Summer care | The British Horse Society

Increase water intake

In hot weather, your horse will increase the amount of water they drink (for a 500kg horse this could be 50-70 litres or four-six buckets per day)¹. If they don’t have access to enough water, it can increase the risk of dehydration. To prevent this, it’s vital that a constant supply of clean, fresh water is available. Exercising your horse in hot weather will further increase the amount of water they need.

Water has a key role in your horse’s digestive system, where it’s continually secreted into and reabsorbed from the gut. Changes in hydration, by not having enough water, can affect the digestive process and how food passes along the gut. This increases the risk of impaction colic which occurs when a firm ball of feed material blocks the intestine.

Soak or steam hay

Soaking or steaming your horse’s hay is a good way to add extra water to their diet, helping to prevent dehydration. Make sure to introduce any changes gradually to reduce the risk of colic.

Soaking

Soak for 6-12 hours in clean, cold water or one hour in warm water²
- Less time is needed to soak when using warm water or during warmer weather to prevent mould and bacteria growth.
Soaking hay will reduce the nutrient content of the hay. A vitamin and mineral supplement or balancer will help make sure the essential nutrients are provided.

Steaming

Increases water intake while maintaining the nutritional content of hay³
Can help reduce mould and bacteria³.

Water sources

Aim to have more than one water source available and where possible, avoid corners of the field to prevent conflict between horses in shared fields
Larger water containers such as a large water bucket or trough may encourage your horse to drink more than a small bucket or automatic drinker⁴
Make sure containers are cleaned regularly to prevent algae and bacteria growth.

Flavouring

Adding a sweet flavouring to a bucket of water, such as apple juice, can help to encourage a reluctant horse to drink⁵. Make sure that your horse still has the option of plain water in case they don’t enjoy the flavoured water – we don’t want to unintentionally add to the risk of causing dehydration.

Use Enrichment

Enrichment creates a greater variety and choice, positively contributing towards a horse’s physical and mental needs.

Shelter

Shelter or shade is recommended in hot weather. If your horse is turned out, a field shelter provides the best protection from the sun and biting insects⁶. The shade provided by trees and hedges may provide a good substitute but remember it will move with the sun, so there may be certain times of the day when shade isn’t accessible to your horse. Natural shelter also may not provide shelter from biting insects. If you use natural shelter, be aware of poisonous trees and hedges which are unsafe for use around horses.

If you can, stabling horses through the hottest parts of the day, providing their stable remains cool and well ventilated, can be a good option to consider. However, inadequately ventilated stables can become uncomfortably hot and stuffy, and may have a negative effect on your horse’s physical and mental health⁷. Make sure you make any changes to your horse’s management gradually to reduce the risk of colic.

Flies

Flies and biting insects are more likely to be a problem for your horse in hot weather. To help reduce your horse’s exposure:

Keep your horse in during the day and out at night
Use thin fly sheets and masks
Apply a fly repellent spray – always follow the manufacturers’ instructions and don’t use on inflamed or broken skin
Remove droppings frequently from the paddock and housing
Where possible, position the muck heap away from where the horse is kept.

Sun protection

Sun cream isn’t just for humans! Horses with pink skin and grey or white hair are most susceptible to burning so sun protection is highly recommended, especially on pink noses.

Watch

Looking after your horse in the sun

Grazing

The hot weather may affect your grazing, as the sun can dry out the grass, effectively turning your grazing into hay. This grass will still provide enough calories for your horse; however, the nutritional value may decrease. A low-calorie balancer or vitamin and mineral supplement may be needed to make sure your horse is getting exactly what they need. A horse grazed on sun-dried grass doesn’t necessarily need additional forage assuming they’re not losing weight. Horses in medium-hard work might need additional calories.

If your horse is kept on a bare paddock, be aware they could consume more soil or sand, increasing the risk of colic. You may need to feed additional forage to help prevent this. Introduce any new forage gradually over a minimum of 10-14 days. 

Assess the level of work your horse is in before giving additional forage, and fat score your horse to help assess whether they need any additional calories. Remember, your horse won’t burn as many calories through the summer, as they naturally would through colder winter months to keep warm.

Be extra careful if you own an overweight horse or a horse with an underlying condition such as Equine Metabolic Syndrome or Cushing’s Disease and rain is forecast. The combination of rain and sun will cause the grass to grow quickly and if you let your horse eat too much, this could increase the risk of laminitis. Be prepared to control grazing if rain is forecast and introduce your horse slowly back to what will be a very different forage compared to what they’ve been eating before the rain. 

Identifying signs of heat-related illness

It’s vital to recognise when your horse might be struggling in the heat, and taking the appropriate action, so you can maintain their health and welfare, especially in very hot or humid conditions. When a horse’s internal body temperature gets too high, serious heat-related conditions can occur.

Dehydration

Dehydration can occur when a horse loses more water (for example lost in sweat, breath, urine and droppings) than it takes in. Signs of dehydration include²:

Dark urine
Reduced urination
Very dry droppings
Reduced amount of droppings
Higher heart rate than normal
Lethargy and/or depression
Dry skin and mouth with thick saliva
Dull eyes
Longer capillary refill time – the time taken for gums to regain their healthy pink colour after pressure has been applied
Gums that are dark in colour – become redder rather than the healthy pink.

The skin pinch test is commonly thought of as a way to test if a horse is dehydrated. This method uses a light pinch to see how quickly the skin returns to normal. However, research has now shown that this isn’t an accurate measure of your horse’s hydration level⁸.

A horse shouldn’t necessarily be considered dehydrated based on the observation of one sign. The more signs that are present, the greater the chance that the horse is dehydrated and the more severe the dehydration is likely to be². If you suspect your horse is suffering from dehydration, consult your vet.

Heat Exhaustion and Heat Stroke

Heat exhaustion is a serious condition and can occur if the horse is exposed/exercised in very hot or humid conditions for long periods and is often also suffering from dehydration. Signs of heat exhaustion may include the signs of dehydration above and potentially:

Fast, shallow breathing (panting).
Nostril flaring.
Increased rectal temperature, that doesn’t, or very slowly, returns to normal after a period of rest. The normal range is between 37.5-38.5°C.
An irregular heartbeat.
Decreased appetite and thirst.
Slow recovery after exercise.
Muscle spasms.
Reduced performance.
Lethargy.
Dark urine/reduced urination.
Dark mucous membranes (gums).
Synchronous Diaphragmatic Flutter (SDF), also known as “Thumps”, is when the horse’s heartbeat and diaphragm synchronise and causes the horse to show hiccup-like contractions, often with a thumping sound.

If your horse is showing signs of heat-related illness, contact your vet immediately, move them into the shade and provide water to encourage them to drink. Start to cool the horse by continuously applying cold water all over their body, without scraping, until help arrives. It may take 10-15 minutes before you start to see an improvement in the horse’s condition.

If not quickly and carefully managed, a horse suffering from heat exhaustion can progress to develop life-threatening heat stroke, although this can sometimes appear suddenly without warning. Horses suffering from heat stroke can be very challenging and dangerous to manage as their behaviour can become aggressive and some signs may appear neurological, for example losing perception of where they are, with no regard for their handler. The horse may also become unsteady on their feet and/or collapse. If not treated quickly and effectively it can cause damage to the kidneys, heart, lungs, brain or muscles, and in some cases can be fatal¹.

References

Nyman, S. et al (2002) Water intake and fluid shifts in horses: effects of hydration status during two exercise tests - PubMed (nih.gov)
Rendle, D et al. (2018) Equine obesity: current perspectives. UK Vet Equine. Vol 2.
Moore-Colyer, M.J., et al (2016). The effect of steaming and soaking on the respirable particle, bacteria, mould, and nutrient content in hay for horses. Journal of Equine Veterinary Science, 39, pp.62-68.
Harris, P.A. and Schott, H.C., (2013). Nutritional management of elite endurance horses. Equine applied and clinical nutrition. Health, welfare and performance. Saunders Elsevier, Edinburgh, UK, pp.272-288.
Christensen, J.W., et al (2022). Shelter use by horses during summer in relation to weather conditions and horsefly (Tabanidae) prevalence. Applied Animal Behaviour Science, 253, p.105676.
Van Diest, T. J., et al (2021). The effect of water flavor on voluntary water intake in hospitalized horses. Journal of Equine Veterinary Science, 98, 103361.
Janczarek, Iwona, et al. (2020)Effect of air temperature and humidity in a stable on basic physiological parameters in horses. ANIMAL SCIENCE AND GENETICS3 55-65.
Pritchard, J. C., et al. (2008): Validity of indicators of dehydration in working horses: A longitudinal study of changes in skin tent duration, mucous membrane dryness and drinking behaviour.Equine veterinary journal6 558-564.

Thanks to Dr Teresa Hollands, Senior Teaching Fellow (Veterinary Nutrition) at the University of Surrey for her assistance with the grazing advice, and Dr James Risk MRCVS for his assistance with the water increase advice.

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Horse care in hot weather