Review: Water medication of growing pigs: sources of between-animal variability in systemic exposure to antimicrobials

Abstract

On many Australian commercial pig farms, groups of growing pigs are mass-medicated through their drinking water with selected antimicrobials for short periods to manage herd health. However, delivery of medication in drinking water cannot be assumed to deliver an equal dose to all animals in a group. There is substantial between-animal variability in systemic exposure to an antimicrobial (i.e. the antimicrobial concentration in plasma), resulting in under-dosing or over-dosing of many pigs. Three sources of this between-animal variability during a water medication dosing event are differences in: (1) concentration of the active constituent of the antimicrobial product in water available to pigs at drinking appliances in each pen over time, (2) medicated water consumption patterns of pigs in each pen over time, and (3) pharmacokinetics (i.e. oral bioavailability, volume of distribution and clearance between pigs and within pigs over time). It is essential that factors operating on each farm that influence the range of systemic exposures of pigs to an antimicrobial are factored into antimicrobial administration regimens to reduce under-dosing and over-dosing.

Levers to Improve Antibiotic Treatment of Lambs via Drinking Water in Sheep Fattening Houses: The Example of the Sulfadimethoxine/Trimethoprim Combination

“…The measurements of water consumption did not reveal any decrease in consumption in the pens at the start of treatment suggesting that the taste of the drug was accepted by the animals. Individual water consumption by pigs is reported to be influenced by numerous factors including stress, boredom, environmental temperature, disease, feed type and constituents and water flow rates [ 18 ], but in our study, despite the same age, weight, environment, food and health status, the individual consumption varied considerably between the lambs. Soraci et al [ 6 ] showed that consumption in healthy animals was also dependent on social rank, even if the effect was lower for water than for feed consumption.…”

“…In this study, the low in vitro solubility of one of the drugs, even after addition of a diluent, excluded it from further experiments. A recent review on water medication reported that this problem of solubility in the stock solution could also occur for other antimicrobial drugs [ 18 ]. In our study, one product was soluble at high concentrations for 2 h at +4 °C in the laboratory and the solution seemed homogeneous in the metering pump with no deposit on the first treatment day but eventually a deposit appeared both in the pump and the drinking troughs as the days went by.…”

“…These different doses probably explain most of the observed inter-individual variability in plasma concentrations but the time-development of drinking behavior of each lamb, with either frequent or infrequent visits to the troughs, could also accentuate this variability. In pigs, one or two peaks of water consumption were observed over each 24-h period [ 18 ]. We also observed a similar trend with two peaks, mainly during daytime, in the lamb population.…”

In-Water Antibiotic Dosing Practices on Pig Farms

“…Several managers described challenges in dissolving these products in dosing pump stock solution containers or header tanks. This was unsurprising, as these three antimicrobials have much lower solubilities in water than other commonly used antimicrobials [21]. Antimicrobials must be fully dissolved and remain in solution at close to the target concentration for the entire dosing period if the prescribed dose is to be ingested, absorbed, and distributed within each pig [22].…”

Evolving technological change in pork production supporting expectations of improved productivity, sustainability and flexibility

“…It is critical to life and must be provided in sufficient quantity and quality to the pig, but clarity on what this means is elusive (Patience, 2013). Little et al (2019) tackle a related topic, namely the use of water as a vehicle by which medications can be provided to pigs at therapeutic levels. This is a topic of growing importance since there is a widespread desire to reduce the delivery of medication via the feed, and water seems to be a logical alternative.…”