Hosing horse with heat stress down

Know The Signs: Heat Stress in Horses

We are smack bang in the middle of an Australian summer here and to quote the late great Robin Williams  "It's hot. Damn hot! Real hot!

Last week we had 2 days of 38C leading up to one of 46C.
For my US friends 38C is 100F and 46C is 114F! 

As a responsible horse owner you need to know the signs of heat stress in horses so you can keep your equine pal healthy when the scorching summer days hit.

There are several factors that can contribute to heat stress in horses - increased temperature obviously, but humidity, dehydration and direct exposure to sunlight will all increase the risk of heat stress.

Some animals are more susceptible than others also. Aged horses, foals, horses stabled with poor ventilation, unfit and/or overweight horses and horses expected to perform at increase levels are all at greater risk. This is not to say your unworked middle aged paddock ornament is also not at risk.

So let's get straight to it - what do you need to look for?

Signs of Heat Stress

Visual Signs 

The early stage visual signs of heat stress are:

  • Profuse sweating 
  • Your horse is panting and puffing over 20 breaths per minute
  • Dry hot skin
  • Intense lethargy
  • Dehydration

You can easily test for dehydration in your horse. Simply pinch the skin on the neck down near the shoulder and if it holds its shape and remains raised the horse is likely to be dehydrated. Skin should relax back and resume it’s normal position almost instantly once released.

Your horse may have one or more of the above signs. They do not have to have all of these signs to be suffering.

Vital Signs

You should know how to take your horse's vital signs and what his normal resting signs are.

Vital signs in a healthy horse are as follows:

  • Temperature: 37C – 38C
  • Pulse: 38 – 40 beats per minute
  • Respiration Rate: 8 – 15 breaths per minute
  • Capillary refill: within 2 seconds, also check colour of gums
  • Dehydration: skin return within 1 second

Vital signs in a horse with heat stress are:

  • Increased heart rate over 50 beats per minute
  • High rectal temperature over 38C

Additionally if your horse is showing any of the below symptoms you need to call a veterinarian immediately:

  • Breathing difficulty
  • Signs of weakness or collapse
  • Extreme distress
  • Diarrhoea
  • Typing up type symptoms
  • Colic type symptoms
  • No sweating

Horses who have progressed to the above stage are in a lot of trouble and I can’t stress enough that you need vet assistance as soon as possible.

This short video discusses further the signs you need to look for.

If you unfortunately live many hours from a vet (like me some 4 - 5 hours) then you are probably going to have to go it alone, but still ring your vet. They can talk you through options on the phone and greatly increase your chances of saving your horse.

What to do if you suspect your horse has heat stress?

If you suspect your horse has heat stress you need to take the following steps as quickly as possible:

  1. Move the horse into the shade and start hosing down with cool or cold water. Use a spray and keep the water running constantly. Running water is most effective, but if you only have access to buckets then sponging the horse with as much water as you can will help.
    Spray the water continuously over your horses head & neck and inside the back legs.

    Have a second person scraping excess water of the horse right away. Water itself can act as an insulator and trap the heat under the hair. By scraping off the water and reapplying cool water you prevent this from happening.  

    Adding ice to the water is also shown to be beneficial. Don’t sponge ice cold water over the horses large rump muscles rather reserve sponging to areas that have blood vessels closer to the surface eg. along the head & neck and down the back and ribs. 
  2. Add a fan or stand in a breeze (even if warm) this ensures airflow over the cooling water. Do not put a blanket, even if wet with water over your horse. This will prevent air flow and block evaporation.
  3. Provide plenty of cool water for your horse to drink. Provide two buckets one with clean fresh water and one with added electrolytes. Electrolytes will speed up recover but the main thing is to get your horse to drink so if they refuse the electrolyte water then cool fresh water is better than nothing.
  4. Don’t be in a hurry. You need to continue with this for as long as it takes to get the horses body temperature back to normal and may be up to an hour of hosing depending on the horses initial condition.
Cooling horse down with hose spray

Correct Preparation for a day of extreme heat

Prevention is better than cure for all things when it comes to horses, but particularly in regards to heat stress which can be a life threatening condition in some horses.

I know I am constantly checking the weather, as most horse owners do. In the winter time it’s “is it going to rain? Should I rug? What is the temperature dropping too overnight? Is there any wind chill factor?”

And likewise in the summertime. Each night I check the temperatures for the next day so I can be prepared.

Drinking Water

Horses need continuous access to cool clean drinking water, even more so on hot days. You should take note of how much your horse drinks on a daily basis as it is a good indicator of any changes within your horse. Generally on a normal day a 500kg horse will drink anywhere from 20 - 40 litres of water, on hot days this can be as much as 50 - 70 litres of water even without exercise.

Your water trough should be made of a material which is most effective at keeping it cool. Concrete troughs are ideal, but anything apart from metal will do and the larger the better. More water will stay cooler than having a small amount in a small container. 

You need to also consider how the water is getting to your trough or bucket. I know many people here have automatic waterers. In extreme heat the pipes to the waterers also heat up and you are basically delivering lukewarm to hot water to your horse. Obviously again less than ideal.

Horses can be fussy and even when faced with extreme thirst they will often not drink tepid to warm water.

If you are on auto-waterers check out how the water is getting to your horse. Are the pipes buried (good) or laying on the ground (not so good). What are the pipes made of? Metal (not so good) insulated poly pipe (better).

The ultimate test though is on the next warm to hot day simply go and look at your horse’s water trough and put your hand in it.

Would you drink it?

Another great tip is to freeze large ice blocks for your horse. You can put them straight into the horses water to help cool it down, or into a bucket and let your horse lick and crunch away at the ice block. Apples and carrots frozen in there will encourage them to show more interest.

Another way to encourage your horse to drink is to add molasses or a pre-packaged supplement to your horses water. I use Drink Up and both my horses love it and will drink 10 litres of water with Drink Up in it without moving their heads from the bucket.

You need to do this before you have any heat stress issues though, don't use Drink Up or other sweet supplements if your horse already has a problem, at that stage the horse needs electrolytes.

Shade & Air Flow

I speak to many horse owners and they say “even on the hottest of days my horse stands out in the sun even though he has a shady tree or a shelter he could go under”.

That’s OK your horse will decide, but if he does need shade and there is none you are increasing your chances of trouble.

Grey horse in the shade of a tree

Sometimes owners provide three sided shelters in paddock situations and generally these are great for keeping wind and rain out, but they also prevent air flow so your horse may actually be cooler out in the sun than in the shelter you have provided.

Horses kept stabled without any air flow and ventilation are at an increased risk of heat stress than those who are paddocked. I know we think we are doing the right thing by keeping them out of the sun but this is only true if the conditions are suitable.

Use of industrial fans to provide airflow, or water misters can help drop the temperature down in stabled conditions.

Salt & Electrolytes

My horses have 30gm of rock salt in their feed each morning regardless but I increase this to 60gm (approx 2 heaped tablespoons) if I know the day is going to be hot.

Salt encourages your horse to drink during the day preventing dehydration.

At night I add 60gm of electrolyte to their hard feed. If you don’t hard feed then a bucket with chaff will do the trick to hide your salt and electrolytes in.

I have been using Hygain Regain for the past 5 years and recommend it highly. For about 80 cents a dose it really is cheap peace of mind.

If you have a particularly fussy eater, who is likely to sift out the salt/electrolyte mix a small amount of molasses into a big jug of water and damp down the feed. This encourages most horses to eat and will also stick the additions to the feed making it harder to sift through.

quick facts

The amount of heat a horse produces in a 160 km endurance race would be enough to boil approximately 770 litres of water (1)

Horses heat up 10 times faster than humans (2) 

It only takes 17 minutes of moderate intensity exercise in hot, humid weather to raise a horse’s temperature to dangerous levels (2) 

To Ride or Not To Ride?

Not all of us are able to keep our horses in ideal conditions, and sometimes summer can throw us a curveball with some pretty extreme temperatures, but you can do much to prevent heat stress in your horse.  

When contemplating whether you should ride or exercise your horse during the summer there is a great resource called the Horse Heat Index which can be easily used to determine the risks when exercising your horse.

The Horse Heat Index is calculated using Fahrenheit and provide for you below. 

Horse Heat Index

Click on image to enlarge

In Australia both Pony Club Australia and the Equestrian Federation of Australia use the Wet Bulb Globe Temperature system. It’s a little more complicated and you need to have the graph below to work it out.

Wet Bulb Globe Temperature Index Graph

It's easy to use - you simply trace the relative humidity and the temperature and you will get the Wet Bulb Globe Temperature. Example if the relative humidity is 40% and the temperature is 30 the WGBT will be 28. You can then use the infograph below.
Click on image to increase size.

Wet Bulb Globe Temp Infographic Horses and Heat

Click on image to enlarge

Extreme Performance & Competition

If you know you will be competing with your horse in the heat of the day then you need to acclimatise them by trained at similar times and in similar conditions. There is no point exercising your horse in the cool of the morning or evening and then expect them to perform in the hottest parts of the day.

Gentle exposure to increasing temperatures during exercise and teaching your horse to accept the taste of electrolyte water is essential if you are competing in heat. Being able to keep your horse adequately hydrated during exercise and competition is essential to aid recovery and help your horse cope better in the heat.

Extreme performance eg. cross country or endurance must be trained for, do not expect to drag your unfit pony out of the paddock for a whizz around the cross country course, especially not in extreme temperatures.

Keep Your Cool This Summer

Most horses adapt to summer weather if given time to adjust gradually. Use a little common sense, put into place the tips from our blog and you and your horse will have a wonderful summer full of fun.

And keep my horses in your thoughts, I've just checked the weather and it's forecast for 41C AGAIN this Friday!

If you found this article helpful please feel free to share to your social media so more new horse owners know the signs of heat stress in horses and can look after their equine pals this season. As always if you have any questions or need clarification on any aspect of this blog drop us a comment below and we will be more than happy to help you out.

(1) Hygain - Heat Stress in Horses
(2) The Horse Website - Summer Riding  

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Horses are my passion. And while not everything in horses is black and white, and there are many choices you will need to make for your horse, I hope to explain things in a way that helps you make informed decisions, so you can provide the very best life to your horse.