Effects of dietary ginger (Zingiber officinale) extract and curcumin on growth, hematology, immunity, and antioxidant status in rainbow trout (Oncorhynchus mykiss)

The use of dietary ginger (Zingiber officinale) and curcumin as immunostimulants is a promising method in fish culture. This study evaluated the impacts of dietary ginger extract and curcumin on growth, hematology, immune and antioxidant status, and expression of some growth and immune related genes in rainbow trout (Oncorhynchus mykiss) fingerlings. Fish (7.5 ± 0.1 g) were randomly distributed into 12 fiberglass tanks (30 fish per tank), divided into four treatments in triplicate and received no supplementation (control) and diets supplemented with 0.5% ginger extract (ginger treatment), 0.5% curcumin (curcumin treatment), and 0.5% ginger extract plus 0.5% curcumin (mix treatment). The growth of fish and muscle crude protein content were highest in the mix treatment. Higher protein efficiency ratio, hemoglobin, and plasma ALP activity were observed in fish fed supplemented diets than the control. Red blood cells (RBC) counts and hematocrit value were higher in the ginger treatment, then curcumin and mix treatments and lower in the control. White blood cells (WBC) counts and plasma lysozyme, ACH50, catalase, and SOD activities were highest in fish fed the mix diet. Moreover, plasma C4 value and GPx activity were significantly higher and triglyceride value was lower in the curcumin and mix treatments compared to the control and ginger treatments. The highest plasma C3 and total immunoglobulin (Ig) values were found in fish fed curcumin and mix diets, but those were not significantly different from the ginger treatment. Growth hormone (GH) and lysozyme relative expression levels were highest in fish fed the mix diet and lowest in the control. Thus, the combination of 0.5% ginger extract and 0.5% curcumin (mix diet) to improve growth, body composition, hematology, immune responses, and antioxidant status in rainbow trout can be recommended. •Fish growth was highest in the combination of ginger extract and curcumin (mix) treatment.•Catalase, SOD, lysozyme, and ACH50 activities and WBC counts were highest in the mix treatment.•The combination of 0.5% ginger extract and 0.5% curcumin (mix diet) can be recommended for feeding of rainbow trout.