Spirulina is a fast-growing cyanobacterium receiving much attention because of its high levels of proteins, vitamins, antioxidant-quality pigment fatty acids, and antimicrobial properties as a supplemental protein and other nutritional sources. Spirulina platensis and S. maxima are two major species used in aqua feed. The spirulina meal might be useful to enhance the growth and also improve the immune response in rainbow trout.
The aim of the study was to evaluate the effects of Spirulina platensis on the growth performance, feed utilization, immune response, and, skin pigmentation of rainbow trout. A total of 120 fish with an average weight of 17 ± 2 g were divided into four groups (3 experimental groups with diets containing 2.5%, 5%, and 7.5% spirulina, and a control group). The four diets were fed for 12 weeks at satiation level. All the data were subjected to one-way ANOVA using R programming.
Results revealed significantly the highest growth performance was found in in the group fed 7.5% Spirulinacompared to other groups. Immune markers showed that C3, IgM, and lysozyme levels were significantly higher in the 7.5% group, whereas C4 levels remained unaffected. Skin pigmentation, measured by β-carotene concentration, increased significantly in fish fed 7.5% and 5% Spirulina, enhancing skin coloration.
The study highlighted Spirulina’s potential as a growth enhancer and immune stimulator, attributing its effects to β-carotene and other pigments such as C-phycocyanin. Additionally, Spirulina promoted better carotenoid absorption in fish skin, improving pigmentation. These results suggest that including Spirulina at 7.5% in fish diets can maximize benefits in aquaculture by enhancing fish health, growth, and marketability.