Influence of dietary Schizochytrium limacinum oil on growth performance, reproductive development, and testicular histo-architecture of genetically selected growth trait (SGT) Clarias magur male

Sustainable seed production of genetically selected growth-trait Clarias magur is a promising candidate for aquaculture diversification due to its superior growth rate and adaptability. However, it is a significant challenge to raise the quality of male brooders in captivity for commercial-scale seed production. The present study aimed to evaluate the effects of marine algal oil, Schizochytrium limacinum (SMAO), on growth performance, reproductive development, and testicular histoarchitecture of genetically selected growth trait (SGT) Clarias magur males through supplementation in broodstock diets at four different levels (SMAO 2%, SMAO 3%, SMAO 4%, and SMAO 5%), with fish oil (FO 3%) serving as the control, in a completely randomised design using 15 circular FRP tanks of 1000 L capacity, each holding 15 fish (ten males and five females) with a mean standard length of 24.3±0.86 cm and a mean weight of 96.04±4.14 g fish fed with 5% of body weight for 90 days. The SMAO 4% diet resulted in the highest weight gain (16.50±2.1 g) with the lowest feed conversion ratio (2.23±0.65). The highest gonad weight (0.55±0.12 g), gonadosomatic index (0.52), and abundant spermatozoa in the testis histology were observed in the SMAO 5% diet. The sperm density varied across SMAO treatments and the FO group, and higher spermatocrit value (94.39%) and sperm density (14.40×109 cells mL–1). In conclusion, SMAO supplementation at 4% enhances growth and captive maturation in male SGT magur, while 5% SMAO promotes higher sperm cell abundance in testes, supporting its use in sustainable broodstock development.