Growth, hematological, innate immune responses of Mugil cephalus fed with Echinacea purpurea-supplemented diet against Photobacterium damselae infections

This study was conducted to evaluate the effects of Echinacea purpurea leaf extract on growth performance, biochemical and hematological indices and non-specific immune responses of Mugil cephalus fingerling against Photobacterium damselae. A basal diet was supplemented with 0 (control), 50, 100 and 200 mg purple coneflower extract (PCE) kg⁻¹ to formulate four experimental diets. Each diet was randomly allocated to triplicate groups of fish with an initial average weight of approximately 0.75 g. After 60 days of feeding trial, fish fed diets with 100 and 200 g PCE kg⁻¹ showed a significant (P < 0.05) increase in final weight, food intake, daily growth rate and efficiency of protein compared with control treatment. There were significant differences between biochemical parameters (serum total protein content, albumin content, globulin content and albumin-to-globulin ratio) and hematological indices (RBC, WBC and HB) in the fish fed with 100 and 200 mg PCE kg⁻¹ compared with fish fed with 50 mg PCE kg⁻¹ and control treatment (P < 0.05). The highest lysozyme activity and phagocytic and respiratory burst activity were observed in fish fed with 200 mg PCE kg⁻¹. In addition, PCE decreased mortality in M. cephalus in a dose-dependent manner after challenge with P. damselae. The results suggest that E. purpurea administration at 200 mg PCE kg⁻¹ exerted positive effects on growth, biochemical and hematological indices and immune responses in M. cephalus and that the mortality percentage could be remarkably reduced after challenging the fish against P. damselae.