Looking after your horse’s liver
Professor Jo-Anne Murray
PhD, MSc, PgDip, BSc (Hons), BHSII, RNutr, PFHEA University of Glasgow Veterinary School
Why is the liver so important?
As we know from our own health, the liver is one of the most important organs of the body, and it’s the same in most mammals, including performance animals such as the horse. The liver is part of your horse’s digestive system and is one of the most metabolically active organs in the horse. It performs crucial roles as part of the overall digestive system in the horse: i) for those nutrients that flood in to the liver it plays a key role in regulating their metabolism, storage and distribution within the body; ii) it is one of the principal storage sites of glycogen, the so-called ‘animal version of starch’, which is one of the ways the body stores energy; iii) it is a key storage site for a host of other nutrients such as fats, proteins and some vitamins; iv) it essentially filters out the blood that comes out of the intestinal tract on it’s way back to the heart; v) it metabolises drugs and toxins ensuring that they are not as harmful to the horse; vi) it is crucial in its role for fat digestion, through the production of bile; and vii) it produces essential components that are key in the horses natural ability to clot blood when required.
When things go wrong
We are probably all aware of some diseases of the liver in humans, and equally your horse can be affected by liver disease and it comes in various forms. The horse liver is actually a relatively ‘robust’ organ that generally copes well with disease and tends to be fairly good at repairing itself, but there can be occasions when a horse’s liver is compromised, leading clinical symptoms that will not only impact on their health, but also on their performance. Horses can be affected by hepatitis, just like humans and other animals. Hepatitis is inflammation of the liver and that can occur as a result of many diseases or disorders.
The most common causes of liver disease are related to nutrition. For example, the ingestion of certain toxins can seriously affect the liver. This is particularly evident in horses that graze plants that contain compounds called pyrollizidine alkaloids (PA). A common example of a plant species that contains these toxic compounds is ragwort, but other plant species can also contain high levels of PA. More recently, veterinarians and nutritionists have also become more aware that in some horses with liver disease there also seems to be a link with exposure to mycotoxins (toxic substances found in certain types of fungi/moulds). Compared to many other species horses are particularly susceptible to mycotoxins and these can be associated particularly with conserved forage such as hay, haylage and silage, where they are not conserved, fermented (in the case of haylage and silage) or stored particularly well. Another liver condition related to diet that is common in horses is that of hyperlipaemia, which essentially means that there is excessive fat in the bloodstream. It is most commonly seen in obese horses, ponies and donkeys where their dietary intake has been purposely reduced suddenly and dramatically, or alternatively if these animals suddenly stop eating as much due