Investigation of the effect of cherry laurel (Laurocerasus officinalis Roem.) dietary leaf extract supplementation on the survival rate, growth performance and some antioxidant enzymes of the rainbow trout (Oncorhynchus mykiss Walbaum, 1792) exposed to oxidative stress induced by high temperature

In this study, the effects of cherry laurel (Laurocerasus officinalis) leaf extract on the growth parameters, survival rate and some antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) of the rainbow trout (Oncorhynchus mykiss) in oxidative stress induced by high temperature were investigated. For this purpose, four studies were performed, one of those is prestudy. In prestudy, the effect of cherry leaf extract supplemented diet in different concentrations (1, 5, 10, 15 g extract/kg) on growth, survival rate and antioxidant enzymes in blood and gill tissue were examined and the optimum concentration was determined as 15 g/kg. In the second study performed in the aquariums, oxidative stress was induced in juvenile rainbow trouts with 3 different water temperatures (15, 19, 21oC). 15 g/kg cherry laurel leaf extract supplemented diets caused growth retardation in 15oC but showed a positive effect on growth in 21 oC. Also, survival rate increased significantly in groups fed with cherry laurel supplemented diets in 19 ve 21oC (p<0.05). In terms of antioxidant enzymes, there were no significant difference between the groups (p>0.05). In the third study performed in an aquaculture facility, the effetcs of 5 g/kg cherry laurel leaf extract supplementation on growth parameters, survival rate and catalase activity were examined but cherry laurel extract in this concentration had no significant effect on the aforesaid parameters (p>0.05). Finally, in the fourth study performed in the aquariums, juvenile rainbow trouts exposed to thermal stress (21oC) were fed with cherry laurel supplemented diets in different concentrations (0, 1, 2.5, 5, 10 ve 15 g extract/kg). As a result, cherry laurel leaf extract decreased feed conversion ratio and increased survival rate significantly (p<0.05). Key words: Cherry laurel, oxidative stress, rainbow trout, survival rate, growth, antioxidant enzyme