Ineffectiveness of amoxicillin delivered in drinking water for treating respiratory pathogens in pigs: does dosing based on peak of water consumption improve exposure and treatment efficacy?

Reducing antibiotic use in veterinary medicine is a key strategy to fight antimicrobial resistance. In France, antibiotic consumption in pig production decreased by 67% between 2011 and 20221. Nevertheless, post-weaning piglets remain frequently treated, including with amoxicillin for systemic and respiratory infections like Streptococcus suis, Actinobacillus pleuropneumoniae, and Pasteurella multocida2. Collective oral treatments, administered via feed or drinking water, are common in pig farms for treating large group of animals at the same time. Even so, this route of administration has been identified as posing a high risk of resistance selection, although this risk is lower via drinking water3. Drinking water treatments are therefore still widely used as they offer greater flexibility than medicated feed, even if intra- and inter-individual variability in drug exposure is inherent to collective oral treatments4. Variability in drug exposure arises from preparation errors, drug properties, pharmacokinetic (PK) interindividual variability, and drinking behavior could also be affected for example by age, weight, social hierarchy and environmental conditions5. To quantify the impact of these factors on antibiotic plasma concentrations in piglets, and therefore on the efficacy of antibiotic treatments administered via drinking water, we developed a pharmaco-statistical model based on individual water intake data from 150 post-weaning piglets treated with amoxicillin in an experimental farm. We merged these water consumption data with amoxicillin PK parameters and observed plasma amoxicillin concentrations to compare three treatment modalities via drinking water: a classical continuous treatment and two timerestricted treatments with a concentration of the dose over daytime or night-time.