You can lead a horse to water ...

Dehydration in horses is commonly an issue associated with warmer summer months. However, due to the changes in routine and conditions, dehydration in winter can be a cause for concern. This article looks at what management changes you can make to help your horse stay hydrated.

Questioning your life-choices is all part of the ‘fun’ of owning a half-ton of prey animal!

A recent review of 58 qualifying studies identified 22 risk factors for colic. The most evidence pointed towards controllable risks, associated with management changes [1] – and there can be no greater set of management changes for a horse than those winter can enforce.

Questioning your life-choices is all part of the ‘fun’ of owning a half-ton of prey animal, at the best of times. In winter, avoiding knee-deep mud and mucking out twice a day in the dark, with a failing head-torch, seem par for the course. But it can get worse. Winter is when a dope-on-a-rope gelding aspires to join the Spanish Riding School at 6am on the way to the lunge pen. One abrupt, uncoordinated capriole and you wake up face-down on concrete. Forget paramedics, the police should probably hear first about the explosion of hair and hooves last seen galloping towards the motorway.

But now consider the horse; locked in the equivalent of a featureless en-suite bathroom for 23-or-more hours a day, denied social contact, fresh food and fresh air. Is it any wonder they move ‘expressively’ the second they leave the box? Failure to meet basic needs (Friends, Forage, Freedom) cause chronic stress, ie. prolonged circulation of ‘fight or flight’ hormones. Stress is associated with stomach ulcers in the glandular region (EGGD) [2], and stress makes the horse susceptible to infection and poor fertility. Eventually, the body has to attempt to re-balance and counter stress hormones by making the horse unresponsive and ‘dull’, or perform stereotypy eg. crib-biting or other such meaningless, harmful behaviour.

Maybe you already realise that changes to feed, carer, exercise, pasture and housing are risks for colic… but what about water? [1]. Water makes the shortlist of risks, but dehydration is something we associate with summer usually.

Water Balance

A horse gets most of the water they need through drinking. Other sources of water include feed and digestion, and as a product of metabolism. Losses are from faeces, evaporation, urine and milk from nursing mares. The body has a water reservoir in and around tissues, organs, blood and the gastrointestinal tract (GIT). The GIT is an especially useful water reservoir for improved endurance during exercise, and for recovery. Water balance is achieved when total intake matches total losses, but it’s never a static situation.

For example, a 500kg horse will drink around 30 litres of liquid water a day, when idle. He can be considered ‘mildly dehydrated’ if he loses about 17 litres (17kg) of un-replenished water. ‘Severe dehydration’ is double this (around 35 litres) and a loss of 95 litres of water can be fatal. He normally loses 25 litres of water a day in faeces, but diarrhoea can increase this to more than 60 litres per day. Then, his body will try to compensate by limiting urine losses and triggering him to drink more.

Drinking Water

Horses normally drink for only 10 minutes a day or fewer. The way drinking water is offered to horses seems to significantly influence the volume they drink in that time. Buckets are preferred to either pressure-valve ‘auto-drinkers’ or float-valve ‘troughs’. Auto-drinkers were used for the same amount of time as buckets by the horses, but less water was consumed.

Buckets also make it easier to monitor water intake but, as concrete is endothermic, a stable floor can chill it further. Insulating the stable floor will not only help the horse stay warm in winter. Larger trugs (eg 40 litres) are perhaps less prone to tipping over, or freezing. Provide two, still, in case one is soiled. As they are heavy, the author has had some success using wooden platforms with heavy-duty castor wheels– the type used to move large plant pots or furniture.

It’s worth remembering that water is a very efficient pH buffer. Since stabled horses are prone to gastric ulcers, this buffering effect may be why horses like to drink immediately after eating a meal, and why they will limit their food intake if drinking water is inaccessible.

Even with good dental health, icy water discourages drinking in cold (less than 5oC) weather [3]. What temperature do horses prefer? Around 20oC! Steamed hay contains twice as much water as dry hay [4] but will be much warmer and likely to be more palatable than icy hay.

Water from feed

A horse at pasture normally takes between 2 and 5 short drinking bouts per day. In the stable, this increases up to 8 bouts – irrespective of watering system. There are several reasons for this including restricted feed, but also that fresh grass is about 80% water! Bagged feeds and dry hay contain around 13% water, or less. So, a stabled horse will need to drink a lot more, to compensate. Some horses learn to dip hay in their water bucket – which then discourages drinking. Steaming restores some of the moisture, and possibly reduces the horse’s urge to dip hay.  

Thoroughbreds fed a diet containing only 50% hay, drank significantly less water and – critically for colic risk – defecated drier faeces, less frequently, than when given a diet including more hay (65%). It is thought that replacing a fibrous hay with grain in the daily ration reduces gut fill. Reduced gut fill then reduces water intake.

To counter this, replace grain with a fibrous feed requiring rehydration / soaking, such as sugar beet pulp. It can be rehydrated to contain the same amount of water as fresh grass. Warm water speeds up the rehydration process and likely encourages the horse to eat in winter. The author would use hot water from the kitchen tap at home (combi-boiler) to rehydrate dry pulp on the way to the yard, to save time and effort.

Water from digestion

Food not only contains liquid water, it also creates it. Water is a by-product of digestion. Here again, long-stem hay wins in the winter hydration stakes!

When horses were fed a hay-only diet, more than three-quarters (77%) of the water in the GIT was found in the large colon (hind gut), compared with only two-thirds (65%) water when fed a ‘complete’ feed including grain. The amount of water in the colon is important because there are several narrowings, or ‘flexures’, where impaction / blockages could occur – resulting in colic.

The difference in water is possibly explained by the higher fibre in hay (digested in the hindgut) and higher starch and simple carbohydrates in complete feeds (digested in the foregut).

In conclusion: What to do to keep your horse hydrated in winter

• Feed as much long-stem hay as possible 

• Substitute grain with rehydrated fibrous feed, such as sugar beet pulp

• Offer ad-lib warm water (ideally 20oC) from two containers, in case of soiling or spillage

• Put a fresh warm bucket of water in the stable - even if there are auto-drinkers 

• Insulate water containers to prevent freezing – especially from cold surfaces like concrete

• Help a reluctant drinker to feel comfortably warm in freezing weather, but don’t over-rug.

Finally, behaviour indicative of stress is not ‘normal’ during any season.

How can Haygain help?

Haygain is committed to improving equine health through research and innovation in the respiratory and digestive health issues. Developed by riders, for riders, we understand the importance of clean forage in maintaining the overall well-being of the horse. Our hay steamers are recommended by many of the world’s leading riders, trainers and equine veterinarians.     

Key resource
Geor, R. J., Coenen, M., & Harris, P. (2013). Equine applied and clinical nutrition E-book: Health, welfare and performance, Chapter 4, Water. Elsevier Health Sciences. 
References:
[1] Curtis, L., Burford, J. H., England, G. C. W., & Freeman, S. L. (2019). Risk factors for acute abdominal pain (colic) in the adult horse: A scoping review of risk factors, and a systematic review of the effect of management-related changes. PLoS ONE, 14(7), e0219307.
[2] Scheidegger, M. D., Gerber, V., Bruckmaier, R. M., van der Kolk, J. H., Burger, D., & Ramseyer, A. (2017). Increased adrenocortical response to adrenocorticotropic hormone (ACTH) in sport horses with equine glandular gastric disease (EGGD). The Veterinary Journal, 228, 7-12.
[3] Kristula, M. A., & McDonnell, S. M. (1994). Drinking water temperature affects consumption of water during cold weather in ponies. Applied Animal Behaviour Science, 41(3-4), 155-160.
[4] Moore-Colyer, M. J. S., Lumbis, K., Longland, A., & Harris, P. (2014). The effect of five different wetting treatments on the nutrient content and microbial concentration in hay for horses. PLoS One, 9(11), e114079.