Growth indices, feeding efficiency and survival of rainbow trout (Oncorhynchus mykiss) fed diets containing different levels of Echinacea angustifolia and Origanum majorana extracts

This study was conducted to evaluate the effects of different levels of Echinacea angustifolia and Origanum majorana extracts on growth performance, feed efficiency and survival of rainbow trout (Oncorhynchus mykiss) juveniles. Seven experimental diets with 0 (control), 0.1, 0.2 and 0.4% E. angustifolia and 0.1, 0.2 and 0.4% O. majoranawere prepared. Fish with initial weight 2.6 ± 0.3 g were randomly divided into 7 groups in triplicates and were fed with experimental diet for 4 weeks. At the end trial, the growth parameters, feed efficiency and survival were calculated. Growth and feed indices such as specific growth rate (SGR), Feed conversion ratio (FCR), weight gain, feed efficiency, average final weight, protein efficiency ratio were significantly affected by different levels of plant extracts (P<0.05). Experimental treatments were not significantly affect on condition factor and final length (P>0.05). However, condition factor was higher in fish fed higher levels of plant extracts. No mortality was observed during the experiment. Regression analyses showed relationship between SGR and FCR in fish fed O. majoranaextracts(P<0.05). According to the results of growth parameters and feed efficiency, it can be concluded that dietary 0.2% extract of E. purpurea and 0.1% of O. majorana have growth enhancement effects in this fish.