Study on the effect of phytoestrogen genistein on sex hormones of rainbow trout (Oncorhynchus mykiss) larvae in sex differentiation stage

Phytoestrogens are plant-based and anti-nutrient substances that usually have estrogenic activities. These substances affect gonadal evolution and sexual differentiation in some aquatic species. Phytoestrogens may have a similar effect to estrogen or, conversely, have the ability to block the effect of estrogens. One of the plants used in the diet of fish, especially Rainbow trout, is soy and its derivatives. One of the most important phytoestrogenic compounds in soy is Genistein. In the present study, genistein was administered in three doses of 40, 400 and 800 mg/kg of feed to larvae during the sex differentiation period. 17 beta-Estradiol treatment and Methyl Testosterone treatment were also considered for comparison. The larvae of one treatment did not receive any hormones as a control treatment. The duration of hormonal feeding to larvae was 60 days from the beginning of active feeding and at the end of the hormonal feeding period, the levels of 17 beta-Estradiol, Testosterone and 17 OH-Progesterone, Vitellogenin level and free phosphate level in different treatments were evaluated and compared. The results showed that at the end of the hormonal feeding period, phytoestrogen Genistein did not have an acute and significant effect on the levels of sex steroids and Rainbow Trout larvae Vitellogenin and partially reduced sex steroids, especially 17 beta-Estradiol and 17 OH-progesterone. The highest level of 17 beta-Eestradiol was measured in treatment E and the treatments containing Genistein had lower levels of this hormone (P≤0.05). Also, the level of Vitellogenin was somewhat lower in the treatment of Genistein but the change in the amount Feed Genistein did not show a significant difference in this regard (P> 0.05).