Comparison of efficacy of florfenicol with oxytetracycline in reducing mortality due to Yersinia ruckeri infection in rainbow trout (Oncorhynchus mykiss) fry

Objective: The aim of this study was to compare the efficacy of florfenicol (FLO) with oxytetracycline (OTC) to reduce the mortality of rainbow trout fry with ERM disease. Method & Materials: A total of 5,328 rainbow trout fry, weighing 5-6 gram and 7-10cm in the total length were utilized in three separate ponds, with 1,752 fish in the treatment group that received florfenicol medicated feed, 1,859 in the positive control group where they were medicated with oxytetracycline, and 1,717 in the negative or unmedicated feed group. The Flora-Behrood (FLO 10%), oral solution 200ml, (Behrood Pharmaceutical Company) and oxytiline (OTC 20%), water soluble powder (Damloran Pharmaceutical Company) were purchased from the local veterinary pharmacy. flora-Behrood contained 100mg florfenicol/ml. Results & Conclusion: In this study, drug therapy was started with FLO and OTC after diagnosis of ERM disease. The majority of deaths due to ERM disease occurred during the first day of medication (8.82%). The cumulative losses decreased from the 2nd day of medication and reached 7.72%. This value was 0.64% at the end of the treatment period and reached 0.06% at the end of the third days after withdrawal medication. The cumulative losses were 36.50% (29.79% for FLO, 30.00% for OTC and 49.73% for unmedicated group) at the end of the experiments duration. Overall mortality was 522 for FLO group, 558 for OTC group, and 854 for unmedicated group in the experiments duration (figure 8). Mortality was 0.11% for FLO group, 0.69% for OTC group and 1.51% for unmedicated group at the end of the third day of withdrawal medication. In conclusion, this investigation showed that statistical significance in efficacy was found between the two drugs at the end of the third day of withdrawal medication. However, we believe that laboratory studies and additional field studies using florfenicol should be performed before a final recommendation can be made.

Keywords:

Florfenicol , Oxytetracycline , Yersinia ruckeri , Enteric red mouth disease (EMR)