# The Effects of Hormone Diets with Different 17β-Estradiol Levels on Growth and Feminization in Long-Whiskered Catfish (Mystus gulio) Larvae Using Conventional and Microencapsulated Feed

## TL;DR

This study shows that feeding long-whiskered catfish larvae with microencapsulated 17β-estradiol leads to faster growth and nearly all-female populations, improving aquaculture sustainability.

## Contribution

The study introduces microencapsulated 17β-estradiol feeding as an effective and eco-friendly method for producing monosex female catfish.

## Key findings

- Microencapsulated feed with 60 mg/kg 17β-estradiol achieved the highest growth rate and feed efficiency.
- Feminization success reached 99.73% with microencapsulated hormone diets.
- Ovarian development was confirmed through hormonal, histological, and gene expression analyses.

## Abstract

The long-whiskered catfish (Mystus gulio) is a valuable aquaculture species because female fish grow faster and provide higher economic returns than males. This species is commonly cultured alone or together with other aquatic animals such as seabass and shrimp, where it helps maintain cleaner pond conditions by consuming leftover feed on the bottom. It can adapt well to different salinity levels, from freshwater to seawater, making it an excellent candidate for sustainable aquaculture. In this study, young catfish were fed diets containing different levels of the natural female hormone 17 β-estradiol, provided either in regular feed or in specially designed microencapsulated feed that allows for slow hormone release. The results showed that microencapsulated diets with the highest hormone level produced faster growth, better feed use, and an almost completely female population. Microscopic and genetic analyses confirmed the successful development of ovaries in these fish. These findings demonstrate an effective and environmentally responsible technique for producing all-female catfish, improving productivity, reproductive potential, and long-term sustainability in aquaculture operations.

Feminization is an important biotechnological approach in aquaculture for species in which females exhibit superior growth and higher market value. The long-whiskered catfish (Mystus gulio), a euryhaline species cultivated in both monoculture and co-culture systems, contributes to sustainable aquaculture by grazing on uneaten feed and maintaining pond cleanliness. This study evaluated the effects of dietary 17β-estradiol (E2) at 0, 10, 30, and 60 mg/kg, incorporated into conventional and microencapsulated feeds, on the feminization and early growth of M. gulio larvae. Treatments were administered during the weaning stage for 14 and 21 days under controlled rearing conditions. Results showed that larvae fed microencapsulated feed containing 60 mg/kg E2 achieved the highest specific growth rate (26.91 ± 1.92%/day), feed efficiency (164.76 ± 33.23%), and feminization success (99.73 ± 0.04%). Hormonal assays confirmed elevated estradiol and reduced testosterone levels, consistent with ovarian development observed in histological sections. Gene expression analysis further supported these findings through the significant upregulation of cyp19a, erb1, and erb2 mRNA levels. Overall, this study demonstrates that microencapsulated hormone feeding is an effective and environmentally responsible strategy for achieving monosex female populations in M. gulio, enhancing productivity, reproductive performance, and sustainability in aquaculture systems.