Dietary Wolffia globosa extract enhances innate immunity, serum biochemical responses, antioxidant defense, and expression of related gene in Labeo rohita under winter thermal stress.

INTRODUCTION

Temperature is a key environmental factor regulating physiological, biochemical, and immunological processes in ectothermic fish such as Labeo rohita. Exposure to low-temperature conditions during winter disrupts metabolism, suppresses immunity, and induces oxidative stress, thereby compromising fish health and productivity.

METHODS

Labeo rohita fingerlings (initial weight: 8.35 ± 0.50 g) were randomly distributed into four dietary treatments with three replicates each and fed isonitrogenous (25% crude protein) and isocaloric (16.5 MJ kg-1 gross energy) diets supplemented with graded levels of Wolffia extract (WGE; 0, 0.5, 1.5, and 3.0 g kg-1) for 75 days. The experiment was conducted in outdoor cemented tanks during the winter season (December-March) under natural low-temperature conditions (18-22 °C).

RESULTS

Dietary WGE significantly enhanced (P< 0.05) non-specific immune responses, with anti-protease activity increasing by 8.22-12.32%, myeloperoxidase by ~200-300%, respiratory burst by 76.92%, and lysozyme by up to 146.94% compared to the control. Carcass composition improved significantly, with crude protein reaching 18.01% and lipid 4.63%. Serum glucose decreased (15.78-49.26%), while total protein and albumin increased. Liver function markers, including SGOT, SGPT, ALP, and CK-MB, declined significantly, indicating improved hepatic integrity and reduced physiological stress. Antioxidant status improved, with elevated SOD and CAT activities and reduced MDA levels by up to 43.97% (liver) and 46.69% (serum). Gene expression analysis revealed downregulation of stress-related genes (hsp70: 0.042-fold; hsp90: 0.147-fold) and upregulation of immune-related genes (c3: 5.51-fold; tnf-α: 3.37-fold; ifn-γ: 7.73-fold).

CONCLUSION

This study evaluated the protective effects of Wolffia globosa extract on innate immunity, antioxidant defense, and stress- and immune-related gene expression in Labeo rohita. Dietary WGE effectively mitigated cold-induced stress by improving immune function, antioxidant capacity, and metabolic performance. Among the tested levels, 1.5 g kg-1 WGE provided the most balanced physiological benefits, while higher inclusion levels induced stronger immune and antioxidant responses. These findings highlight the potential of Wolffia globosa as a sustainable functional feed additive for enhancing fish resilience under low-temperature conditions.