10/19/2026
Hyperlipemia and Hepatic Lipidosis in Equids
Brian S. Burks, DVM
Diplomate of the American Board of Veterinary Practitioners®
394 Fox Road
Apollo, PA 15613
(724) 727-3481
www.foxrunequine.com
Cresty necks. Fat deposits. Everyone loves those cute, round little ponies in the field, but there is danger lurking in these equids. All that fat can become a problem, causing severe, life-threatening illness. This occurs most often in ponies, miniature horses, donkeys, and miniature mules. Other breeds are sometimes involved, including the Quarter Horse, Paso Fino, Icelandics, and Tennessee Walking Horse.
All that adipose tissue can break down, causing hyperlipemia and hyperlipidemia. These conditions are those of increased triglycerides (TG) in the blood. The former refers to a level of 500mg/dl or greater and carries a worse prognosis. The blood is often grossly lactescent or fatty. The liver may become infiltrated, causing hepatic lipidosis.
Affected equids are usually, though not always, obese, and have a recent history of stress, illness, weight loss, or pregnancy/lactation. There may be an inability to provide for metabolic demands or malnutrition. Parasitism is another risk factor. Being female doubles the risk of hyperlipemia.
Most species use energy in the form of glucose, as do equids; however, the horse depends upon absorption of volatile fatty acids as their major energy source. Glucose is then manufactured from VFAs in the liver and is stored in the liver (and muscle) as glycogen. Energy is also stored in adipose tissue in the form of triglycerides, which can be broken down to fatty acids when there are additional energy requirements not met by intake. Hormone Sensitive Lipase (HSL) is activated during times of low energy- glucose and insulin levels are low- to break down adipose, supplying the body with energy reserves. These fatty acids are taken to the liver for gluconeogenesis- making new glucose. Other species also make ketones, but the horse generally does not. Lipoprotein lipase is the enzyme responsible for the removal of VLDLs from circulation into adipose tissue. Its activity is maximally increased during lipolysis; thus it is the over-production of VLDLs, and impairment of their removal is responsible for hyperlipemia. Hormones such as adrenaline and cortisol, released during times of stress, speed up lipolysis, increasing the magnitude of TGs in blood and the liver.
Obesity provides excessive adipose tissue stores of fatty acids, which are available for rapid mobilization into the blood stream. This is triggered by stress or a negative energy balance.
Triglycerides are put into a lipoprotein called Very Low-Density Lipoprotein (VLDL) for transport in aqueous solution (blood). When food is withheld, more fatty acids are released, and more TGs are exported to the liver. This can overwhelm the liver’s ability to process the TGs and hepatic infiltration of fat occurs, called hepatic lipidosis. Increased levels of TGs and VLDLs can be measured in blood. The liver is in good company, as other organs may also have TG infiltration, especially the kidney, leading to acute renal failure.
Many times, these equids are insulin resistant. Insulin drives TGs into adipose tissue, reducing their blood levels, but if the insulin does not work well, blood levels of TGs and glucose elevate. Phenotypically, ponies and miniatures are often insulin resistant naturally, due to the environments in which these breeds developed- sparse food in the winter months. This is accentuated by obesity. Insulin insensitivity results in higher rates of adipose lipolysis, increased fatty acids, VLDL, and TG blood levels. Studies have correlated increased insulin values with obesity, or simply being overweight. Insulin resistance is also a feature of pregnancy, especially in late term.
Equids with hyperlipemia often have an underlying disease condition, including enterocolitis, endotoxemia, parasitism, infection, equine Cushing’s disease, renal insufficiency, and neonatal septicemia. Clinical signs include anorexia, lethargy, weakness, severe depression, ataxia, colic, diarrhea, fever, and dependent edema. There may be weight loss, reluctance to walk, and incoordination. Hepatoencephalopathy, and even sudden death from hepatic rupture may also occur.
Diagnosis is based upon signalment, history, and blood work. Being a pony or miniature, and especially being female, increases the likelihood of hyperlipemia. A history of recent stress or illness is supportive. Blood work may reveal active infection, and provides information about renal and hepatic function, with elevated BUN and creatinine or increased liver enzymes (GGT, SDH, ALKP) Triglyceride levels can be measured directly. Electrolyte levels may be abnormal as well.
Treatment involves the following:
1. Treatment of hepatic disease if present
2. Positive energy balance
3. Treatment of concurrent disease and removal of stress
4. Inhibition of lipolysis
5. Increased TG uptake by peripheral tissues.
Good quality concentrate and hay should be provided. Anorectic animals need to be fed via nasogastric tube, usually with a commercially available formula that will pass through the tube. It is difficult to dissolve complete feeds and get them through a tube. Parasitism, chronic (or acute) infection, and musculoskeletal disease should be treated. Insulin antagonizes lipolysis and stimulates tissue uptake of carbohydrate, helping to decreased TG in the circulation and liver.
The prognosis for equids with hyperlipemia is poor. Mortality is around 60%, but the prognosis is variable and is better with prompt treatment. Death is often from the underlying disease, not hepatic lipidosis. Miniatures with triglyceride levels less than 1200 mg/dl are more likely to survive. Prevention is by providing adequate nutrition and exercise to prevent obesity. Good, routine healthcare is important to minimize illness from infectious and viral diseases and to prevent high loads of parasites.
Prevention of hepatic lipidosis involves identification of at-risk equines, including pregnant or lactating mare, obesity, geriatric ponies, and donkeys, or those with underlying illness such as parasitism or diarrhea. Such animals should be tested for equine Cushing’s disease and equine metabolic syndrome.
Fox Run Equine Center
(724) 727-3481
