# When is too hot for a horse?



## vikki92 (Dec 18, 2010)

^^Thats a real good question. I live in Florida & it gets super hot, so I also would like to know how hot is to hot?


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## Beauseant (Oct 22, 2010)

There is no general consensus on this as it depends on MANY factors such as:

health/age of the horse
weight of the horse
physcial fitness of the horse
whether there is a breeze or not
humidity levels
availibility of shade or not
color of horse
cloud cover 
even altitude..... 

The good news is that since there is no general consensus, there is no right or wrong answer. Of course, some may try to say it is this or that temperature, but they do a disservice to the horse owner because what is too hot for one horse may not be too hot for another.

Know your horse's comfort level, and consider the area where you live and the current humidity....and go from there.

Here's my personal factors to consider:

Our horses live in a very high altitude, on top of a mountain. That is good news and bad news. Good news is that there is almost always a breeze blowing. Bad news is that because of the high altitude, the suns rays are closer, which equals hotter and an increased risk of skin cancer, especially for our gray OTTB. Hence, we use a fly/grooming spray with sunblock in it. They have no shade in the dry lot, but their grazing pastures do have shade from trees....

Our OTTB has a high baseline body temp, he is always hot/warm to the touch.....high metabolism, I suppose. He is also a dark dark gray, some parts of him are black, so he absorbs the sun's rays more than a light colored horse, which makes him feel like he is baking when you touch his fur on a sunny day. Overheating causes him to gulp his water in large amounts while in pasture, and he has had an episode of colic/severe stomach cramping from this. From observations last year(10 minutes grazing in the sun with no shade on an 86 degree day with high humidity and he was sweating and foamy all over his body)..... he does not do well in the sun/heat. 

Our Belgian is fat and hairy...but she is a light chestnut. Her fur does not absorb heat as much as our OTTB....but her weight and her hair density puts her at risk of overheating and electrolyte issues as she sweats copiously in the sun on hot and high humidity days...... she does not have high metabolism, and her baseline body temp is lower than the OTTB. 

Between the two, the lighter colored, fat hairy Belgian does ONLY slightly better in the heat than the dark colored, normal weight OTTB. Both only do light "work".

Neither do as well in the heat/sun, theoretically, as a normal weight, light colored, physically fit quarterhorse would.

Both our horses have stalls with two dutch doors each, and a well ventilated barn with both ends of the barn walls and one side wall equipped with sliding doors the size of the wall to improve air flow. They also have stall fans and a barn fan. Still, we would like them out in the grazing pasture with the shade trees and mountain breeze whenever possible.....and that will be a day to day decision, based on the wind, temp and humidity.

To generalize: knowing our horses' body conditions(dark, hairy, fat, etc) and the environmental conditions they live in: they would need to come in to their stalls during the hottest part of the day more often than alot of other horses.

HSI(heat sensitivity index) should NOT take the place of knowing your horse's ability to withstand the heat. HSI is a generalization and should not be something you base your decision on. JMO!!


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## PaintHorseMares (Apr 19, 2008)

Here is a good general set of guidelines (assuming a healthy horse)...

A good rule of thumb when assessing how the heat will affect your workout is to measure the Heat Stress Index (HSI). If the sum of the temperature in degrees Fahrenheit plus the percent of humidity totals less than 120, all systems are “go.” If the sum is greater than 150, particularly if humidity contributes to more than half of this number, your horse’s natural cooling mechanisms will be compromised. You should consider lowering the intensity of your workout, shortening the length of time, or riding later in the day. If the HSI is greater than 180, a horse cannot regulate his core body temperature naturally, so he should not be forced to work. For instance, if it is 100 degrees with 80 percent humidity, leave your horse in a shaded paddock with plenty of cool, clean drinking water and go have a cold drink yourself.


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## avjudge (Feb 1, 2011)

Beauseant said:


> There is no general consensus on this as it depends on MANY factors .....


To which list I'd add whether the horse has been in hot temps for a while or if it just got hot (or the horse moved to a hotter climate). There's an army lab that does research (for obvious reasons!) on the effects of hot & cold weather on people and NPR's Science Friday did some features on this a summer or 2 ago - it takes WEEKS for the body to properly acclimate to hot temperatures, to adapt to handle as much heat as it can handle. It's got to be the same for horses (or any warm-blooded animal). 

So a hot day in spring can be more dangerous that a hotter day in late summer. 

I had a dog lose it on the trail once when we had one of those hot May days - staggering & falling until we got to a puddle & he could flop down in it and cool off. It was hot for May (and the leaves aren't out yet so little shade) but no warmer than a normal July day.


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## Indigosblue (May 9, 2011)

I've owned a Belgian/TB/QH cross that would.not.work. when it was hot! Guess he decided for himself when it was too warm for him!


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## eventer757 (Feb 23, 2009)

Indigosblue said:


> I've owned a Belgian/TB/QH cross that would.not.work. when it was hot! Guess he decided for himself when it was too warm for him!


:rofl: Well that took the guess work out of it!


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## Indigosblue (May 9, 2011)

yeah, one rider tried to "force" him to work once..... he just completely ignored the rider... now we've moved to a colder climate, and he's SO much more happy here!! Some horses just can't live in some climates... he was always sick and here he hasn't had one health problem!


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## jdw (Mar 17, 2011)

PaintHorseMares said:


> Here is a good general set of guidelines (assuming a healthy horse)...
> 
> A good rule of thumb when assessing how the heat will affect your workout is to measure the Heat Stress Index (HSI). If the sum of the temperature in degrees Fahrenheit plus the percent of humidity totals less than 120, all systems are “go.” If the sum is greater than 150, particularly if humidity contributes to more than half of this number, your horse’s natural cooling mechanisms will be compromised. You should consider lowering the intensity of your workout, shortening the length of time, or riding later in the day. If the HSI is greater than 180, a horse cannot regulate his core body temperature naturally, so he should not be forced to work. For instance, if it is 100 degrees with 80 percent humidity, leave your horse in a shaded paddock with plenty of cool, clean drinking water and go have a cold drink yourself.


Dont know where you got this, but I intend to try it out. I live in Texas and sometimes I think some of the horse folks around here are crazy to ride horses HARD in the supreme HEAT. If I am totally uncomfortable and reaking wet from sweat, I figure my horse must be feeling it worse than me!! Thanks.


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## Iseul (Mar 8, 2010)

We just go by whether or not the horse is soaked with sweat just from being in the field. If they aren't mostly covered in sweat, they get ridden. I normally don't ride if it's over 85-90 because I'm too uncomfortable; our horses are normally fine with it, but I'm not, haha.
_Posted via Mobile Device_


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## PaintHorseMares (Apr 19, 2008)

jdw said:


> Dont know where you got this, but I intend to try it out. I live in Texas and sometimes I think some of the horse folks around here are crazy to ride horses HARD in the supreme HEAT. If I am totally uncomfortable and reaking wet from sweat, I figure my horse must be feeling it worse than me!! Thanks.


I original saw this HSI formula in an article on a university vet school (don't remember which one) website many years ago, and the 120, 150, 180 numbers were easy to remember. This particular excerpt is from horsechannel.com, I believe.

Here in NC, we have to hot, humid summers. I rarely ride during the heat of the day when it's over 90 degrees because of the humidity, or the mares will literally be dripping sweat from their chin to their butt. It doesn't seem to bother them at all, but it's much more comfortable for me riding very early or late in the day anyway.


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## EquineLover (Jan 24, 2011)

It deoends on the horse, it never gets very hot here so I do't know. Always hose them down afterwards though, and I suppose don't force the horse to work for excessive periods.
_Posted via Mobile Device_


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## candandy49 (Jan 16, 2011)

PaintHorseMares said:


> I original saw this HSI formula in an article on a university vet school (don't remember which one) website many years ago, and the 120, 150, 180 numbers were easy to remember. This particular excerpt is from horsechannel.com, I believe.
> 
> Here in NC, we have to hot, humid summers. I rarely ride during the heat of the day when it's over 90 degrees because of the humidity, or the mares will literally be dripping sweat from their chin to their butt. It doesn't seem to bother them at all, but it's much more comfortable for me riding very early or late in the day anyway.


I also know of the HSI formula and saw it many years ago in a horse magazine, The Western Horseman. The article was written by Robert Miller DVM (now deceased).


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