Sue McDonnell, PhD, Certified Applied Animal Behaviorist, was preparing a horse for long-distance transport. Getting the horse from her home base at the University of Pennsylvania's New Bolton Center to his final destination involved a jostling trailer ride to the airport, then a cross-country flight. Compound that with separation from his stablemates, a disruption of his normal feeding schedule, and having to adapt to his new environment, and the horse was under considerable stress.
"Every time we put a horse on a trailer, I'm amazed at how well they do and how much we expect from them," said McDonnell, who is the founding head of the Equine Behavior Program at the University of Pennsylvania School of Veterinary Medicine. The horse on the move is exposed to nearly every factor recognized as a potential stressor for horses. Each one has the potential to make him vulnerable to a myriad of physical ailments, from respiratory infections to gastric ulcers.
But horses needn't be in extreme circumstances such as long distance travel to experience stress. Extreme hot and cold climate conditions, training regimens, dietary or feeding schedule variations, general daily routine disruptions, injuries, and changes in social interactions with other horses and humans can all represent equine stressors.
According to Carey Williams, PhD, equine management specialist and assistant director of the Equine Science Center at Rutgers University, horses' very nature makes them particularly sensitive to stressful situations. As prey animals, horses are genetically hard-wired with a "fight or flight" response nervous system that physio- logically allows them to turn on a dime in the presence of danger--either real or perceived. Under stress, a horse's endocrine glands flood his body with adrenaline and cortisol--the so-called "stress hormone" also present in humans--and his heart rate increases. While all that is happening on the inside, horses outwardly display a stressful state by swishing their tails, pawing the ground, bucking, kicking, biting, or fleeing the troubling factor altogether.
Evolution equipped horses with their fight or flight responses to keep them safe from predators or other threats in the wild. These days it's the realities of domestic life that stress horses.
According to Williams, studies show that 80-90% of all racehorses, 60% of all performance horses (including eventers, jumpers, and Western performance horses), and 30-40% of dressage horses develop gastric ulcers during the normal course of their careers.
"That's because we force our horses to live their lives at our convenience and on our schedules," says "Williams. "We put them on training schedules to meet our goals, allow them to spend less time in the pasture being horses, and feed them on a schedule that's convenient for us."
In fact, what horses eat and when they eat play a significant role in promoting equine stress. Horses' physiology makes them vulnerable to gastric ulcers because their stomachs secrete acid constantly, even when they are not eating or digesting food. The roughage horses consume when they graze or eat hay in their stalls absorbs acid and promotes saliva production, both of which work to neutralize stomach acid. However, horses' stomach acid spikes when they ingest grain, thanks to an increase in gastrin, a hormone that stimulates stomach acid production. Horses are most likely to develop ulcers when forage--either pasture or free-choice hay--is scarce, after weaning, or while acclimating to a new barn or training environment.
Veterinarians can insert an endoscope (a flexible tubular instrument for visualizing the interior of an organ or part) into a horse's stomach to accurately diagnose equine ulcers. But the invasive procedure is performed only after horses present common ulcer-related clinical signs.
Dull coat, weight loss, bouts of colic, and a change in attitude can all be signs that a horse is suffering from ulcers.
"Horses (with ulcers) get picky about food," says McDonnell. "When they do eat, they eat less vigorously. Some horses even become aggressive over their food when they have ulcers."
Treating ulcers involves reducing horses' grain intake and feeding hay rich in alfalfa and clover. According to Sarah L. Ralston, VMD, PhD, Dipl. ACVN, associate professor in the Department of Animal Sciences at Rutgers University, both alfalfa and clover are high in calcium, which absorbs excess stomach acid in horses and humans.
"It's like taking a Tums," Ralston says. "People who suspect their horses have ulcers should get them used to eating the legume-based feeds."
Sometimes it takes more than diet and stress reduction to cure equine ulcers. Sometimes it takes medication such as omeprazole (GastroGard). But reducing stress is key. "Just like people, you can feed a good diet, but you have to remove the stress for the ulcer to heal," Ralston says.
Stress and Immunity
Ulcers aren't the only stress-related health threats to horses. Long-term exposure to stress suppresses horses' immune systems, alters their metabolic rates, and can promote personality changes, including aggressiveness and depression.
"The definition of prolonged stress exposure is that the horse cannot adapt to the stress and becomes clearly agitated," Ralston says. "And there's a difference between stress and distress."
Distressed horses exhibit behaviors such as nervousness and aggression, extreme irrational anxiety, excessive snorting, and inordinate sensitivity to noise. The threshold between stress and distress varies from horse to horse.
"The way to help a horse in distress is to determine why the horse is being stressed out," Ralson says. "And that also varies from horse to horse."
Although every horse has some stress in his daily life, horses' stress levels are more likely to rise in connection to specific activities or life changes. Foals exhibit signs of stress at weaning, says McDonnell. "Their diet's changing from mares' milk to hard feed at the same time they're experiencing social and separation stress," she says.
Horses also experience stress when they're in training. And unlike the temporary stress of early life, training-related stressors occur throughout a horse's lifetime. That's because horses must process new information and adapt to new performance standards every time they're asked to master new skills or perfect old ones.
"Horses learn a lot like little children learn when they are nonverbal," McDonnell says. "One of the big hurdles is learning to learn."
According to McDonnell, horses "learn to learn" when they understand they will be asked to perform a certain behavior one day and master a new behavior the next.
"Until they get to that point, training can be very stressful," McDonnell says.
Patience is key to minimizing training-related stress, and that frequently means giving horses in training regularly scheduled breaks when they exhibit training-fatigue behaviors. "Horses will stop making training progress when they're under stress," says Williams. "That's when owners should give them a season, or a month, or even just a couple of days off."
Williams also prescribes patience when owners acquire a horse or remove it from a familiar barn. "Adapting to a new environment can be very stressful for horses," she says. "They miss stable- and pasturemates and even their caretakers, and they need time to acclimate."
Relocating hay and feed along with the horse can blunt some of the transition stress. Beyond that, Williams warns owners to lower their short-term expectations. "Don't expect too much in terms of performance or training the first week," she says. "Also, don't ride the first few days. Instead, take the horse out of his stall, groom him, walk him around, and let him look around to get used to his new surroundings. Don't push it."
The advice is the same when pastured horses must be indoors for extended periods for medical or other reasons.
"In one study, horses usually kept outside developed ulcers within a week of being brought into the barn," Williams says. "So make the pasture-to-stall transition as gradually as possible. If possible, bring a pasture buddy in, too, and situate the horses in stalls where they can see, smell, or hear each other."
While some horses thrive on barn life, pasture time is critical to keep their stress quotients low. Ralston reminds owners to resist impulses to "hothouse" their horses and, instead, provide plenty of pasture, the time to enjoy it, and under saddle activities that keep horses' brains busy.
"The least-stressed horses I've even seen are owned by competitive and endurance riders," Ralston says. "They keep their horses outside most of the time, they don't oversupplement them or overfeed grain, and their horses' activities are generally repetitive. They let the horse be a horse."
Finally, Williams warns never to underestimate the effect of human stress on equids. If owners want training, riding, or performance sessions to be productive and tension-free, they must leave their own stress at the barn door.
"We transmit stress from our daily lives to our horses, and they reflect our moods," she says. "So, if you've had a bad day, don't ride. Groom your horse, spend some time with him, but save the ride for a day when you're more relaxed. If you want to manage your horse's stress, start by keeping yourself happy and healthy."
It's nearly impossible to keep horses unstressed all the time. Be conscious of things that stress your horse and work to manage his environment to reduce stress. This is true whether your horse is a top- level performance competitor or a backyard trail horse.
About the Author
Pat Raia is a veteran journalist who enjoys covering equine welfare, industry, and news. In her spare time, she enjoys riding her Tennessee Walking Horse, Sonny.
POLL: University Equine Hospitals