The effect of probiotic Bacilli on feed efficiency and carcass quality of rainbow trout, Oncorhynchus mykiss fry

Document Type : Research Paper



In this study, the effects of probiotics bacilli on the feed efficiency and carcass quality in rainbow trout, Oncorhynchus mykiss, fries were studied using a commercial product Protexin Aquatech. A blend of five strains of probiotic bacilli (Basilus licheniformis, B. subtilis, B. polymyxa, B. laterosporus and B. circulans) was used through the supplementation of diets for 60 days. Fish fry with an average weight of 463 ± 32 mg were used. The experimental diets were supplemented with mixture of the five bacilli at concentrations of 1×106 (D1) 1×107 (D2) and 1×108 (D3), (CFU per 100 g food), and a control (probiotics-free diet). The feeding rate was varied between 5 and 8% of body weight. The results indicated that D2 treatment had significantly better growth and feed conversion ratio than the control group and D1 treatment. Results showed that in the experimental treatments, probiotics had a significant positive effect on protein efficiency ratio, lipid efficiency ratio and protein productive value compared to the control treatment (P<0.05). The dry matter, crude protein and crude lipid of fry carcass in D2 treatments, were significantly increased (P<0.05). The results showed that the probiotics bacilli increased feed efficiency and growth performance in rainbow trout fry.