Reproductive effects of dietary soy phytoestrogens, genistein and equol on farmed female beluga, Huso huso

In this study, 54 five-year-old farmed female beluga at stage II of sexual maturation were treated with 0 (control), 0.2, 0.4, 0.8 and 1.6 g of dietary soy equol (EQ) and genistein (GE) per each kilogram (kg) of diet during a year. Blood samples were collected and ovarian biopsy was performed quarterly. Results showed that 64.4% of the Huso huso sexually matured at EQ 0.4 g/kg and reached stage IV of sexual maturation. Oocytes diameters increased significantly at all concentrations of EQ and 0.2, 0.4 and 0.8 concentrations of GE and reached a maximum (3 ± 0.2 mm) at 0.4 g/kg EQ concentration at the end of experiment (P<0.05). Blood plasma testosterone (T) level was 0.3 ± 0.06 ng/ml at the beginning and reached a maximum (21.04 ± 1.91 ng/ml) at EQ 0.4 g/kg at the end of the experiment (P<0.05). 17β-estradiol (E2) levels increased significantly at some concentrations of GE and EQ at the end as compared to the beginning, reaching a maximum (12.6 ± 1.04 ng/ml) at EQ 0.4 g/kg at the end of the experiment (P<0.05). 17α-hydroxy progesterone (17α-OHP) levels showed no significant difference (P>0.05). In conclusion, EQ at a 0.4 g/kg concentration showed more powerful positive reproductive effects than other concentrations of EQ and GE in farmed female H. huso. Comparatively, EQ showed more estrogenic effects on ovary development in comparison to GE concentrations. Its use is therefore suggested as an additive to diets to induce ovary development in Huso huso.