing fish meal contain a high amount of genistein. Under this context, further studies are required to determine the ideal treatment regime with this phytochemical during aquaculture.