During the hot summer months in Australia horses are under extra stress from heat, humidity, poor feed quality and insect worry. Some horses tolerate the heat well, while others lose coat and body condition and don’t perform at their best.
About 75-80% of the energy used by the horse’s body is given off as heat. Even during gentle exercise, heat production by the horse is 10-20 times greater than at rest. During fast work, heat production can increase 40-60 times. Horses lose heat mainly by evaporation of sweat and by evaporative cooling from the respiratory tract. As humidity increases evaporative cooling reduces so great care must be taken to avoid heat stress in horses working in hot, humid weather.
Exercising horses can lose up to 10-15 litres of sweat per hour. As well as fluid loss, sweating also depletes sodium, potassium, chloride, calcium and magnesium salts from the body. Horses that are only ridden occasionally should be able to replace their body salt losses from pasture and a salt “lick” in their paddock. However, horses which are exercised and sweat freely on a regular basis should receive a daily electrolyte supplement in their feed.
Cooling down after work
As well as sweat loss during work, horses can continue to sweat for long periods after work, if they are not adequately cooled down.
Be sure to:
• Remove all gear, including work bandages and boots as soon as possible.
• Sponge or hose the horse down with cool water over the neck, body, limbs and under the belly.
• After hosing scrape the horse off immediately. If not scraped off, the water in the coat will retain heat and can actually slow down the cooling process. If the horse is panting or blowing it is a good idea to walk it for a few minutes and then repeat the hosing and scraping.
You should not give very hot horses free access to cold water. It is best to let them drink about 2-4 litres of water initially, then after 10-15 minutes of cooling down let them have free access to drinking water. Horses can be allowed to drink their fill during exercise e.g. endurance or trail riding horses if they continue to work afterwards.
Heat exhaustion or stress
Horses that are worked hard during hot weather, particularly if the humidity is high, can suffer from heat stress. Horses that are unconditioned, overweight or dehydrated are most susceptible.
Signs of heat stress include muscle weakness, rapid breathing and panting, an elevated heart rate and depression. The horse may sweat heavily, however if it is dehydrated it may be unable to sweat adequately to cool itself.
Heat stress is an emergency and immediate steps must be taken to reduce the internal body temperature of the horse.
• The horse should be unsaddled and led to a shady spot.
• If water is not available fan the horse with a shirt or saddle cloth for 1-2 minutes.
• Then walk the horse slowly for 1-2 minutes before repeating the fanning and walking cycle until the horse brightens up.
• If water is available sponge or hose the horse all over and scrape-off within 30 seconds as described above.
• Fan or walk the horse for 2-3 minutes and then repeat the sponging or hosing and scraping. Repeat until the horse improves.
• Let the horse drink 2-4 litres of water at a time and provide an electrolyte replacer. A daily electrolyte supplement should also be added to the horse’s feed on an ongoing basis.
Insects which can worry and bite horses abound during the warmer months, particularly in the humid, coastal regions of Australia. Insects can lead to ongoing annoyance, weight loss, and localised or wide spread skin disease.
Queensland Itch (Summer Itch, Sweet Itch) – some horses develop an allergic reaction to insect bites. Instead of simply suffering from individual insect bites these horses become intensely itchy, particularly along their withers, mane, tail butt, ears and backline. They rub excessively on posts, trees and railings, traumatising the skin, leading to open sores that can become infected and loss of hair. Severe cases of Queensland Itch should be treated by your vet who may prescribe anti-inflammatory drugs and/or antibiotics.
Horses can be partially protected from insect bites by the use of light rugs and hoods, particularly between 4 a.m. and 8 a.m. when insects are most active. If possible, stable susceptible horses in an insect proof environment during these times. Insect repellents are very helpful if applied each day prior to the insect attack time. Try to reduce the breeding areas for flies around your stables by cleaning manure away regularly and placing manure heaps away from stable areas.
Hot weather and regular sweating can lead to a dull, dried-out coat during the summer months. Light rugs and hoods will protect the coat from bleaching, but care should be taken to avoid heavy rugs or materials that cause sweating as prolonged sweat loss under rugs can lead to electrolyte losses and dehydration.
Extract of article “Caring for Horses in Summer” originally published by Virbac Australia. Reprinted with permission.