Investigation into gonadal feminization of farmed sterlet Acipenser ruthenus upon oral genistein administration focused on reducing the dose, shortening the administration period, and optimizing the initiation

Abstract In the preceding study, the induction of feminization in genetically male sterlet was achieved through the administration of a genistein (GS) dosage of 1000 µg/g feed for 180 days, commencing at 8 weeks posthatch (WPH). The present study, composed of two experiments, was conducted to investigate the effects of 8- or 16-week administration of 500 or 1000 µg GS/g feed, and 16-week administration of 1000 µg GS/g feed initiated at 8, 16, or 24 WPH. Individuals with developed oocytes in the testes were observed at both doses in the 16-week administration group, and genetic males with complete ovaries observed in the group administered 1000 µg GS/g feed. The highest number of individuals with developed oocytes in the testes was identified in the groups initiated at 8 WPH, and individuals with complete ovaries were identified in the group fed a GS feed initiated at 8 WPH. In the context of a feminization induction focused on oocyte development in the testes, a dosage of 500 µg GS/g feed, administered initiating at 8 WPH, has demonstrated a promising treatment within the experimental range. However, a 16-week feeding period with a GS-containing feed was insufficient to induce complete ovarian development in all individuals.