Effect of dietary hydrolysate supplementation on growth performance, non-specific immune response and disease resistance of olive flounder (Paralichthys olivaceus) challenged with Edwardsiella tarda

A 9-week feeding trial was conducted to investigate the effects of dietary supplementation with protein hydrolysates on growth, innate immunity and disease resistance of olive flounder. A fishmeal (FM)-based diet was regarded as a control, and three diets were prepared by partial replacement of FM with krill hydrolysate, shrimp hydrolysate or tilapia hydrolysate (designated as Con, KH, SH and TH, respectively). Triplicate groups of fish (24.5 +/- 0.3g) were fed one of the diets to apparent satiation twice daily for 9weeks and then challenged by Edwarsellia tarda. Fish-fed KH diet showed significantly (P<0.05) higher growth performance and feed utilization compared with the Con diet. Dry matter digestibility of the diets was significantly increased by KH and TH supplementation. All the examined innate immune responses were significantly increased in fish fed KH diet. Significantly, higher respiratory burst and superoxide dismutase (SOD) activities were found in fish-fed SH diet. Lysozyme and SOD activities were significantly increased in fish-fed TH diet. However, no significant effect was found on fish disease resistance. This study indicates that dietary supplementation of the hydrolysates, particularly KH, can improve growth performance, feed utilization and innate immunity of olive flounder.