Summer can provide some of the most glorious weather for riding. However, it also can pose a great risk to your horse – and you as well – in the form of hyperthermia and heat stroke. While air temperature is an important factor for developing heat stroke, humidity also plays a role. The University of Minnesota recommends avoiding riding your horse when the combined air temperature and humidity percentage exceed 150. This is a good guideline to have in mind despite it often not being feasible with multiple horses to ride each day in the humid summers of Virginia. Appropriate preparation is imperative, for example, ensuring that all horses ridden in the heat are well hydrated and fit for the work asked of them. Horses can lose gallons of water via sweating in hot weather, so it is essential to make sure that their water intake matches fluid losses during work. It is also a good idea to offer electrolytes during the summer as these are also lost in sweat.
Hyperthermia is an elevation of the horse’s core temperature above normal, which can lead to heat stroke. A horse’s normal body temperature is generally less than 101.5*F; a horse with a temperature above this level is deemed hyperthermic. Horses that have been worked in heat can develop core temperatures up to 105*F and above; it is vital that the horse’s temperature is reduced back towards the normal range quickly or the horse may be at risk for heat stroke. Heat stroke occurs when the brain is exposed to high temperatures for extended periods of time and may manifest as weakness, lethargy, neurologic signs, collapse, or even death.
Hyperthermia is often unavoidable in the summer, so it is important to cool your horse down appropriately so that it does not progress to heat stroke. After you are done riding or if you detect that your horse is distressed, remove all tack and move your horse to a shaded area near a water source or a wash stall with a fan. Muscles generate heat so you do not need to walk your horse to cool them down as this will cause the muscles to continuously generate heat. You may offer your horse cool (not ice-cold water) and allow them to drink only a few liters at a time while they are still hot. Spray your horse with cold water and then remove it with a scraper. Repeat this process until your horse’s temperature starts to come down. By putting a large volume of cold water on the entire neck and wither you get much greater conduction of heat from the dilated capillaries in the skin over a large surface area. You may add ice to the water to make it colder, however, avoid applying ice-cold water to the large muscle groups e.g. back muscles and gluteals except in cases of heat distress. You may also give your horse an isopropyl alcohol bath to help quickly remove surface heat and reduce core temperature. It is important to monitor your horse’s temperature, heart rate, respiratory rate, and gum character/color. If their temperature, heart rate, and respiratory rate stay elevated without decreasing for a prolonged period of time (>15 minutes) or their gums appear sticky or pale, you should involve your veterinarian in cooling your horse as they may be progressing to heat stroke. Your veterinarian has the ability to administer cold fluids to the horse rapidly, which will replace electrolytes and cool the horse through the vascular system.
Riding in the summer can be enjoyable for both you and your horse as long as measures are taken to ensure that everyone involved stays safe. Even if your horse develops hyperthermia, don’t panic: take the actions listed above to cool him or her off and always involve your veterinarian sooner rather than later if you have any concerns!