Study of dietary digestible and metabolizable energy to protein ratio on growth performance of rainbow trout (Oncorhynchus mykiss)

The present study aimed to investigate the effects of different digestible and metabolizable energy to protein ratio to obtain optimum ratio in diet. This experiment was carried out with 2600 (control), 2900, 3200, 3500 and 3800 kcal/kg digestible energy (DE) that equal to 2250, 2500, 2750, 3000 and 3300 kcal/kg metabolizable energy (ME) with 35 % protein (CP) in diet. The DE/CP ratios were 74, 83, 92, 100, 108 and for ME/CP 64, 71, 78, 86 and 94. Five treatments were compared in a completely randomized design with 200 fish (average weight 195 ± 5 g) and 4 replicates for 9 weeks. According to the results, the higher growth rate was observed, when the energy to protein ratio increased compared to control group. Fish fed DE/CP=100 (ME/CP=86) dietary content significantly showed the highest weight gain compared to other treatments and improved feed conversion ratio (FCR) and specific growth rate as well (P 0.05). Moreover, fat content significantly increased, but protein content significantly decreased when DE/CP increased (P