Homogeneity of an oxytetracycline water medication, administered with a dosing pump

Poster. Oxytetracycline (OTC) is an antibiotic available for water medication in pig farms. This study aims to evaluate if its variable solubility can affect the homogeneity of the medicated solution, when administered with a dosing pump towards drinkers. Indeed, homogeneity is a key factor for drug efficiency. It is also required to respect the maximum residue limits of medicines in meat, and to prevent the development of antimicrobial resistance. A main condition to obtain an homogenous solution in drinkers is to avoid a concentration gradient of medicines in the stock solution tank. Thus, 3 types of tanks commonly used in farms were tested: one without stirrer, one with a propeller and one with a pump mixing the solution. The 3 tanks were filled with a well‐dissolved OTC solution prepared with 55 liters of water mixed with a solvent and an OTC powder on lactose support. Samples were taken at the top, the middle and the bottom of the tanks 4 times during a 24 hour period. OTC concentration was assessed by a colorimetric analysis. Throughout the 24 hour period, the average concentrations of the OTC solution significantly decreased in each tank but this might result from the instability of the OTC color in the time. Indeed, at a given moment, no concentration gradient appeared in the tanks and the solution was quite homogeneous.In order to determine the homogeneity of the medicated solution at drinkers, 2 OTC solutions were prepared, i.e. with or without solvent, and transferred to a tank with a stirrer. Samples were taken at a drinker fixed on a watercourse, reproducing on‐farm conditions. Results show that without any solvent, the OTC solution was not homogeneous, whereas adding a solvent led to an homogeneity level that met the quality requirements of an industrial medicated feed.