Effect dietary energy levels and feeding rates on growth and body composition of fingerling rainbow trout (Oncorhynchus mykiss)

Growth, feed conversion ratio and fillet composition of rainbow trout (initial weight of ۹.۹۹±۰.۱۰۹)were investigated in a ۶x۲ factorial design experiment employing two levels of digestible energy (DE) (۲۹۰۰ and ۳۵۰۰kcal.kg-۱) and six feeding rates (۱.۰%, ۲.۰%, ۳.۰%, ۴.۰%,۵.۰% of the body weight,(BW) day-۱ and to satiation) for ۶۰ days. Specific growth rate (SGR) was highest at ۵.۰% ration in both levels of digestible energy and decreased in the satiation ration. Regardless of feeding rate, rainbow trout grew more by ۳۵% in DE ۳۵۰۰ kcal kg-۱, There was a significant (p<۰.۰۵) interactive effect of feeding rates and DE on weight gain and feed conversion ratio (FCR). The highest FCR was found in fish fed to satiation (۱۹- ۲۱%), while the lowest FCRs, were found in ۴%, ۳% rations in DE levels of ۲۹۰۰ and ۳۵۰۰ kcal kg-۱, respectively. There was a significant increase in protein and fat levels and decrease in moisture content of fish fillet (p<۰.۰۵) as feeding rate and DE increased (p<۰.۰۵). Condition factor increased when feeding rate and DE increased (۱۴-۱۵%). Feeding rate and DE level proved to be the main differentiating factors in growth, FCR and fillet composition parameters. Values of SGR and FCR plotted against feeding rates allowed the optimum and maximum feeding levels to be determined, which were found to be at ۴% and ۳%kcal day-۱ in DE levels of ۲۹۰۰ and ۳۵۰۰kcal kg-۱, respectively, for the rainbow trout of ۱۰۹average weight. 

Keywords:

Rainbow trout , Nutrition , Feeding rate , Feed energy