Using possibilities of gren tea (Camellia sinensis) as immunostimulant in rainbow trout (Oncorhynchus mykiss) culture

The present study was conducted to evaluate the effect of dietary inclusion of green tea leaves, Camellia sinensis, on growth performance, feed utilization, body composition, hematological parameters and serums biochemical immune parameters on rainbow trout, Oncorhynchus mykiss. A total of 546 rainbow trout with an average body weight of 40.4±0.01 g were divided in the seven experimental treatments (three replicates each). The fish were fed diet containing 0% (control/diet1), 0.25% (diet 2), 0.5% (diet 3), 1% (diet 4), 2% (diet 5), 3% (diet 6) of dried green tea leaves (GTL) containing 5.3±0.04% epigallocatechin gallate-3-gallate (EGCG) and 1% green tea leaves dust (GTLD) (diet 7) containing 6.5±0.07% EGCG for 60 days. After 60 days of the feeding trial, fish fed diet 2 had higher weight gain (WG), specific growth rate (SGR), apparent net protein retention (ANPR), and protein efficiency ratio (PER) than other groups, had a lower feed conversion ratio (FCR) than other groups, but not significantly changed than control group (P > 0.05). At the end of the experiment, WG, SGR, protein consumption (PT), PER and ANPR was calculated statistically similar in all groups and the control group (P > 0.05). Fish fed diet 6 had lower WG, SGR and PER than control, and FCR higher than control (P < 0.05). Crude lipid content of liver and fillet in all groups were significantly lower than the control group (P < 0.05). At the end of the experiment, blood serum parameters: total protein (TP), albumin (ALB), globulin (GLB), glucose (GLU), total cholesterol (CHO), triglyceride (TRIG) and the parameters of immune serum: lysozyme activity (LYZ), myeloperoksidaz (MPO) and the total immunoglobulin (IG) parameters did not show a significant change in all groups compared to the control group (P > 0.05). White blood cell (WBC) values of fish fed with diet 4, 5 and 6 and red blood cell (RBC) values of fish fed with diet 5 and 6 were statically lower than control (P < 0.05). These results showed that administration of GTL especially at 0.5% level in rainbow trout diet enhanced the growth performance and fed utilization even though these parameters were not significantly affected by the experimental diets except for 3% GTL group. Administration of 1% dose of GTLD and GTL especially at higher doses (e.g. 3%) in the experimental diets showed hypolipidemic effects for rainbow trout.