Royal Jelly as a Natural Endocrine Modulator of Serum Estradiol Levels in Juvenile Sterlets (Acipenser ruthenus)

The present study investigates the role of royal jelly as a natural endocrine modulator of serum estradiol levels in juvenile sterlets (Acipenser ruthenus), a species of major interest for sustainable aquaculture. The experiment was conducted over a period of 85 days under controlled recirculating system conditions, using four dietary treatments (n = 30 fish per group): a control group and three groups supplemented with 1%, 3%, and 5% royal jelly. Serum estradiol concentrations were determined by high-performance liquid chromatography (HPLC), while biometric assessment included the determination of total length (L), standard length (Sl), maximum body height (H), body circumference (C), and body mass (BM). Royal jelly supplementation significantly increased serum estradiol levels in a dose-dependent manner (p < 0.05), with the highest values recorded in the 5% group compared to the control. The proportion of individuals with non-detectable estradiol levels decreased progressively with increasing supplementation level. Biometric analysis revealed moderate effects on growth parameters, with no statistically significant differences among groups for most traits (p > 0.05), except for maximum body height, which showed a significant overall effect (ANOVA, p = 0.0089). Principal Component Analysis (PCA) highlighted the relative independence between endocrine variability and growth dynamics. Overall, the findings support the potential of royal jelly as a natural endocrine modulator of serum estradiol, representing a promising and environmentally friendly alternative to synthetic hormonal substances used in aquaculture. This approach may contribute to the development of innovative nutritional strategies for endocrine control and the optimization of biological performance in sturgeons, in accordance with the principles of sustainable aquaculture.