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Horses’ Response to 24 Hour Travel StudiedBy Kentucky Equine Research Staff · October 20, 2004
It is generally understood that transportation is stressful to horses. This study was designed to measure the changes in various manifestations of stress during a 24-hour ride in a commercial horse van, and to quantify degree of recovery 24 hours after the trip.
How was the study conducted?
Fifteen adult horses were used in the study. Ages ranged from 4 to 18 years and weights were between 1036 and 1401 pounds. Several breeds including Thoroughbred, Saddlebred, Hackney, Paint, and Warmblood were included. High temperature during transport was 100*F and low temperature was 73*F. Relative humidity was between 22 and 58%.
All horses were being used in a university riding program and had some experience with transport prior to being included in the study. To familiarize them with the vehicle and loading procedures, the horses participated in practice loadings onto the study van a week before the trip.
Measurements of body weight were taken twice a day for two days before and one day after the trip. Blood samples were taken five times a day for two days before travel, on the day of the trip, and the following day. The samples were analyzed for measures of stress, dehydration, muscle damage, and general health.
Travel was mostly on interstate highways. The horses were cross-tied in individual stalls with either straw or shavings used for bedding. Alfalfa hay was always available, and buckets of water were offered periodically throughout the travel period.
What results were found?
The researchers reported that horses did not begin to drink measurable amounts of water until they had been traveling for six hours. Total water consumption by individual horses varied from 4.3 to 7.9 gallons during the 24-hour travel period. This level of water consumption is below the average for horses in a hot climate.
On the day of travel and the first day post-travel, measurements of cortisol and ratios of neutrophils to lymphocytes were in ranges indicative of stress. Hematocrit measurements indicated varying degrees of dehydration. Muscle metabolite parameters (concentrations of lactate, creatine kinase, and aspartate aminotransferase) showed that horses had performed a significant level of work. Body weights immediately after unloading were decreased by an average of 6.1% over pre-trip weights. All horses were then given three hours of free access to water, after which weights were again recorded. The average weight had increased, but after 24 hours, weights had still not returned to pre-trip levels.
Two of the 15 study horses exhibited mild colic signs within three hours after unloading. These horses were monitored for several days during which they showed elevated temperatures and signs of respiratory infection. Younger horses showed more nervous behavior than older horses, and the authors suggested this was related to increased travel experience among the older horses.
What does this study tell us about managing transported horses?
The authors explained that, because parameters vary over the course of 24 hours, it may be helpful to track things like body temperature and weight at several times throughout the day for several days before a trip. Recording these variations will allow post-trip measurements to be compared to measurements taken at similar times, giving the owner a more accurate way to evaluate the impact of transport on a particular horse.
The method of transportation used in this study (commercial vans traveling interstate highways) provided a smoother ride with fewer changes in speed and direction than what would be experienced by horses riding in smaller trailers in city traffic or on secondary roads. Frequent or sudden stops, starts, and turns will add to fatigue and stress, even on brief trips.
Additionally, the authors pointed out that long periods of travel in hot weather elicit responses that indicate stress, dehydration, muscle metabolism alterations, and lowered effectiveness of the immune system. These changes may take more than 24 hours to return to normal. Owners and riders should take these factors into account and allow horses time for rest and recovery before asking them to train, race, show, or perform other strenuous exercise. Horses should be monitored closely for digestive or respiratory illness for several days after transport
The study “Physiological responses of horses to 24 hours of transportation,” was conducted by CL Stull (University of California, Davis) and AV Rodiek (California State University, Fresno.)
