Chitosan nanoconjugation of GnRH analogue augments reproductive performance in Clarias magur (Hamilton, 1822)

Abstract

A breeding trial was conducted to investigate the impact of a chitosan nanoconjugated formulation of Salmon gonadotropin-releasing hormone analogue (ChN-sGnRH-a) on the induced breeding performance of female Clarias magur (magur). A total of 72 magur breeders were divided into six treatment groups: Cn, the Negative Control (injected with bare chitosan nanoparticles); Cp, the Positive Control (injected with Gonopro-FH®, a commercially available inducing hormone, at a dose of 1 mL/kg body weight of fish); T1, injected with ChN-sGnRH-a at a dose of 1 mL/kg; T2, T1 + 10 mg/kg domperidone; T3, injected with ChN-sGnRH-a at a dose of 0.5 mL/kg; T4, T3 + 10 mg/kg domperidone. Blood was collected at 0 (before injection), 6, 12 and 18 h post-injection to determine the serum steroid profile. In the Cp treatment group, the serum steroid levels of testosterone, estradiol, and 17α, 20β-dihydroxy progesterone in the fish, displayed a sharp increase, peaking at the 6-h post-injection, followed by a significant decrease. However, the fish in the T2 and T4 treatment groups exhibited serum steroid peaks at the 12-h post-injection and maintained those levels up to the 18-h post-injection. The reproductive performance, as measured by spawning fecundity, fertilization rate, and hatching rate, was significantly higher in the T2 treatment group (p < 0.05). No significant differences (p > 0.05) were observed between the Cp and T4 treatment groups. Compared to the Cn treatment group, the mRNA expression levels of pituitary follicle stimulating hormone subunit beta and luteinizing hormone subunit beta, as well as ovarian 17β-hydroxysteroid dehydrogenase type 3, were significantly higher in the T2 treatment group, followed by Cp and T4 treatment groups. Fish in the T2 treatment group displayed fewer mature oocytes and numerous post-ovulatory follicles in their ovaries. Additionally, the ovarian histology of fish in the T4 treatment group closely resembled that of the Cp treatment group. The results indicate that the chitosan nanoconjugated formulation of Salmon GnRH analogue might contribute to maintaining elevated levels of gonadotropic and steroid concentrations, resulting in improved reproductive output in female magur breeders. It is also revealed that the induced breeding of magur cannot be achieved without using dopamine inhibitors in GnRH analogue injection. Using chitosan nanoparticles as a nano-delivery system could reduce the Salmon GnRH analogue dose without compromising the reproductive performance of female magur breeders.