Effect of different diets on growth performance in rainbow trout, Parasalmo mykiss (Walbaum, 1792)

The present study aimed to evaluate the effect of various diets on growth performance in rainbow trout, Parasalmo mykiss (Walbaum, 1792). The eight months feeding experiment in fish farm in Ladoga lake (Republic of Karelia, Russia) was conducted to investigate the effects of different diets on growth rate in three genetically similar and homogeneous groups of juvenile rainbow trout aged 1+ (initial body weight, 110 g). Three commercial diets often used in fish farms in the North-West region of Russia and with different levels of protein and structural lipids and fatty acids were used. From March to November groups 1 and 2 were fed commercial diets 1 and 2, respectively. In late June group 2 was randomly divided into two groups (groups 2 and 3). Group 2 was continued to feed diet 2 when group 3 was fed diet 3. The contents of dietary protein, lipids and fatty acids were analyzed. In addition, at the third week of each month of experiment the body weight, body length and mortality of fish were measured (50 fishes from each group). The dynamic of growth in length and weight of rainbow trout was depended on the fish feeding schedule. Weight gain and growth rate in three groups of fish were different. The overall results of this study established that feeding a diet with high level dietary protein, structural lipids (phospholipids, cholesterin) and ω3 polyunsaturated fatty acids (diets 1and 3) leads to high growth rate of rainbow trout (groups 1 and 3, respectively).