天美传媒

Spirulina supplementation; Nile tilapia; Fish growth performance; Aquafeed; Immunostimulant; Hematological parameters; Natural feed additive; Sustainable aquaculture; Fish health; Microalgae nutrition

Introduction

The global demand for sustainable and efficient aquaculture practices has led to a shift towards natural, plant-based alternatives to synthetic additives and antibiotics in aquafeeds. Among these, Spirulina platensis, a blue-green microalga, has garnered significant interest due to its high protein content (60–70%), essential fatty acids, vitamins, minerals, and bioactive compounds with immunostimulatory and antioxidant properties [1-5]. Nile tilapia (Oreochromis niloticus), a widely cultured species in freshwater aquaculture, is known for its fast growth, feed efficiency, and adaptability, making it an ideal model for dietary intervention studies. This research aims to evaluate the effects of spirulina-enriched feed on the growth performance, hematological indices, and innate immunity of Nile tilapia under controlled experimental conditions [6-10].

Discussion

A total of 240 healthy juvenile Nile tilapia (average weight 10–12 g) were randomly assigned into four dietary groups (60 fish per group, triplicates per treatment) and fed for 8 weeks with the following diets: Control (0% spirulina), Diet A (2% spirulina), Diet B (5% spirulina), and Diet C (10% spirulina). The feeds were formulated using fishmeal, soybean meal, corn, rice bran, and vitamin-mineral premix, with Spirulina replacing a portion of the fishmeal in the experimental diets. Fish were maintained in aerated tanks, monitored for water quality, and fed twice daily to apparent satiation.

Growth performance indicators such as weight gain, specific growth rate (SGR), feed conversion ratio (FCR), and survival rate were recorded biweekly. Additionally, hematological and immunological parameters—such as red blood cell (RBC) count, white blood cell (WBC) count, hematocrit, lysozyme activity, and phagocytic index—were analyzed at the end of the trial.

The results revealed a significant improvement in growth performance in all spirulina-supplemented groups compared to the control. The group fed 5% spirulina (Diet B) achieved the highest weight gain (87% increase) and best FCR (1.2). The 10% spirulina group showed slightly reduced growth compared to the 5% group, possibly due to palatability issues or reduced nutrient digestibility at higher inclusion levels.

Immunologically, spirulina-fed fish demonstrated elevated WBC counts, enhanced lysozyme activity, and improved phagocytic capacity. Diet B (5%) again showed the optimal immunostimulatory effect, indicating that moderate spirulina inclusion can boost innate immunity without adverse effects. Hematocrit and RBC levels also improved significantly, suggesting better oxygen transport and metabolic health. No significant differences were observed in survival rates across groups, and no clinical signs of disease were reported.

These findings confirm spirulina's dual role as a nutritional enhancer and natural immunostimulant. Its active compounds, such as phycocyanin, polysaccharides, and carotenoids, are likely responsible for modulating immune responses. The study also supports the partial replacement of fishmeal, contributing to cost reduction and environmental sustainability.

Conclusion

Spirulina supplementation in Nile tilapia diets significantly improves growth performance, feed efficiency, and non-specific immune responses, with 5% dietary inclusion identified as the most effective level. This natural microalga presents a promising alternative to synthetic additives and antibiotics, supporting both animal health and sustainable aquaculture practices. The adoption of spirulina-enriched feed formulations could benefit small- and large-scale tilapia producers by enhancing productivity and disease resistance without compromising water quality or fish welfare. Further long-term and field-scale studies are recommended to validate these results across different environmental conditions and life stages.

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