Effects of dietary liquid Spirulina platensis on growth performance and oxidative status of common carp

Abstract

The development of circular and sustainable feed ingredients is a major priority in modern aquaculture. Liquid microalgal cultures represent a promising alternative to dried biomass, allowing the direct use of fresh algae together with the growth medium, reducing processing costs and preserving bioactive compounds. This study evaluated the effects of dietary inclusion of a liquid culture of Spirulina platensis on growth performance, flesh quality, hematological profile, and oxidative status of common carp (Cyprinus carpio). Juvenile carp were fed experimental diets supplemented with 5%, 10%, or 15% liquid Spirulina platensis culture, compared with a control diet. All supplemented diets significantly improved growth performance, including final body weight, weight gain, feed conversion ratio, specific growth rate, and relative growth rate. Polynomial trend analysis indicated an initially near-linear growth response followed by a curvature at the highest inclusion level, with optimal performance at 10% inclusion. Somatic indices (condition factor, hepatosomatic and viscerosomatic indices) were not significantly affected, indicating no adverse physiological effects. Dietary supplementation improved flesh composition by increasing protein content and reducing lipid levels. Hematological parameters exhibited dose-dependent responses, while antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase) were enhanced across tissues, accompanied by reduced lipid peroxidation (MDA). Overall, liquid Spirulina platensis culture represents a viable functional feed ingredient for common carp, with 10% dietary inclusion providing optimal benefits.