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Caring for Horses in Summer

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.


Caring for horses in summerThe risk of dehydration and related problems is much higher during the summer months, particularly for performing horses that are regularly exercised and lose large amounts of body salts and fluid in sweat. 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.

HUMIDIMIX® is an electrolyte supplement that is designed specifically for horses working under Australian summer conditions. It is given at the rate of 2-3 scoops per day for a 500kg horse (45-67g daily). It is best to divide all electrolyte supplements between the morning and evening feeds in order to get a more constant intake of the important body salts.

Rehydration fluids and pastes designed specifically for horses are also available to replace salts and body fluids lost during exercise or travelling. RECHARGE® Liquid is a “sports drink” for horses. It is designed to quickly replace lost body salts without having to wait for the horse to consume a meal. It can be given undiluted over the tongue by dosing syringe or mixed into drinking water. It is ideal for replacing electrolytes after travelling, in between classes at shows or other competitions and prior to travelling home from race meetings or other events.

RECHARGE® will stimulate the thirst response and encourage horses to drink. This is particularly useful when away from home as many horses are reluctant to drink unfamiliar water. It is very important to always provide fresh drinking water after giving a horse any concentrated electrolyte replacer.

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.

The following cool down process is recommended after work in hot conditions:

  • 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.
  • A refreshing wash can be made by adding 4 tablespoons of RAPIGEL - a muscle and joint relieving liniment - to 8 litres of water. Sponge all over the body, particularly on the legs and under the belly. Wait for about a minute and then scrape off.

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. Horses suffering from “anhidrosis” or “dry coat” are particularly susceptible to heat stress as they have difficulty cooling their bodies. Anhidrosis is discussed in more detail below. Severe cases of heat stress can lead to collapse, convulsions and death.

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 such as RECHARGE® Liquid as soon as possible. A daily electrolyte supplement such as HUMIDIMIX® should also be added to the horse’s feed on an ongoing basis.

Anhidrosis (Dry Coat or Non-Sweating Disease)

Anhidrosis, or the inability to sweat to cool the body, is a condition that can develop in horses kept in hot, humid environments. Although it is often seen in racing and other performance horses, anhidrosis can occur in any age, breed or sex of horse. It usually begins in the spring or summer, particularly during early unseasonally humid conditions, when horses have less time to adapt to the change of climate.

The underlying cause of dry coat is not known. Horses moved from cooler climates to tropical areas often develop anhidrosis within 1-3 months, but it can also occur in horses bred and reared under tropical conditions.

Affected horses may sweat heavily initially but over a 1-3 month period, sweating will reduce to limited patches under the mane and between the legs. Once the horse stops sweating freely they will “puff” and blow forcibly for up to 30 minutes after exercise, as they attempt to cool their bodies. The horses coat often becomes dry and may become thin over the head and upper neck. Affected horses have poor stamina and fatigue easily. In severe cases they can develop heat stress and collapse during exercise.

Anhidrosis is a very difficult condition to treat. Full recoveries are rare if the horse remains in a hot, humid climate. Some horses will regain the ability to sweat if they are moved to a cooler climate. This is often not practicable and the following management measures may be of use.

  • Try to get the horse fit before the hotter months of the year.
  • House in a cool environment such as an air conditioned stable, or a high gabled stable with a ceiling fan or ridgetop roof vents; provide shade for paddocked horses.
  • Exercise the horse during the cooler times of the day or evening.
  • Feed an electrolyte supplement designed for horses in hot, humid conditions such as HUMIDIMIX® (1 scoop in the morning and 2 in the evening feed). Feed all year round if the horse is being exercised. Supplement with 1000-5000 IU of Vitamin E (eg. WHITE-E® powder or liquid) daily.
  • Provide extra attention to cooling the horse down after work with cold hosing, scraping and walking as described above.
  • Feed low roughage, extruded or fat-supplemented diet to help reduce the heat produced during fermentation of fibrous foods in the large intestine.

Insect bites

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.

Insect bite dermatitis is a very common cause of skin disease in horses. Mosquitoes, gnats, biting midges, sandflies, horse flies, stable flies, wasps and bees can all bite or sting horses. The bites or stings of these insects can cause a wound large enough to ooze serum and can predispose the horse to a secondary bacterial infection. Some insects can cause painful wheals or nodules in the skin that can be very irritating to the horse. Insects such as bot flies, bees and wasps can also frighten the horse and lead to injuries when galloping off in fright.

In regions with high insect numbers light body and neck rugs and fly hoods can be used to help protect the horse from insects. An insecticidal spray such as FLYAWAY® can be used on the horse itself to provide sustained protection, and in stables and areas where insects settle to help to reduce the number of insects in the horse’s environment.

Bites and stings on the head and neck can occasionally interfere with breathing, vision or eating. In these cases contact your vet immediately.

If the skin is broken and there is an open wound apply an antiseptic cream such as SEPTICIDE® (which also contains a fly repellent).

Queensland Itch (Summer Itch, Sweet Itch) - some horses develop an allergic reaction to insect bites, particularly sandfly and midge 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. They often also lose body condition as they spend so much time itching and rubbing.

Severe cases of Queensland Itch should be treated by your vet who may prescribe anti-inflammatory drugs and/or antibiotics. Soothing skin preparations such as SEPTICIDE Cream are also available to help control itching and aid in the healing of the sores.

As Queensland Itch is very difficult to treat it is best to attempt to prevent the disorder in susceptible horses. Sandflies are seasonally active from December to May. Susceptible horses are most at risk in the late afternoon and dusk, and in the early morning when the flies swarm to feed.

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 such as FLYAWAY® Insecticidal Spray are very helpful if applied each day prior to the insect attack time. Heavy applications of FLYAWAY® can provide insect repellent effects for up to one week, however in very sensitive horses daily application is recommended. FLYAWAY® can also be used to treat stables and horse yards. Try to reduce the breeding areas for flies around your stables by cleaning manure away regularly and placing manure heaps away from stable areas. Manure heaps can also be sprayed with an insecticide such as FLYAWAY®.

Summer sores are skin lesions that develop in open wounds, or around the conjunctiva of the eye, or on the lining of the sheath or on the tip of the penis. These sores are caused by the larvae of a worm known as Habronema, which are deposited in wounds and moist areas by flies. The worm larvae cause hard nodules of red brown tissue, which enlarge and spread. The nodules can bleed, ulcerate and weep yellowish to clear tissue fluid. This attracts more flies and if they are also carrying Habronema larvae the size of the lesion and degree of irritation worsens.

Larvae in summer sore lesions and adult Habronema worms which live in the horse’s stomach lining can be controlled by worming products such as EQUIMAX® /EQUIMAX® LV or EQUIMAX® ELEVATION or ERAQUELL worming pellets. The worming products should be administered every 6-8 weeks during the high risk period.

Control of flies on fresh wounds is important to avoid the wounds becoming infected with Habronema larvae. Keep wounds clean and dry to promote healing and make them less attractive to flies. Apply an antiseptic wound product, which contains a fly repellent, such as SEPTICIDE® Antiseptic Cream or CETRIGEN® Spray to healing wounds during the summer months. If lesions do appear consult your vet for advice.

Coat and hoof care

Hot weather and regular sweating can lead to a dull, dried-out coat during the summer months. A daily dose of FERAMO® EVERY HORSE added to the feed daily will help to maintain general health and coat condition during the summer months. FERAMO® range contains vitamin A, iron, copper and cobalt, which are important nutrients for skin health and will help to maintain and darken the coat colour, which often fades during the summer months. Light rugs and hoods will also 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.

The daily addition of about 60mL (3 tablespoons) of sunflower, safflower or blended polyunsaturated cooking oil to the feed may help to improve coat condition. Alternatively add 1-2 cups of sunflower seeds to the ration.

Inspect the hooves regularly for signs of drying out. If the horse has very dry hooves, which commonly occurs when horses are worked regularly on sand tracks or arenas, wash and dampen the hoof wall and sole with water (when hosing down after work) and then apply a moisturising hoof dressing.

For horses with brittle, shelly or “broken away” hooves add a combined calcium and biotin supplement such as CAL-PLUS with BIOTIN to the feed each day. This will help to harden and strengthen the hoof wall and the junction between the hoof wall and the sole. Biotin supplements take time to work as healthy new hoof grows down very slowly from the coronary band. It can take at least 6-12 months for healthy hoof horn to reach the ground surface and the biotin supplement must be continued daily during this time.

Dampen all feed, particularly the evening feed to increase the fluid intake during hot weather. Horses must have access to fresh, clean, cool drinking water at all times. Locate feeders and water buckets and troughs in a shady place.


Horses should be wormed every 6-8 weeks throughout the year. During the summer months use a product that also controls bot larvae such as EQUIMAX® /EQUIMAX® LV or ERAQUELL® pellets. Adult bot flies lay eggs on the legs and belly and can cause horses to panic leading to injuries. Young horses should be wormed with EQUIMAX® ELEVATION Oral Paste for Horses from six weeks of age until they are two years old.

Hot dry spells are a good time to rest horse paddocks to reduce the number of worm eggs and larvae surviving on heavily infected pastures. High temperatures and dryness are fatal to most worm eggs and larvae and 2-3 weeks of spelling during this time will dramatically reduce the level of pasture contamination.


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