Effect of different levels of Spirulina platensis dietary supplementation on the growth, body color, digestion, and immunity of Trachinotus ovatus

The effect of different levels of Spirulina platensis supplementation (0%, 1%, 2%, 3%, 4%, and 5%) on Trachinotus ovatus (initial weight of 5.8 +/- 0.04 g) growth, body color, digestion, and immunity were investigated. The experiment, comprising 3 replications of all supplementation treatments, was performed in 18 cages, 20 fish per cage. The fish were fed twice a day (08: 00 and 17: 00) to satiation over an experimental period of 8 weeks. There was no significant effect of S. platensis dietary supplementation on growth, body composition, and feed utilization in T. ovatus (P>0.05). Abdominal yellow color values markedly increased when feed was supplemented with 3%-5% S. platensis. Dietary S. platensis supplementation had no significant effect on intestinal amylase and lipase activity, while protease activity increased to some extent but was not statistically significant (P>0.05). As the dietary S. platensis levels increased, the content of alkaline phosphatase in the blood also increased, while blood glucose and malondialdehyde (MDA) content in the liver decreased (P<0.05). The MDA content was significantly lower with 3%-5% supplementation than with 0%-2% (P<0.05). S. platensis dietary supplementation can therefore improve body color and immunity in T. ovatus.