I thought the article was interesting because of the information it presented, and also because I thought it missed a few useful points that I consider "common knowledge" among endurance riders.
Here are some of the high-points of the piece:
Michael Lindinger, PhD, MSc, an animal and exercise physiologist at the University of Guelph, explains: "It only takes 17 minutes of moderate intensity exercise in hot, humid weather to raise a horse's temperature to dangerous levels. That's three to 10 times faster than in humans. Horses feel the heat much worse than we do."
And the effects can be serious. If a horse's body temperature shoots up from the normal 37 to 38°C to 41°C (98.6 - 105.8°F), temperatures within working muscles may be as high as 43°C (109.4°F), a temperature at which proteins in muscle begin to denature (cook). Horses suffering excessive heat stress may experience hypotension, colic, and renal failure.
Scary, right? Reading that bit, I wondered why the pastures in the Midwest aren't full of barbequed horses.
This guy was a researcher who worked on the conditions for the Atlanta summer Olympics, and I know a lot of good information came out of that--and I also don't remember any equine metabolic crashes from that event. Clearly the research found ways for humans to avoid cooking their horses. And, in fact, the article has some good suggestions, including
* supplement electrolytes in working horses
* rinse the horse's body with cool water
* keep the horse in the shade
* acclimate horses to heat by spending 4-5 hours each day for 3 weeks in hot conditions, and get them accustomed to working during the hottest part of the day.
Great advice, but sometimes not practical for people who can't carry a bucket of salty water on the trail with them, who compete in events held on a sunny mountainside, and who don't live in (or near) a hot climate and can't take three weeks off in advance of every competition.
Here are some practical workarounds that I've learned over the years:
Rather than "teaching the horse to drink electrolyte-enhanced water", as the researcher suggests, most endurance riders use a dosing syringe to make sure that their mounts get supplemented electrolytes. I daresay that the much of the "salty area" in the photograph the researcher referred to was not only salt from normal horse sweat, but also salt from the extra electrolytes that endurance horses are commonly given.
The electrolyte supplementation helps to maintain the salt balance of the horse's blood, and also makes the horse feel thirsty so she will drink at puddles and water tanks along the way.
Proper hydration is vital. Here's a quote from an article written by endurance rider and veterinarian Susan Garlinghouse:
As the body dehydrates and blood loses plasma volume and fluidity, the cardiovascular system becomes less efficient at transporting oxygen and other resources throughout the body. The heart rate increases to compensate, so that a horse that canters easily at 130 beats per minute when fully hydrated may have a heart rate of 20-30 beats higher when dehydrated, simply due to the extra work of pumping less fluid blood. Not only does this result in slower recoveries, but it also has a significant effect on the efficiency of muscle function. To maintain the same intensity of work, the horse will rely more and more heavily on anaerobic metabolism, contributing to faster fatigue and greater incidence of metabolic disease, such as colic or tying-up. As effort increases and efficiency decreases, the body responds as though to an emergency (which, in fact, it is), and begins to shunt blood flow away from less-vital organs, such as the gastroin testinal tract, in order to maintain maximum circulation to heart, lungs, muscles and central nervous system. As blood flow decreases to the digestive tract, gut motility slows and may stop entirely, leading to colic until blood flow and motility are restored.
So, a big part of keeping my big horse cool is keeping her hydrated and keeping the blood thinned with water so it's easier for her heart to pump. The heart doesn't work so hard, it doesn't beat so often, and the horse doesn't get so fatigued.
Another useful technique is to keep her wet on the outside, by sponging her at creeks and water tanks and by squirting her with bottles water I carry on my saddle for that express purpose. By putting water on her (and scraping the water off promptly, so that the water doesn't just heat up and act like an insulating blanket!) I can decrease her need to sweat--which means that the water she would normally use to sweat for cooling can stay inside her body.
Because Fiddle is large and dark, I carry up to 5 bottles of water on a hot, dry 20-mile loop, and will only drink two of them. The others (which I refill at water tanks whenever possible) get dumped on her as we move down the trail. If her skin is dry or hot, I dump on water until it isn't, and until the water I scrape off is cool instead of warm.
Another technique for keeping cool is to slow down. A hot humid day is not the time to push my Swampland mare for a fast finish. When the weather is cooler we can speed up a bit. We also trot in the sun and walk in the shade, to maximize the time spent out of the direct sunlight. Sometimes that means we change gaits every 1/2 mile, which is fine. In practice it means that on a hot ride like Renegade Rendezvous we finish 26th out of 33, whereas on a cooler ride like Klickitat Trek, we were able to finish 19th out of 53. The heat makes a huge difference.
Here's something else: build long, lean muscles in the horse, rather than big bulky muscles, because bulky muscles are harder to cool. Even a quarterhorse (or a standardbred) can build the kind of lean muscle that occurs rather naturally in many Arabian horses, but it takes effort and time. I spend a lot of time (years!) in training going slowly--trotting rather than cantering, and cantering rather than sprinting along the trail at full-tilt, so that my big mare's muscles are the long stringy type.
The result is that, although she is still gigantic, she is built more like a marathon-runner rather than like a body-builder.
Here's our vet card from Renegade:At the vet-in, she scored all A's (except capillary refill--that's odd!), and her heartrate was 32. She had travelled about 5 miles on flat, easy trails earlier in the day, and had spent the rest of the afternoon snoozing in the shade.
At the first vetcheck, her scores were A's again, and she pulsed down to 60 beats per minute within 60 seconds of arriving, despite carrying me uphill for 10 miles.
At the final vetcheck, she pulsed down as soon as we crossed the line--I didn't even get my saddle off before Ryan pulsed her in. More important to me was the vet's pulsecount, taken 60 seconds after a CRI trot-out: 48 bpm. In other words, my horse was properly hydrated and not overly tired at the finish line.