Effect of Drinking Water Distribution System Design on Antimicrobial Delivery to Pigs

Abstract

On many pig farms, growing pigs are mass-medicated for short periods with antimicrobial drugs through their drinking water for metaphylaxis and to treat clinical disease. We conducted a series of four prospective observational cohort studies of routine metaphylactic in-water antibiotic dosing events on a commercial pig farm, to assess the concentration of antimicrobial available to pigs throughout a building over time. Each dosing event was conducted by the farm manager with a differently designed looped water distribution system (WDS). We found that the antimicrobial concentration in water delivered to pigs at drinkers in each pen by a building’s WDS over time was profoundly influenced by the design of the WDS and the pigs’ water usage and drinking pattern, and that differences in the antimicrobial concentration in water over time at drinkers throughout a building could be eliminated through use of a circulator pump in a looped WDS. We also used a hydraulic WDS modelling tool to predict the antimicrobial concentration at drinkers over time during and after a dosing event. Our approach could be used to evaluate alternative in-water dosing regimens for pigs in a specific building in terms of their clinical efficacy and ability to suppress the emergence of antimicrobial resistance, and to determine the optimal regimen. The approach is applicable to all additives administered through drinking water for which the degree of efficacy is dependent on the dose administered.

Water Distribution Systems in Pig Farm Buildings: Critical Elements of Design and Management

“…We recently conducted four on-farm studies of the effects of WDS design on antimicrobial delivery to pigs that described the hydraulic performance of looped WDSs in two pig buildings with the main pipes of 50 mm internal diameter that were greater than 200 m in length [8]. The two buildings were located on a farm that participated in the survey reported here.…”

“…Furthermore, when an over-sized WDS is used to administer additives to a group of pigs, its large holding volume relative to pigs' daily water demand and very-low-water-velocity water flows through pipe sections may lead to large differences between drinkers at varying distances along the building's WDS from the dosing pump in (1) the initial lag after commencement of dosing, before the additive first reaches the drinker, and (2) the duration over which the additive is available at the drinker. This results in between-animal variability among the group of pigs in the quantity of the additive ingested over time, and, for additives that are absorbed from the digestive tract, the systemic exposure to them [8].…”

“…Water flow through the building's WDS is very dynamic. Flow rates within each pipe section and the residence time ('age') of water at each drinker may change markedly from hour to hour each day, depending on characteristics of the WDS and pigs' water demand, which is a function of the number of pigs in the building, their bodyweight, and their drinking patterns [8]. Important design characteristics of a WDS are its configuration (looped or branched); the length, diameter, and smoothness of the internal surface of each section of pipe; the system's head pressure; and the number of bends and constrictions or expansions in the diameter of pipes along the system, which result from the use of fittings [9].…”

“…A water-soluble antimicrobial product may be administered into a building's main water line through a proportional dosing pump or header tank, and the hydraulic performance of the building's WDS determines the time course of antimicrobial drug concentration in water available to pigs at drinkers in each pen during and after the dosing event. Differences in the antimicrobial concentration in water delivered to pigs at drinkers in each pen over time by the WDS are a source of between-animal variability in the in-water dosing process and may affect the number of pigs that have systemic levels of the antimicrobial that are sufficient to successfully eliminate or substantially reduce numbers of the target pathogen and achieve high clinical efficacy, while minimizing selection for and propagation of resistant pathogens [8,14,15].…”

Qualitative risk assessment of homogeneity, stability, and residual concentrations of antimicrobials in medicated feed and drinking water in pig rearing

“…The homogeneity and stability of the drug in medicated feed and medicated drinking water must be assured until the moment of intake by the animals. The residual concentrations or in other words the remaining concentrations of the antimicrobial drug in feed or water after the end of treatment, and the homogeneity and stability of medicated feed and medicated drinking water is likely to be influenced by a) the methods used for preparing, transporting, and storing medicated feed and drinking water [25], b) the materials used to construct the feed and drinking water pipelines and their design [26][27][28][29], c) the number of treatment days [7], d) the pharmaceutical formulation used [30,31], and e) the cleaning protocol of the pipelines [2]. Human errors when preparing and administering the medication may also occur if the medication is prepared at the farm instead of bought from a Good Manufacturing Practices (GMP)-certified feed manufacturer [32,33].…”