Effects of contamination of water with white phosphorus on drinking behavior in sheep

White phosphorus (WP) is a toxic contaminant found in many military training areas. Wild and domestic herbivores may be exposed to WP through drinking contaminated water. Knowledge of how animals react towards WP is important for developing risk assessment models. We investigated if contamination of water with WP affects drinking in domestic sheep. Six young rams were fed hay ad-libitum and given free choice between clean and WP contaminated water (1.5 mg WP/l) in a metabolism pen setup; quantities consumed were registered for three consecutive days (two 1.5 hour sessions per day). Data were analyzed using a linear model. The animals drank significantly more clean (473.1 ± 66.5 g) than contaminated (210.8 ± 46.3 g) water throughout a session. There was no effect of the interaction between treatment and day or between sheep and treatment, indicating that learning did not play any role and that differences in how individual sheep react to WP are negligible. The partial avoidance of WP contaminated water found in this study should reduce the risk of sheep being poisoned while grazing military training ranges; however, the danger of animals consuming particles suspended in water means that the risk is reduced less than the > 50 % reduction in drinking would otherwise imply.