Sixteen same-sex pairs of Quarter Horse and Quarter Horse-cross yearlings (8 pairs during each of 2 trials, 1 year apart) were transported for 17.8 +or- 0.52 min over a standard course with one horse facing in the direction of travel and one facing the opposite direction. The orientation of the horses in each trial was alternated with respect to the side of the trailer (float). Heart rates were monitored continuously using a strip chart recorder and were determined for the following events during each trip: after the horses were loaded, but just prior to beginning the trip; immediately after the initial movement of the trailer; during travel over smooth roads near the start and near the end of the trip; before and after an abrupt stop; the mean for the entire trip. During the second trial, plasma concentrations of cortisol and thyroxine (T4) were determined in blood samples taken via jugular puncture in the holding paddock prior to any handling beyond catching, in the trailer prior to hauling and in the trailer immediately after the trip. Observers riding inside the trailer recorded how often the horses impacted the sides and ends of the trailer, lost their balance, pawed, vocalized or defaecated. Rear facing horses had fewer side and total impacts and losses of balance, and thus were better able to maintain their balance during transport. Orientation, side of trailer and sex had no significant effect on any of the heart rates or log transformations of hormone concentrations; however, transport increased cortisol and heart rates overall. All horses' heart rates gradually decreased during the course of the trip. The general stress response elicited by trailering may have masked any treatment effects on heart rate and cortisol. It was concluded that facing horses away from the direction of travel appears advantageous because of their improved ability to maintain their balance.
|Publication Title||Applied Animal Behaviour Science|
|Author Address||Department of Animal Science, Texas A&M University, College Station, TX 77843, USA.|
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