Dehydration Colic

At this time of year in Australia the southern states are freezing through the cold winter months while the northern states are in the middle of the dry season. Whether it is due to freezing cold water and dry forage or because it is hot and dry and the moisture in the grass is low, horses can easily become susceptible to colic due to dehydration.

 Horses must drink 20-40 litres of fresh water every day and can dehydrate quickly if water is too cold to drink, frozen or unavailable. Horses that aren’t getting enough water are at a greater risk of colic from indigestion or impaction. This article will outline the signs to watch for, treatment and ways to prevent dehydration colic in horses.


Colic is a sign of abdominal pain as oppose to a condition or diagnosis. Depending on the severity of the abdominal pain, all the signs below or only a few may be present.

Visual signs of colic:

  • Pawing or kicking at the ground
  • Looking back towards the flank
  • Restlessness
  • Laying down and getting up repeatedly
  • Rolling
  • Posturing as if to urinate/defecate
  • Stretching
  • Playing with water, but not drinking
  • Reduced appetite
  • Excessive sweating
  • Decreased manure production, and/or dry/hard manure.

Signs on clinical examination may include:

  • Reduced or absent gut sounds
  • Rapid breathing (>20 breathes per min)
  • Increased pulse rate (>48 beats per min)

Signs of dehydration include:

  • Dry and tacky gums
  • Skin tent that takes longer than 2 seconds to flatten
  • Capillary refill time over 2 seconds

What causes dehydration colic?

In winter a frozen water trough is the usual dehydration culprit, but occasionally horses choose to not drink water simply because it is so cold. In the northern states the opposite may be true with horses reluctant to drink hot water or dams evaporate leaving an increasing concentration of unpalatable organic matter in the dam water. In addition, increased sweating- through being exercised in the heat or with a hairy ‘winter coat’, or over rugging will also cause dehydration. Changes in feeding and stress due to inclement weather conditions can also be contributing factors.

The good news is that most cases of dehydration colic can be treated in the field through sedation, pain relief and addressing the hydration issues early.

How is a diagnosis made?

When you call your veterinarian out to a colicky horse they will start by performing a complete physical examination. This will include heart rate, respiratory rate, temperature, gut sounds and hydration status. A rectal examination may also be performed at this point to assess the location and condition of the gut contents. Depending on the severity of the colic your vet may also decide to take a blood sample for analysis, take a ‘belly tap’ sample of peritoneal fluid (the fluid surrounding the intestines) or perform an ultrasound examination of the abdomen.

Treatment for dehydration colic

After a thorough examination your veterinarian will usually pass a stomach tube via the nostril down into the stomach. After ensuring that there is no gastric reflux (fluid in the stomach) they will then use the tube to administer a large volume fluids and electrolytes.

At this stage your horse will usually be treated with sedatives and anti-inflammatories to control the pain. Most horses recover fully following this treatment although it is not completely out of the ordinary for a horse to require this treatment more than once.

Depending on the individual case you will usually be asked to avoid feeding your horse until he has made a full recovery. During this time, you should provide plenty of fresh water and assess for any further signs of discomfort and monitor faecal output.

Occasionally more intensive medical treatment is required, particularly if the horse has failed to respond to standard treatment in the field. This more intensive treatment may include admitting the horse to hospital for continuous intravenous fluid therapy to correct the dehydration, frequent drenches (every few hours) by stomach tube to hydrate the gut and its contents and the administration of medication as required.

For those horses that fail to respond to medical treatment surgical intervention may be required. Fortunately, these cases are few and far between.

Ways to prevent dehydration colic

During winter it is important to keep water buckets and troughs ice-free, so your horses have access to an adequate water supply. Additionally, some horses don’t like to drink extremely cold water, so getting them to drink enough in the winter can pose even more of a challenge. Here are some tips to help horses get enough to drink during winter:

  • Feed moistened feed when possible; add warm water to the horse’s regular feed
  • Consider adding beet pulp soaked in warm water to feed
  • Moisten hay
  • Prevent water sources from freezing
  • Offer additional, warmer water to all horses if possible, particularly older horses and those prone to colic episodes
  • In warm weather offer cooler water and check water temperatures in troughs and top up with cold water as necessary
  • If dams are running dry dilute dam water with rain or town water or provide buckets of clean water. This is particularly important if you notice horses are reluctant to drink, or their water supply is not of the usual quality
  • Ensure horses are ingesting adequate levels of salt; salt makes a horse thirsty, which will encourage him to drink more. Access to a free-choice salt block is ideal. Horses should ingest about 2 ounces of salt per day
  • Consider supplementing your horse’s diet with an electrolyte to encourage drinking

And lastly some general advice to help minimise the chances of colic over the winter period:

  • Increasing the forage in a horse’s diet will help prevent impactions and will also reduce the risk of hypothermia (low body temperature). Horses require more calories in the winter just to stay warm, and the body’s fermentation process for digesting hay and roughage also generates heat that helps maintain body temperature. Grain and sweet feed do not provide the same warming and digestive benefits as a continual forage supply
  • Make any dietary changes gradually and keep to a set routine feeding at the same time daily
  • Ensure your horse has access to shelter in bad weather and shade during the heat
  • Avoid feeding horses off the ground in sandy and dry conditions
  • Annual or biannual dental examinations and floats by your vet are essential to aid digestion and help prevent feed impactions

Regular faecal egg counts and a worming plan should also be developed with the help of your vet