Effects of intermittent hydrogen peroxide exposure on growth and columnaris disease prevention of juvenile rainbow trout (Oncorhynchus mykiss)

Twice-weekly treatment of juvenile rainbow trout with hydrogen peroxide at 200 mg/litre for 1 h was effective in limiting the degree of fin and epithelial damage associated with an experimental thermally promoted outbreak of columnaris disease attributable to Flexibacter columnaris [Cytophaga columnaris]. The treatment was at least as effective as a comparable treatment with chloramine-T. The treatment also altered fish growth patterns. During a 7-week growth trial, disease-free treated and untreated fish had similar growth rates, feed consumption, and conversion efficiency. However, during the first 3 weeks, treatment suppressed growth through inhibited conversion efficiency. During the final 4 weeks, treated fish entered a compensatory growth phase marked by significantly increased growth and appetite compared with controls and recovery of conversion efficiency to match controls. Gills from treated fish were no different to those in control fish at the end of the trial..