Antimicrobial usage evolution between 2010, 2013 and 2013 in a group of French pig farms

Introduction: Monitoring antimicrobial usage in pig farms is a key element of a reduction plan. The objective ofthis study was to analyse the antimicrobial usage evolution in the same farms between 2010-2013-2016 and to identify the factors of variations.Material & Methods: The study monitored antimicrobial usage in 2016 in 33 farrow-to-finish farms in the West of France. The antimicrobial usage had ever been registered twice for 23 of them in 2010 and 2013 and once for 10 of them in 2013. It was quantified by the number of Course Doses per produced pig per year (nCD/pig). Farmers were asked about the factors that could explain the evolution between 2013-2016.Results: On average, antimicrobial usage significantly decreased over six years (-38%). However, a highvariability of individual evolutions was observed: among the 23 farms with three annual data, 43% decreased their use between 2010-2013 (-3 nCD/pig on average) but had a stable use between 2013-2016 (-0,2 nCD/pig). 26% decreased their use between 2010-2013 (-4 nCD/pig on average) and also between 2013-2016 (-2 nCD/pig). 9% increased then decreased their use during the two periods (+4 then -7 nCD/pig). One farm had the opposite trajectory (-9 then +2 nCD/pig) and another always increased its use (+2 then +5 nCD/pig). Among the 33 farms with data in 2013-2016, 36% decreased their use (-2 nCD/pig on average), 39% had a stable use and 24% increased their use (+3 nCD/pig).Increases were explained by occurrence of sanitary problems (mainly urogenital, digestive and respiratory problems on sows, piglets and fatteners respectively). Decreases were explained by vaccination, stop of preventive treatments and improvement of herd management.Discussion & Conclusion: This study highlights the variability of individual trajectories in antimicrobial usage, due to sanitary issues. It usefully complements the monitoring of average evolution at the country level