Phycocyanin from Spirulina platensis promotes growth, immunity, and resistance to Vibrio parahaemolyticus in shrimp

Abstract

Objectives: The present study evaluated whether dietary phycocyanin extracted from Spirulina platensis could improve growth performance, feed utilization, intestinal microbial balance, immune response, antioxidant status, and resistance to Vibrio parahaemolyticus infection in Pacific white shrimp (Litopenaeus vannamei). Methods: A feeding experiment was conducted for 70 days using 240 shrimp randomly assigned to four dietary treatments with three replicates each. Experimental diets included a control diet without supplementation and diets supplemented with phycocyanin at 0.1, 0.2, and 0.3 g/kg diet. Growth indices, feed efficiency, intestinal bacterial populations, immune parameters, antioxidant enzyme activities, and the expression of selected immune- and antioxidant-related genes were analyzed. At the end of the feeding period, shrimp were challenged with Vibrio parahaemolyticus to evaluate disease resistance. Results: Shrimp receiving phycocyanin-supplemented diets showed significantly better growth performance and feed utilization than the control group. Improvements were also observed in survival rate and intestinal microbial composition, with higher counts of beneficial bacteria and lower counts of harmful microorganisms. Dietary supplementation enhanced immune responses, as indicated by increased lysozyme and prophenoloxidase activities. Antioxidant enzyme activities, particularly catalase and superoxide dismutase, were significantly elevated in supplemented groups. In addition, the expression levels of immune- and antioxidant-related genes were upregulated in shrimp fed phycocyanin-containing diets. Following bacterial challenge, supplemented groups exhibited lower mortality rates than the control group, with the strongest protective effect observed at the highest supplementation level. Conclusions: The findings indicate that phycocyanin derived from Spirulina platensis can serve as a beneficial dietary supplement for Litopenaeus vannamei. Supplementation improved growth, supported intestinal microbial stability, enhanced immune and antioxidant responses, and increased resistance to Vibrio parahaemolyticus infection. These results suggest that phycocyanin may represent a useful natural feed additive for sustainable shrimp aquaculture.