The effects of diets containing hazelnut meal supplemented with synthetic lysine and methionine on development of rainbow trout (Oncorhynchus mykiss Walbaum, 1792)

This study was conducted in order to investigate the effects of diets, including hazelnut meal supplemented with synthetic lysine and methionine, on development of rainbow trout (Oncorhynchus mykiss Walbaum, 1792) which are commonly cultured in Turkey and the World.In the research, six different isonitrogenous (46 %) and isocaloric (21 kJ/g) test diets were prepared. One of them was a fish meal based on control diet and the others were test diets containing hazelnut meals with the increasing percentages as follows: 10 % (FK1), 20 % (FK2), 30 % (FK3), 40 % (FK4) and 50 % (FK5). In order to balance lysine and methionine of the test diets as much as possible, synthetic lysine and methionine were added to each test diet except the control diet which was based on the lysine and methionine content of the control diet. Rainbow trouts with an average weight of 114.16±0.03 g were stocked in three replications for each group and fed with test diets twice a day to apparent satiation for 60 days.At the end of the research, the highest weight gain of all groups was obtained from FK4 group (304.28±6.50 g), which was a statistically significant (P<0.05) difference among the other groups. There were no statistically significant differences among groups in terms of specific growth rate, relative growth rate, feed conversion ratio, protein efficiency ratio and productive protein value; however, the best values were obtained from FK4 group (P? 0.05). The results showed that the protein digestibility rate was not affected from the hazelnut meal ratio in the diet while the total digestibility and lipid digestibility rates were decreased with respect to the increase of hazelnut meal ratio in the diet to 50 % (P<0.05).This research has shown that the hazelnut meal supplemented with synthetic lysine and methionine could be best used at the rate of 40 % in rainbow trout diets without any negative impact on growth performance, nutrient digestibility and body composition.