Quantifying antimicrobial consumption in the Chilean salmon industry using standardized metrics and indicators: The case of florfenicol and oxytetracycline.

The adoption of standardized metrics and indicators of antimicrobial use (AMU) in the food animal industry is essential for the success of programs aimed at promoting the responsible and judicious use of antimicrobials in this activity. The objective of this study was to introduce the use of standardized AMU metrics and indicators to quantify the use of florfenicol and oxytetracycline in the Chilean salmon industry, and in this way evaluate the feasibility of their use given the type of health and production information currently managed by the National Fisheries and Aquaculture Service (SERNAPESCA), the Chilean agency responsible for regulating aquaculture in Chile. The data available from SERNAPESCA allowed the construction and evaluation of the most data-demanding AMU metrics and indicators. Consequently, the use of florfenicol and oxytetracycline administered by oral and parenteral routes was quantified using the treatment incidence based on both animal defined daily dose (TI) and animal used daily dose (TI). To that end, the study included information from 1320 closed production cycles from farms rearing Atlantic salmon, coho salmon and rainbow trout that were active between January 2017 and December 2021. By applying standardized AMU metrics and indicators, we were able to determine that the median of TI for florfenicol was 75.1 (80 % range, 20.0-158.0) DDDvet per ton-year at risk for oral procedures and 0.36 (80 % range, 0.07-1.19) DDDvet per ton-year at risk for parenteral procedures. For oxytetracycline, the median TI was 3.09 (80 % range, 0.74-42.8) and 0.47 (80 % range, 0.09-1.68) DDDvet per ton-year at risk for oral and parenteral procedures, respectively. The median TI for treatments with florfenicol was 45.6 (80 % range, 10.9-96.5) UDDA per ton-year at risk for oral treatments and 0.28 (80 % range, 0.05-0.80) UDDA per ton-year at risk for parenteral treatments. For oxytetracycline, the median TI was 2.63 (80 % range, 0.61-28.2) UDDA per ton-year at risk for oral treatments and 0.41 (80 % range, 0.08-1.29) UDDA per ton-year at risk for parenteral treatments. This study demonstrates that it is feasible to move from traditional AMU metrics and indicators to standardized ones in the Chilean salmon industry. This is possible because the competent authority requires salmon farms to report detailed health and production information at a high frequency. The use of standardized AMU metrics and indicators can help the authority to have a more comprehensive view of the antimicrobial use in the Chilean salmon industry.