Dietary Olextra enhances disease resistance and hypoxia tolerance in juvenile Pacific white shrimp ( Litopenaeus vannamei )

Olextra, a processed hydroxytyrosol-rich olive pomace, is a by-product of olive oil industry and can be applied as a feed additive to improve shrimp health. This study aimed to evaluate the effect of Olextra on the growth, resistance to Vibrio parahaemolyticus infection, and tolerance to hypoxia of Pacific white shrimp. Shrimp were fed Olextra for 45 days and then challenged with Vibrio parahaemolyticus and hypoxic conditions for seven days. Shrimp fed 0.3% Olextra had a survival rate of 89.38%, which was significantly higher than the control (79.06%) although their body weight and FCR were not significantly different from the control. Vibrio spp. counts of shrimp fed 0.3% Olextra were significantly reduced in the hepatopancreas and intestines. The survival rate of shrimp fed 0.3% Olextra and challenged with V. parahaemolyticus or hypoxic stress was significantly improved. In summary, 0.3% Olextra could enhance shrimp resistance to V. parahaemolyticus infection and hypoxic conditions.