Horse Care

Why does your horse suddenly have diarrhoea?

Diarrhoea (from Ancient Greek diárrhoia, “through-flowing”) in horses is concerning, often indicating an underlying issue that requires attention.

Diarrhoea in horses refers to the condition where the faeces are more watery, loose, or frequent than the horse’s normal bowel movement.

It’s a common gastrointestinal upset that can be caused by various factors, including dietary changes, infections, stress, parasites, and certain diseases.

Diarrhoea can vary in severity, ranging from mild, transient episodes to more persistent and severe cases that may require immediate veterinary attention.

For horses, diarrhoea can manifest as a disruption in the normal functioning of the gastrointestinal tract, leading to an imbalance in the absorption of nutrients and water.

This disruption can result in the passage of loose, unformed faeces, often accompanied by other symptoms such as dehydration, lethargy, loss of appetite, and discomfort.

Diarrhoea can be a symptom of an underlying health issue, making it crucial for you to monitor your animals closely and seek veterinary advice if you observe any changes in your horse’s faecal consistency or behaviour.

Acute vs. chronic diarrhoea.

Acute and chronic diarrhoea are two distinct types of gastrointestinal conditions that differ in their duration and underlying causes.

Understanding the differences between these types of diarrhoea is crucial for determining appropriate treatment strategies.

  1. Acute diarrhea: Acute diarrhoea refers to a sudden onset of loose or watery stools that lasts for a short period, typically less than two weeks. It is often caused by infections, dietary changes, stress, or reactions to medications. Acute diarrhoea can be a self-limiting condition, resolving on its own without specific treatment. However, it is important to monitor hydration levels in cases of acute diarrhoea to prevent dehydration. If the symptoms persist for more than one or two days or worsen, it is advisable to consult a veterinarian for a proper diagnosis and management plan.
  2. Chronic diarrhea: Chronic diarrhoea, on the other hand, is characterised by persistent or recurrent loose stools that last for an extended period, usually up to four weeks. It can be indicative of an underlying health issue, such as inflammatory bowel disease, parasitic infections, food sensitivities, or metabolic disorders. Chronic diarrhoea often requires a thorough diagnostic evaluation, including faecal examinations, blood tests, and, in some cases, imaging studies to identify the root cause. Treatment for chronic diarrhoea typically involves addressing the underlying condition while also managing the symptoms to improve the horse’s overall well-being. Also, diarrhoea does not have to be present daily for four weeks to be considered chronic. It may come and go over the four (plus) weeks.

Differentiating between acute and chronic diarrhoea is essential in determining the appropriate course of action for addressing the gastrointestinal issue in horses.

While acute diarrhoea may be managed with supportive care and minimal intervention, chronic diarrhoea necessitates a more comprehensive approach, focusing on the specific cause of the prolonged gastrointestinal disturbance.

What can you give your horse for diarrhoea?

When a horse is experiencing diarrhoea, it’s crucial to consult a veterinarian for a comprehensive diagnosis and appropriate treatment plan.

While some mild cases of diarrhoea may resolve on their own, it’s essential to ensure your horse remains well-hydrated during this time.

Electrolyte solutions, such as oral rehydration salts specifically formulated for horses, can help replenish the lost fluids and maintain the electrolyte balance.

Probiotics are also known to aid in restoring the gut’s healthy microbial balance, potentially alleviating diarrhoea symptoms.

Consult a vet before administering any medication or supplements to your horse.

Several factors can contribute to sudden diarrhoea in horses.

Abrupt changes in diet, such as introducing new types of forage or concentrates, can upset the digestive system, leading to loose stools.

Stress, whether caused by transportation, environmental changes, or intense training, can also disrupt the horse’s gastrointestinal equilibrium, resulting in diarrhoea.

Parasitic infections, bacterial imbalances, or viral infections can also be underlying reasons for sudden onset diarrhoea in horses.

Can too much grain cause diarrhoea in horses?

Yes, overfeeding grains can disrupt the delicate balance of the horse’s digestive system, potentially leading to diarrhoea.

Horses are herbivores with a complex digestive system designed for processing high-fibre diets.

Rapid changes in diet or excessive consumption of grain can overwhelm the digestive tract, leading to fermentation imbalances and subsequent diarrhoea.

Ensuring a balanced diet with appropriate forage and gradually introducing any dietary changes can help prevent gastrointestinal upsets.

Consequences of diarrhoea in horses.

Some of the common consequences of diarrhoea in horses include:

  1. Dehydration: Diarrhoea can result in excessive fluid loss, leading to dehydration. Dehydration can further exacerbate other health issues and lead to electrolyte imbalances, weakness, and reduced organ function.
  2. Electrolyte imbalance: Prolonged or severe diarrhoea can disrupt the balance of electrolytes in the horse’s body, affecting crucial functions such as muscle contractions, nerve function, and hydration. Imbalances in electrolytes, such as sodium, potassium, and chloride, can have significant adverse effects on the horse’s overall health and performance.
  3. Nutritional deficiencies: Chronic diarrhoea can impede the proper absorption of nutrients from the digestive tract, leading to deficiencies in essential vitamins, minerals, and other nutrients. Prolonged nutrient deficiencies can weaken the horse’s immune system, compromise its overall health, and impact its performance and vitality.
  4. Weight loss and muscle wasting: Persistent diarrhoea can lead to weight loss and muscle wasting, as the horse’s body struggles to maintain proper nutrition and energy balance. Significant weight loss and muscle atrophy can severely affect the horse’s strength, stamina, and overall athletic performance.
  5. Compromised immune function: Diarrhoea can compromise the horse’s immune system, making it more susceptible to secondary infections and illnesses. A weakened immune system can prolong the recovery process and lead to additional health complications.
  6. Digestive upset and discomfort: Diarrhoea can cause abdominal discomfort and digestive upset in horses, leading to decreased appetite, lethargy, and behavioural changes. Persistent discomfort can affect the horse’s mood and behaviour, impacting its overall quality of life and performance.

Managing and treating diarrhoea promptly, along with addressing its underlying causes, is crucial to prevent these potential consequences.

Timely veterinary intervention, appropriate fluid and electrolyte therapy, dietary adjustments, and supportive care are essential in minimising the risks and complications associated with diarrhoea, ensuring your horse’s swift recovery and long-term well-being.

27 possible reasons your horse has diarrhoea.

An imbalanced diet is one of the biggest causes of diarrhoea.

Certain feeding practices and feeds can cause dysbiosis of the hindgut, which results in a shift in the hindgut microbiota.

Quick or sudden changes to your horse’s diet can shock the microbiome, causing imbalances in the microbial populations which affects nutrient digestion.

Diarrhoea caused by poor dietary management is often treated with changes to your horse’s feeding plan and rarely requires medications.

During bouts of diarrhoea, it’s critical to ensure adequate hydration and to maintain electrolyte balance.

1) Over- or under-feeding

Horses that are eating too much may be putting excess strain on their gastrointestinal system or surpassing the capacity of the small intestine to digest starch.

Underfed horses have nutrient deficiencies that impair gut health and interfere with cell turnover in the intestinal lining.

2) Nutrient imbalances

Imbalances of electrolytes such as magnesium, potassium, sodium, and chloride can result in diarrhoea.

Excess magnesium, particularly in the form of magnesium sulfate can cause diarrhoea. That is why it’s commonly used as a laxative to draw water into the intestinal lumen and increase the rate of passage.

3) Forage type

Some forages are known to increase the risk of gut problems.

High-quality fresh grass or grass hays are best for horses recovering from serious gastrointestinal issues.

Hay that is less fibrous and easily digestible will cause less irritation through the digestive tract. This typically means second-cut grass hays are preferable over first-cut hay

High-quality alfalfa hay can be used to promote food intake in horses with low appetites, but alfalfa hay should not represent more than 10-20% of your horse’s forage intake.

4) Poor grass/hay/forage quality

Inconsistent hay quality can be a major cause of diarrhoea episodes for horses.

The hay you have available to buy changes depending on the time of harvest, soil conditions, and hay maturity.

All of these factors alter the nutrient composition and water holding capacity of the forage.

Ensuring consistent hay quality can prevent diarrhoea episodes.

Change hay gradually to allow the microbiome time to adjust.

If travelling, consider using hay cubes which provide more consistent quality.

5) Feeding mouldy feed

Mouldy hay is common in hot and humid conditions, but will cause serious problems for your horse’s gut and overall health.

Mould is a source of mycotoxins that can disrupt your horse’s microbiome and cause diarrhoea.

Avoid exposure of any feedstuffs to moisture by storing forage, supplements and hay in cool, dry, and dark environments.

Throw out any mouldy feed to reduce the risk of toxins entering your horse’s digestive system.

6) Abrupt changes to your feeding routine

Your horse’s digestive system is very sensitive to changes and the microbiome is easily disrupted when new feeds are introduced.

Sudden changes to your feeding routine disrupts the delicate balance of microbes in the digestive tract and can result in diarrhoea.

Horses are hindgut fermenters, meaning that they rely on bacterial populations in the hindgut to ferment fibres from forage so they can extract energy and nutrients from cellulose.

When new hays are introduced, this can alter the microbial populations in the hindgut and colon which can cause diarrhoea.

Make changes gradually over a period of two to four weeks.

This includes changing your horse’s forage or hay type, switching their concentrate source, or even adjusting mealtimes.

7) High intake of grains

Grains and concentrates, i.e. oats, barley, and corn, are high in non-structural carbohydrates (NSC) and are associated with looser stool. Non-structural carbohydrates include starches and sugars.

Your horse’s small intestine has a limited ability for digesting NSCs, and excess starches can enter the hindgut, resulting in a condition known as hindgut acidosis.

Diets that are too high in NSCs can cause dysbiosis and lead to diarrhoea.

Limit grains and concentrates when possible and provide fibre-rich grass/forage or hay as the main part of your horse’s diet.

Stressors are another common cause for diarrhoea.

Stress can lead to hormonal changes in your horse that can result in many digestive problems such as diarrhoea.

Hormonal responses can affect your horse’s appetite and result in reduced feed intake, as well as alter how the digestive system processes food.

Stress-induced diarrhoea is most commonly acute unless the stressor persists, in which case diarrhoea can become chronic.

The best way to prevent stress-induced diarrhoea is to eliminate or reduce exposure to the stressor.

Feeding management reduces the impact of stress-related diarrhoea when eliminating the stressor is not an option.

Digestive health supplements can benefit horses exposed to stressful conditions more frequently, such as athletic or working horses.

Ensuring proper hydration and electrolyte balance is also critical for these horses.

8) Stall confinement

Stall confinement of more than 12 hours per day can reduce colonic motility.

This slows the movement of food and liquid through the gut of your horse.

Research shows that stall-confined horses also consume less, even when forage or hay is readily available.

Eating less and moving around less can result in digestive problems such as ulcers, colic and diarrhoea.

9) Travelling and trailering

Travel is stressful for horses and can result in similar physiological effects as stall confinement.

Horses that are trailered often have inconsistent access to food and water while in transit.

While travelling, horses are confined and and can’t express normal species-appropriate foraging behaviours.

This lack of movement results in decreased gut motility and reduced movement of foodstuffs through the colon.

Horses that are being transported may require additional dietary support in the form of probiotics or other supplements to minimise the risk of gut problems.

10) Environmental stress

Environmental stress negatively affects digestion and can lead to diarrhoea.

Examples of environmental stressors includes loud sounds or unusual movements, changes in housing conditions, and changes to social dynamics.

Research shows that horses experiencing a spike in stress hormones (such as cortisol) are more likely to experience digestive issues including increase risk of gastric ulceration, colic, and diarrhoea.

These effects are mediated by inflammatory pathways that affect the microbiome and pH levels of the digestive system.

11) High-intensity exercise

Regular exercise is great for digestive health because it encourages the movement of food through the digestive tract and promotes hydration, but too much exercise leads to gut issues.

Frequent, intense or long exercise bouts can increase levels of glucocorticoid stress hormones and negatively impact digestion.

Intense exercise may contribute to diarrhoea by causing food to move rapidly through the intestines.

When gut motility is suddenly increased, absorption of nutrients and water from feed is compromised, which can overwhelm the hindgut.

12) Anaesthesia recovery

Stress from anaesthesia can impact the microbiome of horses, resulting in bouts of diarrhoea.

The effects of anaesthesia on digestive health are not well understood.

Horses receiving anaesthesia typically also undergo fasting and transportation, so it’s difficult to isolate the effects of anaesthesia, but since your horse’s bodily functions slow down during anaesthesia and getting the gut working again after waking up is a priority.

Stress affects your horse’s digestive health and can contribute to diarrhoea.

Bacterial infections can also cause diarrhoea in horses.

Bacterial infections can cause dysbiosis, resulting in diarrhoea and other symptoms such as fatigue, weakness, and loss of appetite.

Horses with bacterial infections may require intravenous supply of fluids and electrolytes to replenish fluid levels and prevent dehydration.

Horses may require treatment with antibiotics or prescription non-steroidal anti-inflammatory drugs.

Use of antibiotic medications can also contribute to diarrhoea as these drugs kill off both good and bad bacteria in the gut.

Probiotic supplements can help to replenish the microbiome during or following use of antibiotics.

13) Salmonella

A salmonella infection is one of the most commonly diagnosed causes of diarrhoea in adult horses.

This pathogenic bacteria releases toxins that cause inflammation in the intestinal lining.

Your horse may become infected by Salmonella through feed or water contamination, eating faeces that contain the bacteria, or contact with other infected animals.

Horses with salmonellosis may exhibit mild signs such as fever, weakness, low appetite and watery stools. In severe cases, diarrhoea can be bloody and fatal.

14) Clostridium

Clostridium is another pathogenic bacteria that can cause diarrhoea in horses, and these bacteria grow in the small and large intestines and the rectum of the horses.

Overgrowth of C. difficile and C. perfringens is linked to antibiotic use, food deprivation, and stress in horses.

Horses may be exposed to the bacteria through the faeces of a horse treated with antibiotics, the faeces of a foal with diarrhoea, or at a veterinary hospital.

Pathogenic bacteria can cause changes in the horse’s gut microflora and lead to diarrhoea.

Probiotics and antibiotics may be recommended by your veterinarian.

15) Parasitic infection

Internal parasites can be a serious problem for horses, resulting in diarrhoea, weight loss, weakness, fatigue, and swelling under the skin.

If you suspect your horse is affected by parasites, consult with your veterinarian.

Treatment should be administered as soon as possible to minimise adverse effects.

Internal parasite load management is critical with horses.

Regular faecal checks to determine parasite load and de-worming when necessary (as opposed to at regular intervals) will help to reduce parasite resistance to medications and make sure you only de-worm when it’s genuinely needed.

16) Larval cyathostominosis

Over 40 cyathostominosis species can infest the large intestine of horses resulting in watery stools and diarrhea.

The larvae from cyathostomes (small strongyles) become embedded in the large intestine encased within cysts.

Larval cyathostominosis occurs when the larvae emerge from the cysts and trigger an immune reaction that causes damage to the intestinal lining.

Grazing horses can ingest these parasites if they are foraging near manure piles and become infected.

Cyathostominosis infections can require anti-inflammatory drugs, fluid therapy, and other medications.

Parasites are spread through contact with infected faeces from other horses. In severe cases, infectious diarrhea caused by parasites can be fatal.

Environment and toxins also play a part in horse diarrhoea.

Toxins and other substances in your horse’s environment can result in diarrhoea if consumed in large amounts.

Certain poisonous plants contain chemicals that can disrupt gut function.

Excess use of medications can also result in toxicosis (any diseased condition caused by poisoning).

17) NSAID toxicity

Prolonged use of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) at high doses can result in NSAID toxicity.

Excessive use of NSAIDs can result in increased intestinal permeability, right dorsal colitis, and protein deficiencies, all of which can result in diarrhoea.

18) Ingesting sand

Sandy pastures, paddocks, and stalls can lead to sand ingestion in your horse. Sand can accumulate in the large intestine and disrupt the microbiome, potentially resulting in diarrhoea.

In serious cases, sand ingestion can lead to impaction and sand colic.

19) Toxic plants

Ingestion of the following plants can cause diarrhoea in horses and other serious side effects:

  • Buttercups
  • Oleander
  • Nightshade
  • Acorns
  • Yucca
  • Raw linseed oil
  • Castor oil

Ingestion of toxins, drugs and other environmental substances can cause diarrhoea.

Minimise the use of NSAIDs, pay attention to plants that grow in your pasture and avoid using ground feeders in sandy locations.

Disease and disorders can cause diarrhoea in horses.

In some cases of diarrhoea, the underlying cause can be a disease or disorder that affects the gastrointestinal system.

20) Free Faecal Water Syndrome

Diarrhoea may occur in conjunction with Free Faecal Water Syndrome (FFW).

Horses with FFW can experience two distinct phases of defecation: a solid phase in which solid faeces are eliminated and a liquid phase in which free water runs out of the anus before, during, or after the solid phase.

The cause of faecal water is unclear, but like diarrhoea, it may be a sign of leaky gut or dysbiosis.

21) Inflammatory Bowel Disease (IBD)

Yep, horses get this too!

Inflammatory Bowel Disease is an immune condition that can affect nutrient absorption and gut permeability.

Horses with IBD experience inflammation in the lining of the small intestine.

If the large intestine is also affected, diarrhoea can occur.

22) Hindgut ulcers

Ulcers are extremely common in horses, affecting between 60-90% of pleasure and performance horses.

Ulcers can cause horses to buck under saddle, so make sure you know your horse’s signs of pain.

Ulcers can occur in the oesophagus, squamous or glandular regions of the stomach, small intestine, and hindgut.

Diarrhoea can sometimes occur in conjunction with gastric ulcers, but this symptoms is more commonly associated with hindgut ulcers.

23) Gastrointestinal lymphoma (cancer)

This disease is extremely rare in horses, but can cause diarrhoea.

Horses affected by gastrointestinal lymphoma can exhibit symptoms such as weight loss, poor appetite, lethargy, abdominal pain and diarrhoea.

In some cases, diarrhoea may be a symptom of a more serious disease or disorder affecting the gastrointestinal tract of your horse.

Consult with your vet for appropriate treatment.

Diarrhoea in foals.

Diarrhoea is extremely common in foals as the immune system and gut microbiome are not yet well-established.

According to one study, 20% of foals experience diarrhoea within the first six months of life.

During the first few weeks of life, foals are particularly susceptible to infections, disease, and gut disturbances.

Some cases of diarrhoea in foals may resolve on their own without medical care or treatment.

Consult with your veterinarian to rule out other more serious causes of diarrhoea, particularly if the foal shows loss of appetite or seems dull.

24) Foal heat diarrhoea

Within the first four to fourteen days of life, foals may develop foal heat diarrhoea or scours.

This condition is believed to be caused by changes in the foal’s gastrointestinal tract with the addition of feed to the diet.

Foals may also come into contact with bacteria through ingestion of the mare’s manure (coprophagy), resulting in changes to the foal’s gut flora.

Foal heat scours will typically resolve over time as the hindgut microbiome is established.

25) Rotavirus

Foals younger than six months old are at high risk of contracting rotavirus, a contagious virus that is one of the most common reasons why foals experience diarrhoea.

Exposure to contaminated faeces is the main route of transmission for rotavirus.

If your foal has diarrhoea, keeping it away from other foals and horses can help to minimise the risk of contagious transmission.

26) Rhodococcus equi infection

Foals are susceptible to infection by Rhodococcus equi bacterium, which live in the soil.

This pathogen can cause pneumonia in foals.

Approximately one-third of foals affected by Rhodococcus equi experience diarrhoea as a symptom.

Foals showing respiratory or gastrointestinal signs of R.equi infection should be isolated from the herd to minimise spread of the virus.

27) Foals transitioning from milk to feed

As the foal begins to consume solid foods, like as hay, forage, and eventually grains and concentrates, their digestive system needs to adjust.

This transition is sometimes associated with diarrhoea, especially if the foal’s diet is changed abruptly.

Foals may also develop diarrhoea or loose stools as a result of feeding a milk replacement or cow’s milk.

Forages, grains and concentrates should be introduced as “creep feed” before the foal is weaned to help ease the transition away from milk and minimize digestive upsets related to weaning.

Foals are more susceptible to infections and dysbiosis as their microbiome is still being established. This puts them at increased risk of experiencing diarrhoea.

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