Evaluating the effects of 17 α-Methyltestosterone and nano chitosan on masculinization rate and growth performance in Nile tilapia (Oreochromis niloticus) using the immersion method

The study aimed to evaluate the effectiveness of combining 17 α-Methyltestosterone (MT) with nano chitosan on the survival rate, masculinization rate, and growth performance of Nile tilapia (Oreochromis niloticus) using the immersion method. A completely randomized design was conducted, with five treatment groups receiving varying concentrations of MT and nano chitosan: chitosan + 1 mg MT/L (1 MC), chitosan + 1.5 mg MT/L (1.5 MC), chitosan + 2 mg MT/L (2 MC), chitosan + 2.5 mg MT/L (2.5 MC), and chitosan + 3 mg MT/L (3 MC). A control group was also included, with each treatment replicated three times. Seven-day-old fry were exposed to the MT solution for 2 h before being transferred to nurseries in hapas within earthen ponds at a stocking density of 1,500 fish/m² for a 60-day rearing period. After 2 h of hormone treatment and the 60-day rearing period, the 2.5 MC treatment exhibited the highest survival rate. Male ratios in the MT treatments ranged from 76.67% to 83.33%, significantly higher than in the control group (55.56%) (P < 0.05). Specifically, the male ratios in the 2.5 MC and 3 MC treatments were 82.2% and 83.3%, respectively, which were higher than those in the other MT treatments, however,these differences were not statistically significant (P > 0.05). While the mean weight and length of fish in the MT treatments were greater than those in the control group, these differences were also not statistically significant (P > 0.05). The study further revealed a positive correlation between the average weight of the fish and the hormone concentration. Based on these findings, a dose of 2.5 mg 17 α-MT/L in combination with nano chitosan is recommended for achieving optimal mono-sex male tilapia production.