Effect of animal density and trough placement on drinking behavior and dehydration in slaughter horses

One of the issues in the debate over the regulation of the transport of horses to slaughter plants is whether slaughter horses will consume water on board the trucks in which they are transported. The effect of horse density and trough placement on latency to drink and the amount of time spent drinking water on-board a semi-trailer were determined in three experiments using 19, 20, and 24 slaughter-type horses. The horses were deprived of access to feed and water for four hours prior to and for eight hours during transportation. Transport in a commercial 16-m long, single-deck, open-topped semi-trailer commenced at 1200 h and lasted until 2000 hours, followed by a one-hour watering period. In Experiments 1 and 2, the trailer was divided into four 2.4×3.6-m compartments into each of which two steel water troughs (25×90 cm) were hooked on the inside of the trailer after transportation ended and immediately prior to the watering period. Each compartment contained four to six horses. The troughs were placed along one side of the trailer in Experiment 1 and placed on opposite corners of each compartment in Experiment 2. In Experiment 3, the trailer was divided into two 2.4×7.2-m compartments each containing 12 horses and two troughs were staggered on the opposite walls of each compartment (four troughs per compartment). Three of the 19 horses were blocked from drinking by other horses in Experiment 1, five of the 20 horses were blocked from drinking in Experiment 2, and all horses drank in Experiment 3. All horses that drank initiated their first drink within 15 minutes of water entering the troughs in Experiments 1 and 2 and within 25 min for Experiment 3. Total serum protein, Na, and Cl were not significantly different between trough placements (Exp. 1 and 2) (P>.52) or between densities in Experiments 1 and 2 (P>.16). The larger compartment (2.4×7.2 m) and group size (12 horses) in Experiment 3 provided adequate maneuvering room so that all of the horses could get access to water when the water troughs were placed on both sides of a compartment at .8m of trough per 2.4 m of wall. Providing slaughter horses with access to water onboard trucks appears to be a useful method of reducing dehydration.