Effects of Spirulina platensis Supplementation on Growth, Hematological Indices, Biochemical Responses, Digestive Enzymes, Carcass Composition, Antioxidant Defense and Pigmentation in Blue Gourami (Trichogaster trichopterus)

Abstract

Market value in the ornamental fish industry is primarily determined by pigmentation quality, growth performance and overall physiological health. Blue Gourami (Trichogaster trichopterus) is a popular ornamental species, yet information on natural dietary additives to enhance its commercial traits remains limited. Spirulina platensis, a nutrient-rich microalga containing proteins, vitamins, minerals and carotenoids, represents a promising natural alternative to synthetic pigments and chemotherapeutics. This study evaluated the effects of graded dietary Spirulina supplementation on growth, hematological and serum biochemical parameters, digestive enzyme activity, immune response, antioxidant status and pigmentation in Blue Gourami. A 90-day feeding trial was conducted using 480 male fingerlings (1.09–1.16 g), distributed into six dietary treatments containing 0% (T0), 2% (T1), 4% (T2), 6% (T3), 8% (T4) and 10% (T5) Spirulina platensis. Fish were fed twice daily to satiation. Growth indices, blood parameters, serum biochemistry, digestive enzymes, immune markers, colour attributes and tissue carotenoid content were analyzed. Results demonstrated significant dose-dependent improvements with increasing Spirulina levels. Fish fed 10% Spirulina (T5) exhibited the highest growth performance and feed efficiency (FCR 1.47), improved hematological and serum biochemical profiles, enhanced digestive enzyme activities and improve immune responses. Pigmentation intensity and carotenoid deposition in skin and caudal fins were also maximized in T5. Overall, dietary supplementation with 10% Spirulina platensis significantly enhanced growth, health, immunity and coloration in Blue Gourami, supporting its application as an effective natural feed additive for improving ornamental fish quality. Further studies should explore long-term reproductive performance, disease resistance under pathogen challenge and costbenefit analysis of Spirulina inclusion at commercial scale.