Effect of prophylactic chloramine-T treatment on growth performance and condition indices of rainbow trout (Oncorhynchus mykiss)

Chloramine-T is a commonly used therapeutic agent for the treatment of bacterial gill disease and related phenomena in the salmonid aquaculture industry. There is little known about its effects on healthy fish. Using a 24-tank replicate growth assay system, rainbow trout (Oncorhynchus mykiss) (average weight 98 g) were exposed twice weekly to chloramine-T at 10 mg/L for 1 hour, throughout an 11-week growth trial and compared to matched controls. Fish were fed ad libitum without feed wastage to assess appetite and feed conversion. Growth parameters were assessed every 3 weeks, at the end of weeks 3, 6, 9, and 11. Chloramine-T treatment was not associated with either clinical disease or mortality. Final weight and specific growth rate were significantly impaired during the growth trial in the groups of fish treated with chloramine-T compared to controls. This was attributed to a significant depression of feed conversion efficiency and to a minor depressison in appetite in treated fish.