The effect of replacement of vegetable oils with fish oil on gonadal development and sex steroid hormones in female rainbow trout (Oncorhynchus mykiss)

To study the effect of dietary animal and plant lipids on gonadal differents and sex steroid hormones levels of blood in rainbow trout (Oncorhynchus mykiss), the four diets was formulated based on 15% fat. The control uses 100% oil, fish oil was treated in the first, second and third respectively 25% and 75% fish oil, soybean oil, canola and cotton were used. After six weeks of feeding fish with average weight 200±2.5 (g), ovarian tissue and sex steroid hormones levels of blood (Testosterone, Progesterone, 17β-Estradiol) were evaluated. Development of ovarian tissue as well as the hormones testosterone and 17β- Estradiol in the first treatment was significantly greater than other treatments (P<0.05), while progesterone hormone between different treatments and control treatments did not show significant difference. According to the presented study, the best oils in diets for rainbow trout ovarian tissue development and increased levels of see steroid hormones, soybean oil is suggested.