As the hot days are approaching, ensuring that your horse is receiving the appropriate care for the challenges they are facing is crucial.

The main thing that comes to mind when we are thinking of summer care for our horses is maintaining appropriate hydration. To achieve this, we must look into the basic knowledge of water needs in horses. A standard horse (545 Kg or 1200lb) in a thermoneutral situation will need to consume approximately 6.6 gallons (25L) of water a day (50ml/Kg BW/day, 0.006gal/lb BW/day). This is mostly obtained through drinking, but the type of feed will also affect the water the horse really needs to get through drinking. A horse eating grass will get a good amount of water from the grass itself compared to a horse eating hay. That means that you will not be able to calculate as well the amount of water that your horse is truly consuming when on grass. Very often, horses are not kept alone so it becomes a challenge to determine what water intake each horse has. Different observations can help you evaluate the hydration status of your horse. Here are things you can look at to help you determine if your horse is drinking enough water:

- Moisture of the gums. When you touch the gums of your horse, it should feel wet. If it feels dry and tacky, this is a sign of dehydration.

- Skin fold. On an adult horse if you pinch the skin off the muscle of the neck and let it go, it should go back to its normal position in less than 2 seconds. If the fold remains longer than 2 seconds, this is a sign of dehydration. The elasticity of the skin changes with age so it is not as reliable on an older horse.

- The capillary refill time is another way to look at the hydration. If you press on the gum to chase the blood away and then remove the pressure, it should return to normal color in less than 2 seconds. If the normal color isn’t back in 2 seconds, dehydration might be responsible for that.

- The position of the eyes. When the hydration is inadequate, the eyes will look sunken into the skull. This is a sign of severe dehydration on an adult horse.

- The 1200lb horse will normally urinate about 8-16 liters of urine per day. Similar to humans, a decrease in urination will be noticed when your horse is dehydrated. For horses that are stalled, this can be easily observed and monitored.  It is much more challenging, however for horses that are turned out.

It's helpful to develop habits for monitoring all of these observations so that you are able to establish what is normal for your horse.  We see slight variaitons to all of these from horse to horse.  The better you are able to learn your horses normal ranges, the more quickly you can identify when something is off and get it addressed before it progresses.

In hot and humid conditions, adding daily electrolytes can be a good option to be able to replace the loss of electrolytes in the sweat. Access to a white salt lick is always important but in moments where sweating is important, it might not be sufficient to replace all electrolytes loss. A salt lick contains only sodium and chloride. Sweat is composed of water and the following electrolytes: sodium, chloride, potassium and minimal amount of calcium and magnesium. Choosing an electrolyte supplement without sugar is ideal. Follow the label indications of the product for administration and ensure there is always access to fresh plain water.

Let’s discuss situations that could occur with the coming hot days!

Horses will have to overcome the heat stress that will come with hot and humid days. Horses have different ways to maintain normal body temperature. Thermal radiation, conduction, convection (wind over the skin), and evaporation. These ways of cooling work well in normal temperature but when the weather becomes hot and humid they are a lot less efficient and increase the risk related to the heat stress. When your horse is unable to cool itself, it can overheat and in the worst-case scenario, suffer from a heat stroke.

How do you recognize that your horse is overheating?

• When your horse is overheating, he is unable to maintain his body temperature in its normal range.
• Horses overheating will exhibit the following signs:
  • Rapid shallow breathing
  • Flared nostrils
  • Unpredictable behavior and gait
  • Very high body temperature
  • High heart rate
  • Profuse sweating

If you suspect your horse to be overheating, the following should be performed:

• Provide shade for your horse.
• Cool your horse by bathing with cold water (if ice can be added to the water, this will even be more efficient). Scrapping the water off or continuously pouring cold water on the horse are two ways to cool your horse. Studies are conflicting on which methods obtain best results.
• Place the horse in front of fan to allow convention to do its cooling job.

If the appropriate actions are not taken when a horse is overheating, it can evolve into a heat stroke. A heat stroke occurs when the body temperature rises above a critical temperature, leading to the malfunction of multiple organs. Signs of heat stroke can be observed when the body temperature is above 107F. This is most often observed when exercise is performed under hot and humid conditions. The ability of the horses to cool themselves is extremely decreased in that kind of condition. Dehydration from important sweating and electrolytes imbalance can also increase the risk of heat stroke. Once the body temperature reaches the critical point, the hemostatic mechanisms of thermoregulation fail and decreases even more the ability to cool the body temperature. Affected horses are lethargic with weak and flaccid muscles. Death can occur if nothing is done urgently.

The hot and humid days will also bring to light horses that tend to have difficulty sweating. This is called anhidrosis. This topic has been previously covered, and you can find more information on our website.

References:

- Water for Horses

Sara L. Mastellar, PhD, Equine Faculty, Agricultural Technical Institute (ATI) Elizabeth Share, PhD, Livestock Specialist, Department of Animal Sciences Haley Campbell, MS, Lecturer, ATI

- Equine Internal Medicine

Stephen M. Reed, Warwick M. Bayly, Debra C. Sellon

- Heat stress in horses: a literature review Hyungsuk Kang 1,?, Rebeka R Zsoldos 1, Albert Sole-Guitart 2, Edward Narayan 1, A Judith Cawdell-Smith 1, John B Gaughan 1