This weekend I was washing a horse, and after finishing was told to *scrape off the water.
I axed, “Why?” (To me, in the 90º+ day, some moisture would have felt good.)
I was told that “Their hair retains the water, and that can cause them to overheat.”
OK, sorta like the wet-suit principle, I suppose. But it seems to me unlike a wet suit, this moisture evaporates.
So I guess the question is “Is there really a danger of a wet horse overheating as the result of the wet hair trapping body heat?” It seems strange if true. And if not, I didn’t have a credible argument handy for refuting it.
*The doohickey for doing this is a strigil-type device called a “sweat scrape.”
Hmm. Can’t imagine why… Wouldn’t it be similar to people sweatting? You know, the evaporation of water would cool the body? Ofcourse, this is assuming that the horse would be outside, where some wind would help facilitate the evaporation process. Perhaps it wouldn’t work so well inside the horse’s stall?
Now that I think about it, perhaps water doesn’t evaporate off a horse (what with the hair and all) as well as it does off a person?
I’ve always used the sweat-scrape, mostly on account of That’s The Way It’s Done, and, Being Covered With Wet Hair Can’t Be Fun. Kudos to you for asking why.
The evaporation rate of water depends on the temperature of the water - the warmer the water, the faster it evaporates. But what matters here is the tempreature of the surface of the water. If there is a layer of liquid water on your skin, the surface of that layer gets cool, and evaporation rate goes down. But if you wipe off the water layer, the sweat evaporates straight off the 100-degree surface of your skin (or the sweat glands).
Of course convection within the water layer decreases this effect, but I’d guess that the hair and irregularities of the skin prevent efficient convection.
When I used to be fortunate enough to be around horses, I was told that the sweat would cause the horse to cool too quickly. After a horse exercises strenuously, he must be cooled down: you never just put him right back in his stall, and you never allow him to drink a few gallons of cold water when he’s hot.
You walk him until he’s dry; often with a blanket over him so he doesn’t cool too quickly. (If the purpose of wiping off the sweat was to prevent overheating, it wouldn’t make sense to put a blanket on him, right?) Only then can you let him rest and drink his water. Otherwise, he’s liable to get colic, which is unbelievably painful for the horse and possibly fatal.
Ah, Mjollnir, I hereby pooh-pooh this thing you have been told. The purpose of scraping off the excess water after a summertime bath [see below] is so the horse can dry sooner, so you can put him away sooner, so you can get on with your life sooner.
Here’s two websites on “horses overheating.” No mention anywhere about “scrape off the excess water so he doesn’t overheat”, but rather “scrape off the excess water so he can dry sooner and doesn’t catch a chill.” Being very wet doesn’t cause a horse to overheat. Think about it in terms of thermodynamics–evaporation of water always causes heat loss, not heat gain.
Has anyone ever said “don’t let long-haired dogs stand around soaking wet because the excess water will make them overheat”? I don’t think so.
However, I do know the source of the factoid.
Following the train of thought here? The horse gets very wet, he gets sick, therefore, make sure your horse doesn’t stand around very wet, therefore scrape off all the excess water. The problem is in defining what constitutes “excess water”. When it’s 90 degrees in the shade, it doesn’t hurt a horse to be soaking wet. I mean, think about it–all those millions of years evolving out in Kansas and Nebraska, when it’s 90 degrees in the shade for 5 months of the year, and when the heavens frequently open and deluge the unsuspecting prairie with quasi-tropical downpours–what, natural selection weeded out all the horses who couldn’t survive being soaking wet?
…and if it were true that a soaking wet horse will overheat, then in the winter if your horse was cold, instead of giving him a blanket, you’d run the hose over him.
