Does oral administration of oxolinic acid or oxytetracycline affect feed intake of rainbow trout?

Short-term oral drug intake was measured in rainbow trout ( Oncorhynchus mykiss) using radioactively labelled diets. In Experiment 1, duplicate groups of trout were fed either a control diet without antibiotic addition, or diets containing either 10 g oxolinic acid (OA) or 10 g oxytetracycline (OTC) per kg. In Experiment 2, triplicate groups of trout were fed diets containing either 1 or 10 g OA per kg. The trout, weighing 200–900 g, were kept in freshwater at 10°C. The fish were accustomed to feeding to satiation every 20 min, 20 h/day; the drugs were fed over a 6-h period. The amount of radioactive feed ingested by the fish was measured directly on anaestherized fish with a portable gamma scintillation counter. The results showed that OA in the diet tended to reduce mean feed intake (mean reduction 17%) compared to controls. This reduction was, however, not significant ( P=0.09). Addition of OTC led to a 61% reduction in feed intake ( P