Hitting the road with your horse can trigger significant stress for your equine. Most horses learn to cope with the difficulties of short trips, but long-distance travel can induce a number of adverse behavioral and physiological effects, including elevations in heart rate, decreased fluid intake, loss of appetite, hypocalcemia or hypomagnesemia, weight loss, dust inhalation and coughing, increased levels of plasma cortisol (a hormone that is an indicator of stress), diarrhea, colic, rhabdomyolysis (tying up), and respiratory infections commonly known as "shipping fever" (pneumonia or pleuropneumonia).
Just how seriously horses are stressed when confined to a van or trailer is something we're just beginning to appreciate – thanks in large part to data generated by the 1999 inaugural meeting of the International Workshop on Equine Transport, which was sponsored by the Massachusetts Society for the Prevention of Cruelty to Animals. The workshop, which was assembled largely to address the potential problems involved with shipping horses to the 2000 Sydney Olympics, not only served to identify many of the specific causes of shipping stress, but also to suggest management solutions to help horses cope.
The Workshop concluded that horses get stressed during shipping due to a number of reasons:
Young horses with little previous trailering experience are the most likely to let the stress get to them. Older animals with lots of road miles under their belts usually are better able to take traveling in stride.
Problems Inside the Trailer
One of the biggest problems with most horse trailers is that the ventilation is poor. Dust and mold spores hang in the air along with ammonia and exhaust fumes, and often the air exchange is nonexistent. Then we compound the problem by tying up our horses' heads, which restricts their ability to lower their heads and drain and clear their respiratory passages. As a result, dust, mucus and air pollutants accumulate, causing toxicity and infection in the lower airways.
Studies show that horses confined with their heads elevated for 24 hours develop an accumulation of thick airway secretions and increased numbers of bacteria in the lower respiratory tract, when compared to horses that are allowed to lower their heads. The buildup of bacteria deep in the lungs is presumed to be responsible for the onset of
shipping fever – a catch-all term for infections of the lung that develop from 1 to 4 days after transport, such as pneumonia and pleuropneumonia. Viruses such as influenza or herpes may also spread among horses, and horses can get stressed enough to contract strangles or other opportunistic infections.
Research also has shown that the immune system can become depressed by the stresses of long-distance shipping. One Japanese study of young thoroughbreds showed that during or immediately after a 38-hour, 1,700 km journey, 43 percent of the horses developed a fever. Another study that examined horses that were shipped for 12 hours demonstrated immunity at the cellular level was compromised. Moreover, the immune system didn't bounce back for at least 36 hours after the journey. This suggests that horses require a number of days to recover normal immune response after suffering transport stress. The activities and expectations of horses for 2 to 3 days after long-distance transport (especially if over 5 hours) should be reduced.
There's still much more we don't know about the effects of shipping stress on horses. For example, no-one has yet measured the biological effects of the vibration and jolting of a vehicle on a horse's limbs, or quantified the anecdotal evidence that many horses seem less stressed when allowed to stand backward on a trailer – facing where they've been, rather than where they're going. But we do have ideas about how to minimize some of the harmful effects of shipping. We also don't understand the effects of confinement on the horse, other than the obvious boredom and stress.
Shipping With Less Stress
Try to keep the total travel time under 12 hours. If you have to go further, plan to make overnight stops. Studies have indicated that this should reduce the likelihood that your horse will develop transport-related fever or respiratory disease. Most horses are not stressed by three hours or less of travel.
If possible, stop every three to four hours, for at least 20 minutes or so. If it's safe to unload your horses and let them hand-graze, do so – it will help them clear their nasal passages too. But even standing on the trailer and getting a break from the vibration and the noise is beneficial. Offer water.
Clean the trailer thoroughly before and after each use.
If you can, leave your horse's head untied or loosely tied in a safe way so he can lower his head.
Ensure some airflow in your trailer by opening windows and vents (or, on a two-horse trailer, by leaving the upper back doors open). Horses are more cold tolerant than we are, assuming they are acclimated. A fully closed trailer quickly can become a roasting pan.
Vaccinate your horses against respiratory disease at least two weeks before you begin any long-distance traveling. The new intra-nasal vaccines against influenza and strangles can improve the odds that your horse will stay healthy during and after his journey.
Don't ship any horse that you suspect already is harboring a respiratory infection or has been exposed to other horses who are infected. The stress to his immune system may be enough to send the disease raging out of control.
After any long-distance trip, give your horse a few days to recover before resuming work. For example, if you're shipping to a major competition 14 states away, budget in extra time (2 to 3 days preferably) between your arrival and your first class. Don't expect him to unload and immediately give 100 percent.