Towards green aquaculture: Withania coagulans as a natural feed additive for sustainable and healthier production of Ctenopharyngodon Idella

Introduction: Incorporating natural immunostimulants into aquafeed provides is an eco-friendly approach to ensure sustainable and healthier aquaculture production. Methods: Two feeding trials (initial weight: 4.21 ± 0.51 g for 42 days and 4.10 ± 0.63 g for 84 days) were conducted to evaluate the effects of dietary supplementation of Withania coagulans on growth performance and health status in juvenile grass carp (Ctenopharyngodon idella). Fish were divided into groups and fed either on a control diet (0% W. coagulans) or diets supplemented with increasing levels of W. coagulans (0.5%, 01%, 1.5%, 02%, and 2.5%) three times a day until apparent satiation. Statistical differences (p < .05) among experimental groups were assessed by one-way ANOVA followed by Tukey’s LSD test. Quadratic regression was done to determine the optimal concentration of the feed additive. Results: Results obtained from both trials showed that the optimal dietary supplementation of W. coagulans significantly improved (p < 0.05) growth and metabolic efficiency in C. idella. The optimal inclusion levels were determined to be 2.08% for a short term (42 days) feeding and 1.3% for a long term (84 days) feeding by using the quadratic regression analysis. The supplementation beyond optimal level in the long term feeding trial showed negative effects on growth and health parameters, revealing that intake of the test nutrient at higher concentrations for prolonged periods may restrict feed intake and growth in grass carp and induce oxidative stress. Conclusions: The optimal dietary supplementation of W. coagulans significantly improved growth and health in juvenile grass carp during both feeding trials. However, excessive dietary inclusion for prolonged periods compromised these benefits, possibly due to the adverse effects of antinutritional factors and secondary metabolites. Further research is recommended to determine the optimal inclusion of W. coagulans for large-size grass carp and other high-value species.