Effect of Feeding Frequency and Romet-Medicated Feed on Survival, Antibody Response, and Weight Gain of Fingerling Channel Catfish Ictalurus punctatus after Natural Exposure to Edwardsiella ictaluri

Abstract The efficacy of restrictive feeding regimes and Romet®-medicated feed (formulated at 40.5-mg Romet-30 premix/kg feed) fed at 2.0% body weight was evaluated under field trial conditions for the treatment of naturally induced Edwardsiella ictaluri infections in fingerling channel catfish. After detection of an Edwardsiella ictaluri epizootic, fish were fed medicated and non-medicated feed every day, every other day and every third day for the duration of the experiment. In addition, experimental treatments also included fish that were completely withheld from feed and those provided Romet-medicated feed for five consecutive days followed by non-medicated feed fed daily. Feeding frequency and diet significantly affected survival and weight gain. Survival was greatest among fish that were completely withheld from feed or that were fed medicated feed every other or every third day. The use of non-medicated feed every other or every third day was equally as effective for reducing Edwardsiella ictaluri associated mortalities as feeding Romet-medicated feed on a daily basis. Feeding fish Romet-medicated feed for five consecutive days was not an effective treatment. Agglutinating antibody titers against Edwardsiella ictaluri were significantly lower in all groups of fish fed Romet-medicated feed for the duration of the experiment. These data indicate that feeding frequency is a primary factor affecting the severity of Edwardsiella ictaluri infection and that prolonged consumption of Romet-medicated feed may suppress antibody production.