The main purpose of this study was to consider the impact of Vitex agnus-castus hydroalcoholic extract, containing phytoestrogenic compounds on growth indices, sex ratio and histology of gonads of female Zebrafish. Fish larvae (4-day-old after hatching) were nourished with investigational diets (0 (control group T0), 5 g (T1), 10 g (T2) and 15 g (T3) kg−1 food) from first active feeding for 90 days. The results showed that Condition Factor (CF), Food Conversion Rate (FCR), Body Weight Gain (BWG), and Specific Growth Rate (SGR) were affected meaningfully by hydroalcoholic extract of Vitex agnus-castus (p < 0.05). These factors were significantly higher in compare to T3 treatment (p < 0.05). With increasing concentration of the extract in the diet, the ratio of female to male increased Treatment of T3 resulted in 87.23% feminization. Overall, this study suggests the use of T3 treatment achieves the best reproduction performance and a higher percentage of females in zebrafish as a model for aquaculture species. According to the results, the lowest levels of glucose and cholesterol were observed in T3 treatment and showed a significant changes with the control and treatments (p < 0.05).

Zebra fish is an important species in genetics and considering the proximity of its genome to the human genome, investigating the expression of some of the growth and appetite genes during its larvae development is essential. Genes coding growth and appetite (GH and ghrelin) hormones are involved in the synthesis and release of growth hormone, which can be considered to be economic genes in pisciculture. Given the importance of these genes during the early larvae development stages, this study was performed to assess their activity. Samples were collected at 4, 7, 10, 15, 30 and 45 post-hatching days. Samples were immediately placed in liquid nitrogen (-196 degree centigrade) and then stored in a freezer at-80 degree centigrade until RNA extraction (using RNX-Plus kit). To analyze normal expression of target genes, reference gene β-actin was used by 2-∆∆Ct method. The expression of genes associated with the growth and appetite was significantly different at various stages of the development of zebra fish, as the gene expression of GH on day 4 and ghrelin gene on day 10 after hatching were significantly higher compared with other samples (P<0.05). Overall, the expression of GH and ghrelin genes at the early stages of growth is higher than other fish developmental stages due to their great importance in the survival of larvae at these stages of life.