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Veterinarians report that they are treating more horses for hyperlipidemia, potentially as a result of modern sedentary lifestyles and the feeding of high-carbohydrate diets. [1]
This life-threatening condition commonly occurs in ponies, miniature horses, and donkeys with insulin resistance. It is linked to equine obesity and metabolic dysfunction, but can be prevented through feed and management practices.
Hyperlipidemia typically occurs when horses are in a negative energy balance due to restricted feed intake. This calorie deficit results in stored fat (lipids) being broken down and mobilized into the blood to be used for energy.
In horses with hyperlipidemia, blood levels of triglycerides become too high and cause negative effects for the liver, kidney and overall metabolic health.
This condition is difficult to recognize, but should be suspected in metabolic horses on a restricted diet that become disinterested in food. If your horse shows these signs of hyperlipidemia, consult with your veterinarian to obtain a diagnosis and a treatment plan.
Our nutritionists can help you formulate a diet to support your horse’s metabolic health and reduce the risk of this condition.
What is Equine Hyperlipidemia?
Hyperlipidemia means too much fat in the blood. This is mainly due to high levels of triglycerides.
In horses, this condition is diagnosed when triglyceride concentrations exceed 500 mg/dL in the blood (serum). Normally triglyceride levels are less than 100mg/dL. [2]
This occurs when adipose tissue (which stores fat) does not function properly and releases too much fat into circulation.
This results in a vicious cycle of reduced insulin sensitivity which leads to an even greater increase in triglycerides within the blood. There can also be effects on the brain including depression and anorexia (lack of appetite). [1]
As more and more lipids and triglycerides accumulate in the blood, severe complications include hepatic and renal lipidosis. [1]
Causes of Hyperlipidemia in Horses
During periods of starvation, the horse’s body is designed to tap into stored fat for energy.
When food is sparse, the horse enters into a negative energy balance meaning that more calories are burned than are consumed. The body meets additional energy demands by mobilizing fat deposits into the bloodstream.
This is a normal physiological response that continues until the horse finds food and returns to a positive energy balance.
However, this response can become exaggerated and inappropriate in horses on a severely restricted weight loss diet or in horses affected by metabolic dysfunction. [1]
In these horses, adipose tissue is mobilized and fatty acids are converted into triglycerides in the liver leading to high levels of triglycerides in the blood. The triglycerides are packed in particles called low density lipoprotein (LDL) and the numbers of these particles also increase, affecting metabolic pathways.
Typically, hyperlipidemia occurs within 40 hours of feed restriction. This is the time it takes for free fatty acids to get converted into triglycerides. [2]
In a study of overweight Caspian miniature horses, hyperlipidemia occurred within 48 hours of feed deprivation.
This condition can also be triggered by: [3]
- Extreme exercise
- Physiological stress
- Disease or illness
- Pain
- Feed changes
- Transportation
Horses at Risk of Hyperlipidemia
Any horse can develop hyperlipidemia if they are put on a severely restricted diet or undergo extreme exercise or stress.
Horses with insulin resistance or equine metabolic syndrome are at the highest risk of hyperlipidemia because they are already affected by metabolic dysfunction. Obese horses are also at higher risk of this condition. [4]
Pregnant and nursing mares, horses with higher nutrient demands, and horses affected by illness are also at risk of negative energy balance and could develop hyperlipidemia.
The most common horse breeds affected by hyperlipidemia are ponies, miniature horses, and donkeys. These breeds may have a genetic predisposition for obesity and metabolic issues. [1][2]
Signs & Symptoms
The main signs of hyperlipidemia to watch for when your horse is on a restricted diet include:
- Anorexia (no appetite)
- Lethargy and weakness
- Fever
- Ataxia (lack of muscle control)
- Depression
- Jaundice
- Abdominal swelling
- Diarrhea
- Dysphagia (difficulty swallowing)
Anorexia is the most common symptom seen in hyperlipidemic horses. A horse with hyperlipidemia will have zero interest in any food – even their favourite treats.
Anorexia can also be a sign of other conditions – such as colic – so it does not necessarily mean they have hyperlipidemia.
If in doubt about your horse’s health, call your veterinarian.
Diagnosis
Your veterinarian will diagnose hyperlipidemia after gathering information about your horse’s health history, diet, and condition from a physical exam.
Your veterinarian will also want to know about any of the clinical signs mentioned above.
Finally, they will perform a blood test to confirm diagnosis. Blood with an opaque appearance or plasma with a triglyceride level of greater than 500 mg/dL (5.6 mmol/L) indicates hyperlipidemia. [3]
How to Treat Hyperlipidemia in Horses
If you suspect your horse has hyperlipidemia, contact your veterinarian immediately.
Your veterinarian will first assess whether your horse is in a negative energy balance and will attempt to correct this by encouraging the horse to eat forage or other feeds.
If this is not possible, they may feed your horse by placing a nasogastric tube, which is a feeding tube that goes through the nose to the stomach. Another food replacement method is known as total parenteral nutrition and involves bypassing the digestive tract and giving nutrients intravenously.
Insulin will be administered to your horse to help control insulin dysregulation and encourage fat storage into adipose tissue. [1]
Your veterinarian may also administer fluids to help dilute your horse’s blood and reduce serum triglyceride concentrations. These fluids may contain dextrose – a sugar which goes straight into your horse’s circulation to improve energy balance.
Medications may be required to support liver function and reduce inflammation. Anti-coagulants may be used to thin your horse’s blood.
Hyperlipidemia is an extremely serious condition. A review of 23 cases in miniature horses found an overall mortality rate of 39%. [5]
Prompt and veterinarian attention is required to increase your horse’s chance of survival. Typicaly mortality rates are reported between 43 – 80% but this can be reduced to 0 – 33% by aggressive treatment. [1]
Obesity in Horses
With up to 70% of the equine population now classified as overweight or obese, it is common to find horses on a restricted diet to promote weight loss. [6]
However, care must be taken when restricting your horse’s calorie intake as sudden or harsh restrictions can lead to hyperlipidemia.
Obesity is the result of a long-term positive energy balance, characterized by the horse consuming more energy than it expends.
Excess energy is stored as fat in adipose tissue around the body. Fat distribution can be internal (such as visceral fat surrounding organs), subcutaneous (under the skin), or regional to a specific area as seen with cresty neck.
With prolonged positive energy balance fat also gets stored in other tissues that are not intended to store fat, such as the liver and muscle. This causes metabolic dysfunction such as insulin resistance in these tissues.
Horses are classified as overweight or obese if they have a body condition score (BCS) of 7 and up on the 9-point Henneke scale, with greater than 20% of bodyweight consisting of fat.
Horses that carry too much fat can experience health complications linked to inflammation and oxidative stress. Excessive body fat also results in: [7]
- Increased strain on joints, tendons, ligaments, and muscles
- Stimulation of the hypothalamic-pituitary-adrenal (HPA) axis
- Chronically elevated cortisol levels
- Vascular dysfunction
Obesity is also a major risk factor for several other conditions and can contribute to: [7]
- Equine metabolic syndrome (EMS)
- Insulin dysregulation
- Laminitis
- Osteoarthritis
- Cardiovascular issues
- Hyperthermia (heat stroke)
- Infertility
- Poor performance
Some horses have a genetic predisposition to obesity. This includes native ponies, cob-type breeds, draft horses, miniature horses, and donkeys. [8]
These easy keeper breeds need to have their diets carefully managed to ensure a neutral energy balance is maintained.
Preventing Hyperlipidemia
Hyperlipidemia in horses is largely preventable, given the right feeding and management practices.
Assessing your horse’s individual risk, feeding adequate forage, and closely monitoring body condition are some of the ways that you can reduce the risk of this condition as well as other forms of metabolic dysfunction.
1) Assess your Horse’s Risk Level
The first thing to consider is whether your horse is in a high-risk category for developing hyperlipidemia.
Does your horse have a genetic predisposition to hyperlipidemia? Answer yes if your horse is one of the following:
- Miniature horse
- Donkey
- Native pony
Is your horse overweight or obese with a body condition score of 7 or greater? Does your horse have a metabolic condition including:
- Insulin dysregulation/resistance
- Equine metabolic syndrome
Has your horse experienced extreme stress? Do they engage in extreme physical exercise (i.e. racehorses post-racing)?
Finally, is your horse in a negative energy balance? Horses at risk of this include:
- Horses on a restricted diet
- Pregnant mares
- Lactating mares
- Sick horses (i.e. following colic surgery or colitis)
- Horses with poor appetite
Once you know your horse’s individual risk profile, you can determine how aggressively you need to adopt the following preventative strategies.
2) Feed Adequate Forage
When dieting your overweight horse, aim for a slow reduction in weight and ensure they receive adequate forage.
Drastic feed restriction results in sustained release of lipids that eventually leads to hyperlipidemia.
Avoid rapid weight loss by aiming for weight loss of around 1% each week. Closely monitor and track your horse’s weight and body condition score on a weekly basis. [9]
Horses should be fed a minimum of 1.5% of their bodyweight in forage per day (unless on the advice of your veterinarian).
For a 500 kg (1100 lb) horse, this means feeding a minimum of 7.5 kg (16.5 lb) of forage per day.
If you are feeding soaked hay, a mature low-sugar hay or straw, 2% of your horse’s bodyweight can be fed per day to achieve weight loss. [10]
3) Follow The Golden Rules of Feeding
In addition to feeding a forage-first diet, you can also support your horse’s metabolic health by eliminating excess sugars and starches in the diet. Avoid grain-based concentrates and high carbohydrate feeds, which can worsen insulin resistance.
Provide your horse with many small meals throughout the day rather than intermittently feeding large meals. Intermittent feeding practices can also increase the risk of gastric ulcers.
Feed according to your horse’s workload and bodyweight. A nutritionist can help you calculate your horse’s individual needs.
Finally, make all feeding changes gradually. Horses are particularly sensitive to change. Major alterations in the feeding program can trigger hyperlipidemia.
4) Vitamins and Minerals
Overweight horses may require fewer calories in their diet, but they still require the same quantity of vitamins, minerals, and protein as other horses of the same weight and workload.
A concentrated forage balancer or vitamin and mineral supplement will help you meet your horse’s daily requirements without adding unnecessary calories to the diet.
Mad Barn’s AminoTrace+ is a balanced vitamin and mineral supplement that is specifically targeted to the needs of metabolic horses, with higher levels of key nutrients including zinc, copper and magnesium.
AminoTrace+ supplies 20 mg of biotin, high levels of natural vitamin E, a full B-vitamin profile as well as added amino acids and 100% organic trace minerals. It comes in a low-NSC pellet and is designed to balance the majority of forage- and grain-based diets.
5) Body Condition Score
When on a restricted diet, it is important to assess your horse’s body condition weekly. Unexpected changes in body condition could indicate anorexia or other health problems.
You should aim to maintain your horse at a body condition score of 4-5 on the 9-point Henneke scale. A BCS of 3 or less is underweight and a score of 6 or more is overweight.
6) Seek Professional Help
If your horse is struggling to lose weight, ask your veterinarian to test for metabolic conditions such as EMS and insulin dysregulation.
Metabolic conditions increase the risk of hyperlipidemia and can make it more difficult to lose weight.
Consult with a nutritionist to design a balanced feeding plan for your horse to support weight loss. You can submit your horse’s information online and our nutritionists can assist you for free.
Conclusion
Hyperlipidemia is a potentially dangerous, hard to treat condition with a guarded prognosis.
As the prevalence of equine obesity increases, cases are now on the rise. However, this condition is entirely preventable with the right nutrition and management strategies.
For further information, read our article on how to body condition score your horse.
If you would like help formulating a weight reduction feeding program for your horse, submit their information online for a free consultation with our equine nutritionists.
References
- McKenzie, H.C. Equine hyperlipidemias. Veterinary Clinics: Equine Practice. 2011.
- Seifi, H.A., Gray, H., Mohri, M. and Badiee, A. Hyperlipidemia in Caspian miniature horses: effects of undernutrition. Journal of Equine Veterinary Science. 2002.
- Equine Hyperlipidemia. Horse DVM.
- Pösö, A.R., Viljanen‐Tarifa, E., Soveri, T. and Oksanen, H.E. Exercise‐induced transient hyperlipidemia in the racehorse. Journal of Veterinary Medicine Series A. 1989.
- Mogg, TD. Palmer, JE. Hyperlipidemia, hyperlipemia, and hepatic lipidosis in American miniature horses: 23 cases (1990-1994). J Am Vet Med Assoc. 1995 Sep 1;207(5):604-7.
- Menzies‐Gow, N.J., Harris, P.A. and Elliott, J. Prospective cohort study evaluating risk factors for the development of pasture‐associated laminitis in the United Kingdom. Equine veterinary journal. 2017.
- Rendle, D., McGregor Argo, C., Bowen, M., Carslake, H., German, A., Harris, P., Knowles, E., Menzies-Gow, N. and Morgan, R. Equine obesity: current perspectives. UK-Vet Equine. 2018.
- Harris, P.A., Bamford, N.J. and Bailey, S.R. Equine metabolic syndrome: evolution of understanding over two decades: a personal perspective. Animal Production Science. 2020.
- King, C. and Mansmann, R.A. Preventing laminitis in horses: dietary strategies for horse owners. Clinical Techniques in Equine Practice. 2004.
- McGowan, C.M. et al. Dietary restriction in combination with a nutraceutical supplement for the management of equine metabolic syndrome in horses. The Veterinary Journal. 2013.
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