The time to pull out the thermometer and stethoscope to check your horse's temperature, pulse (heart rate), and respiration (TPR) for the first time is not when he's looking a little puny and you and the veterinarian are on the phone trying to decide whether it's an emergency. Instead, these baseline measurements should be part of a horse's routine care. The reason: normal ranges of basic health parameters vary among horses, so you need to know what is normal for your horse to discern when it's abnormal.
"With the economy the way it is, people don't want the veterinarian to come out to the farm unless he or she has to come out," says Jeremy Campfield, DVM, of Pacific Crest Equine in Exeter, Calif. "But it is difficult to interpret what the owner is seeing over the phone. Even though it is clear to you, 'My horse is lying down; it hasn't been eating,' to me as a veterinarian that can mean a lot of different things.
"Having the TPR can help us determine whether we need to come out right now because this is an emergency, or whether we can schedule an appointment for tomorrow," says Campfield.
Checking the TPR should be part of every owner's basic assessment of their horse's overall physical condition, no matter his state of health. Joe Bertone, DVM, MS, Dipl. ACVIM, professor of equine medicine at Western University of Health Sciences in Pomona, Calif., notes. "You need to collect these data regularly when the horse is happy and healthy, and if you want to know what your horse's 'normal' is, you need to have a record of routine temperatures and heart and respiratory rates."
The temperature range for most healthy adult horses is 99-101ºF, but external factors, such as illness and extreme hot or cold ambient temperatures, can affect that reading. Mares might have a slightly elevated temperature for a few hours when they are ovulating.
"In a horse that appears normal, a low temperature is often just a bad reading (thermometer wasn't left in long enough or inserted far enough in rectum)," says Brian Fitzgerald, DVM, of F9 Equine Clinic in Columbus, Texas. "An elevated temperature is usually more concerning. A horse with a temperature over 102ºF or 102.5ºF warrants a closer look, but even factors like the weather and the horse's activity level can influence the temperature reading."
The pulse of a healthy adult horse at rest should be 28-44 beats/minute, and the respiration rate should be 10-24 breaths/minute. But all of these can change in a flash, veterinarians say.
"Horses were prey animals. Because of that, they evolved mechanisms to escape predators," says Bertone. "Their heart rate can be in the teens at full rest ... can double when you enter the barn, triple when you enter the stall, and quadruple when you touch them with a stethoscope, especially when you're a stranger. Horses begin to sweat in preparation for exercise before body temperature goes up. This is nearly unique to horses in veterinary species."
Excitement level drastically influences measurements, especially heart rate. "The heart rate of a horse in a strange environment or one that is not used to having a stethoscope placed on its chest can jump to 80-100 beats/minute just because of nervousness or anxiety," Fitzgerald says.
"Even if the horse is comfortable with the owner taking its heart rate with a stethoscope, if there is something that spooks the horse, its heart rate might increase rapidly for no apparent reason," he adds. "If you get an abnormally elevated reading, wait a few minutes and try to eliminate any distractions, then take it again."
He adds, "Depending on level of fitness, its working heart rate could have a wide range." A fit horse will return to its resting range faster than an unfit horse, and recovery depends on the type of exercise.
The endurance horse should be below 70 beats per minute within five to 10 minutes after stopping, according to Campfield.
"Because their heart rates are up in the high 100s, (racing) Thoroughbreds are going to take a good 20- to 30-minute cool-out before they are going to return to normal," says Campfield. "And they are much like humans. The more fit they are, the more quickly they are going to recover. It's funny to watch them come off the track. Some look like they are dying and others walk off the track looking around and ready to do it again."
It's important to help your horse cool down after a workout. Researchers performing a study on recovery after exercising divided horses into three groups: one group simply stopped exercising and had no cool-down; a second group cooled down with a slow trot, and the third cooled down with a fast trot. Those cooled down with a fast trot had quicker recoveries. Their temperatures, heart rates, respiratory rates, and blood lactate levels (levels of lactic acid, an indicator of the animal's overall metabolic or acid/base status) decreased faster following the workout than those of the others, according to Fitzgerald.
One way to gauge whether an exercise is too much for your horse is to check his heart rate 10 minutes after you stop the activity, he suggests. "At 10 minutes after you stop, if its heart rate is still 80 to 100 beats per minute, that was probably a pretty challenging workout for that horse. It should be around 60 or less in 10 minutes.
Research shows that as a horse's level of fitness or condition improves, he can do the same work at a lower heart rate.
Fitness is important for horses of all ages, even older horses, vets say, and the TPR for an older exercising horse will not differ much from a younger adult horse. "In terms of TPR, they are no different than another adult horse," says Bertone, who au-thored the book Equine Geriatric Medicine and Surgery.
However, older horses often have lower resting heart rates than their younger counterparts, simply because they might not be as nervous when having their heart rate taken; this has nothing to do with fitness or athletic ability, and everything to do with being comfortable with the surroundings. "An easy theory to explain this is that older horses are more used to life," Bertone says. "In general, if you have a horse older than 18, if it has been handled all its life, it loves its owners and it's just looking for the next bucket of feed, it's more comfortable with human behavior, and it knows there are no mountain lions around the corner. What changes is the brain and how older horses perceive the world around them. They are more comfortable with that world."
But they need a longer warm-up and cool-down period to protect their joints, muscles, tendons, and ligaments. "An older horse is going to have some difficulties because of wear-and-tear injuries," Bertone says. "Bring them along really slowly. You need to spend a lot of time working that horse into a routine."
The optimum working heart rate of a horse is subjective. Fitzgerald explains, "The take-home message for owners if they choose to measure their horses' TPR during and/or after exercise--and it wouldn't be a bad idea--is they need to look at trends with their horse. Just taking his heart rate after a period of exercise one time is not going to give the owner much information. But if it is the same horse and you exercise the same way, and you take the heart rate each time, that might give you some information as to the horse's level of fitness."
Performing the Basics
Owners should have some basic equipment on the farm to assess these parameters, including a stethoscope and an equine thermometer, and they should have a clock or watch with a second hand available.
Campfield suggests owners ask the horse's vet or veterinary technician how to perform these assessments correctly.
Lubricate the tip of the equine thermometer, move the horse's tail out of the way, and insert the thermometer into the rectum while angling it slightly toward the ground. Leave it in for about three minutes for an accurate reading. Some people prefer digital thermometers because of the reduced risk for breakage and escape of mercury vapors and because the time for reading is less. But many vets prefer the accuracy of a glass thermometer, to which some people tie a brightly colored string around the end and clip it to the tail so they don't have to hold it in place, and so it can be found if the horse defecates and it gets dropped in the stall. Remember to clean the thermometer before putting it away.
The best way to get the heart rate is with a stethoscope. On the horse's left side, push the stethoscope right under the triceps, up under the elbow, directly on the ribs.
"If they haven't listened to their horse's chest before, it is kind of a slower lub-dub sound, and I think some people will double count those and end up with a heart rate of 78 when the horse's heart rate is actually 36 or so," Campfield describes. "Ask your veterinarian to show you how to do it."
You also can detect the horse's pulse in a couple of different arteries on the face, with the preferred location being the artery that runs beneath the bony ventral (front) portion of the mandible, just in front of the large masseter muscle. Your vet can help you find the pulse if you're having trouble. Use your forefinger and press against the artery firmly enough that you can feel his pulse. Count the beats you feel for 15 seconds, then multiply the number of beats you counted by four to give you the horse's heart rate.
Determine respiration rate by watching the rise and fall of the chest or the flare of the nostrils. Watch for one minute, counting each breath (one breath includes an inhale and an exhale).
It is also a good idea to listen to the horse's gut sounds to assess gastrointestinal wellness, says Campfield. Place the stethoscope just behind the last rib. In this case, the absence of noise is a sign of worry. "Listening to gut sounds is another overall measure that helps in the big picture. If you don't hear any sounds at all, that might be something seriously abnormal." Once again, be familiar with your horse's "norm" for gut sounds when he's healthy, so that you have a baseline for comparison.
If you look at your horse's gums, they should be a healthy pink color and they should be fairly moist. To detect capillary refill time, press on the gums with an index finger until the spot you're pressing turns white, then remove your finger and count how long it takes the blanched area to become pink again. This should happen in less than three seconds in a normal horse. Again, be familiar with your horse's normal gum color when he's healthy. The capillary refill time indicates the amount/pressure of blood circulating to the body's extremities. Factors that influence perfusion include cardiac output, blood pressure, hydration status, and metabolic status. A quick capillary refill time is desirable; owners should mostly be trying to detect a prolonged capillary refill time (anything more than three seconds), and leave it up to the veterinarian to interpret why it is prolonged. Examples of conditions that could cause prolonged capillary refill time include congestive heart failure and severe dehydration.
There are two ways to check for dehydration, but neither is as accurate as when the vet orders blood tests. Look at the gums; if they are dry, tacky and pale, the horse is probably dehydrated.
You can also assess hydration status using the pinch test. "Pinch a fold of skin over the neck or loose skin above the eye," says Fitzgerald. "You are testing elasticity. As the horse gets dehydrated, its skin will lose elasticity. In a normal, hydrated horse, the skin will go back to normal pretty quickly after you pinch a fold. A dehydrated horse will take longer. It's a pretty subjective measurement, though, and you need to pinch a lot of horses--especially your horse-- before you know what is normal."
A severely dehydrated horse's heart rate is increased and his eyes appear sunken.
Knowing the basic health parameters of your healthy horse is important so that you'll be able to better describe problems if and when they arise. If you have questions about any of these techniques, ask your vet to demonstrate.
About the Author