Use of probiotics to enhance growth, stimulate immunity and confer disease resistance to Aeromonas salmonicida in rainbow trout (Oncorhynchus mykiss)

An 8‐week feeding trial was conducted to evaluate the effects of dietary probiotics on growth, non‐specific immune responses and disease resistance in juvenile rainbow trout, Oncorhynchus mykiss. Fish averaging 5.8 ± 0.8 g (mean ± SD) were fed one of the five experimental diets; one control (Cont), and four other diets were prepared by supplementing single probiotics 1 (Bacillus subtilis; SP1, 0.5%), single probiotics 2 (Bacillus licheniformis; SP2, 0.5%), multi‐probiotics (B. subtilis + B. licheniformis; MP, 0.5%) and oxytetracycline (OTC) at 5 g OTC kg−1 diet. After 8 weeks of the feeding trial, weight gain and specific growth rate of fish fed SP1, SP2 and OTC diets were significantly higher than those of fish fed Cont diet (P