Updated: Dec 3, 2020
Summer rugging is all about compromise.
On the plus side a rug helps block heat absorbed by solar radiation, however as there is little to no gap between the rug and the skin heat is still transmitted to the horse, and on the minus side a rug makes a horse’s ability to cool down through evaporating sweat less effective.
What we know from experiments is that horses are uncomfortable in temperatures over 25oC whether they are wearing a rug or not. A study in Australia found horses wearing rugs had a higher temperature and sweated more than unrugged horses, however wearing a rug appeared to reduce irritation caused by flies (tail swishing, pawing etc.).
There are many variables influencing how hot a horse feels and if a summer rug may be appropriate. On a hot summers day a 14hh 6yo grey arab with a bcs of 5 on a fibre based diet with a clipped coat in good health in a paddock with a good tree shelter belt and grass cover under foot is not going to feel the heat as much as a 16.2hh 15yo black warmblood with a bcs of 7 being fed grain, unclipped with EMS in a white sand yard with no shade. Each item can make a few degrees difference adding up to quite a large difference between horses.
We can’t change our horses coat colour, but we can control the length of hair, so if your horse doesn’t have a good short summer coat you can clip them. And if you are going to put a rug on your horse in summer use a white rug. Whereas if you are rugging in winter a darker/black colour would be more efficient as it absorbs more heat.
Reasons you might put a rug on a horse in summer: insufficient shade, protecting the coat from sun bleaching or keeping horse clean before an event, deterring flies, to protect from other horses in herd biting. If you decide to rug, what we know is that
*Cotton is cooler than nylon/ polyester.
*White is cooler than black.
*Wet is cooler than dry (for about an hour)
*Mesh allows more air flow but is less durable.
*Wet polyester mesh doesn't hold as much water as cotton, so dries out (warms up again) quicker than cotton.
So we have to weigh it up and compromise between temperature and strength. Nylon/ polyester is stronger than cotton, but it doesn’t breath, so your horse will sweat more. A flag cotton is very light, but not so durable. Mesh allows more effective evaporation, as a solid rug blocks wind, however mesh can rip more easily. If your horse is easy on rugs perhaps a wet white flag cotton rug. If you have a rug wrecker perhaps a wet white med-heavy weight cotton ripstop with nylon/ polyester mesh panels. A wet rug is heavy, I suggest hosing your horse, putting the dry rug on, then hosing the rug and horse.
Horses are larger than us and covered in hair, this means if you feel hot, your horse feels hotter, so we need to be extra careful riding in summer, riding early in the morning or in the evening and reducing the intensity of exercise. Pre-cooling also works, read my pre-cooling blog from last summer. After exercise cool your horse with cold water all over in the shade, if there is no breeze gentle walking creates air movement to improve evaporation. There is no need to scrape water off, leave it on your horse to evaporate off.
Having your horse a little lighter in summer will help them feel cooler, as the smaller the overall mass and the larger the surface area compared to the mass the more able the horse is to lose heat to the environment. Refer to my blogs about body condition scoring part 1 and part 2.
Diet. Grains and concentrates create more heat as they are digested, so good to warm a horse in winter, but in summer particularly if your horse is having less work can be cut back or removed from the diet. If your horse is a poor doer consider feeding oil in summer as a high energy feed that creates less heat during digestion.
Hydration. Make sure your horse always has adequate water and electorlytes to replace sweat. You can also soak a haynet, this reduces the sugar content of the hay and increases the fluid consumed. Or use a soaked feed like speedibeet to provide fibre and moisture. Plus buckets of molasses water.
Is your horse sweating? If we are exercising them they sweat profusely becoming wet, if they are just relaxed sweating gently the air evaporates the water part of the sweat (this is how sweating is designed to cool the body) so the horse may not feel wet or damp to touch. It also explains why you may find your horse dry but covered in salt crystals on a hot day. If your horse does this first rule out any medical issues. Otherwise this is reported to occur when it is hot, hot, hot. Make sure your horse has plenty of salt to replace what has been lost, and implementing as many cooling strategies as you can may help reduce it. A rug that is pressed fitting tight against the body may cause wet sweat patches as the moisture can’t evaporate efficiently.
Paddock environment. Trying to maintain plant cover reduces the amount of heat that radiates and bounces back off the ground, so carefully managing pasture is important. Bare sand will reflect more heat. Solid shade is obviously going to block more heat than partial shade, but airflow is also important. A shelter with a solid roof and open sides might be better than a solid closed in stable. Allowing about 2metres space between your horses back and a tin roof will decrease heat radiating from the roof being absorbed by your horse. Shade cloth sails and sides can be very useful whilst waiting for trees to grow. An alternative for a paddock lacking shade is to change routine to put horses out in a paddock when cooler over night and in the stable or shaded yard during the hotter part of the day.
Other cooling techniques: sprinkler or hose down arena or yard. Run water across the roof and down shade cloth sides. Set up a mister and or fan in the stables. And hose your horse throughout the day.
So, it is all a compromise based on your individual circumstances. Simplistically it is best to avoid rugging and have your horse in full shade, if that is not possible then a light weight wet cotton rug might be suitable.
Please comment if you have any other tips for keeping horses comfortable during our hot Aussie summer.