The lowdown on your horse’s liver

By Wendy Talbot on 04 June 2019

Your horse’s liver is big and very clever: it is your horse’s largest internal organ, weighing around 5kg and is thought to perform around 500 different functions. Unlike most other organs it also has a significant capacity to regenerate cells.

Where is the liver in my horse?

The liver sits centrally in your horse’s abdomen behind the diaphragm. At a microscopic level it is made up of lobules which consist of columns of cells around a central draining blood vessel. The hepatic portal vein and hepatic artery provide the blood supply and around 10% of your horse’s blood can be found in the liver at any one time.2,3,4

What does the liver do?

The liver is a versatile organ with numerous vital functions. It is key in supporting digestion and metabolism and also works as a filtration system to remove toxins ('detoxification').2,3

  • Digestion and metabolism

Bile, which is produced and secreted by the liver helps to process and absorb fats and fat-soluble vitamins. Carbohydrates are metabolised in the liver. Excess glucose from meals is stored as glycogen and converted back to glucose when blood sugar levels drop below normal.2,3,4

  • Detoxification

The liver filters and removes potentially harmful substances from the blood, to protect other organs in the body from damage. Naturally produced toxins, are also filtered; ammonia, which is produced from protein metabolism is converted into urea and excreted while bilirubin, which is an orange-yellow pigment formed from the normal breakdown of red blood cells, is filtered into bile for excretion into the gut.2,3,4

  • Other functions

Blood proteins are synthesised in the liver and it also stores certain essential vitamins and minerals and iron. It manufactures many essential micro-chemicals too, including factors essential for normal blood clotting and certain vitamins.2,3,4

What can cause liver disease?

  • Eating toxic chemicals or plants can result in damage to the liver and ragwort poisoning is one of the most well-known causes. The toxins in the plant cause the liver cells to merge together; eventually they lose function and are replaced by scar tissue. Ragwort poisoning is cumulative and the damage caused is irreversible.3,4,5
  • Infections can cause inflammation of the liver resulting in individual cells being destroyed and replaced with scar tissue.5
  • The liver can be damaged by a condition called hyperlipaemia, typically seen in overweight ponies with drastically reduced food intake, which results in an excessive amount of fat in the bloodstream.5

Signs of liver disease may include6

  • Weight loss
  • Diarrhoea
  • Excess fluid accumulation ('oedema')
  • Repeated yawning
  • Reduced performance
  • Reduced appetite
  • Deterioration in coat quality
  • Photosensitisation (excessive skin sensitivity to sunlight)

Treating liver disease

Usually at least 70% of the liver must be affected before signs of liver disease occur which means that early stages of disease can be challenging to diagnose. A liver biopsy can be helpful, together with blood tests and ultrasound scans. Treatment and recovery very much depend on the initial cause. Treatment may involve antibiotics, steroids, and vitamin supplements. In severe cases hospitalisation and intravenous fluids may be required. Many horses with liver disease go on to make excellent recoveries.5,6

It is important to contact your vet immediately if you think your horse may have any signs of liver disease.


Did you know?

The liver accounts for roughly 1% of your horse’s bodyweight.6

Hepatitis means inflammation of the liver






Wendy graduated from Bristol University in 1999. She then went on to complete a residency at Liverpool University and holds a European Diploma in Equine Internal Medicine. After working in practice for 13 years, she joined Zoetis in 2012 as the National Equine Veterinary Manager.

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