Dietary Open Water Chlorella vulgaris Meal Modulates Growth, Antioxidant Defenses and Metabolic Responses of Clarias magur

Abstract

The present study evaluated the open raceway-cultured Chlorella vulgaris meal (CVM) as an ingredient in the diet of Clarias magur fingerlings. Five isonitrogenous (35% crude protein), isolipidic (6%), and isoenergetic (350 kcal digestible energy/100 g) experimental diets by gradually  replacing fish meal (FM) with C. vulgaris meal (CVM) on protein equivalent basis, viz., C (Control with 20% FM, 0%
CVM), T₂₅ (15% FM, 7.30% CVM), T₅₀ (10% FM, 14.60% CVM), T₇₅ (5% FM, 21.80% CVM), and T₁₀₀ (0% FM, 29.13% CVM) were formulated. A total of 150 acclimatised fingerlings were randomly distributed among five treatments (C, T₂₅, T₅₀, T₇₅, and T₁₀₀) in triplicate using 15 experimental tanks at a stocking density of 10 fish/200 L tank and fed for 60 days. The 50% fishmeal replacement group showed the highest growth, with 11–12% greater (p < 0.05) final body weight and weight gain than the control, while the 75% replacement group maintained comparable growth. Activities of amylase, ALT, LDH, and SOD were unaffected, whereas those of chymotrypsin, ALP, ACP, MDH, and catalase increased in CVM-fed groups (50%, 75% & 100%). Overall, inclusion of 21.8% open raceway-cultured C. vulgaris
effectively replaced 75% of fishmeal without compromising growth or physiological health, supporting its use as a sustainable aquafeed ingredient.