Question and Answer with Dr. Moore
From what I understand, hyperlipemia is a rare blood disorder. This condition occurs in overweight equines or those that undergo a fast change in their diet. Equines with this condition will have very high amounts of fat in their blood. This can cause the liver to work absurdly, resulting in the process of liver failure. Symptoms of this disease include slowness, lethargy, loss of appetite, severe weight loss, and abnormal behavior. My question is, if you have an overweight horse/pony, what measures would you take to quickly reduce their weight before this condition occurs, but also decreasing it slowly enough that it doesn’t cause this condition to happen from the sudden change?
Dr. Moore’s Answer:
Hyperlipidemia also known as hypertriglyceridemia occurs when there is a negative energy balance (underlying illness, pregnancy, lactation, sudden starvation) or physiological stress (parasites, transport) in the horse. Ponies, miniature horses and donkeys are most susceptible. Many horses with insulin resistance (equine metabolic syndrome and some PPID horses) have hypertriglyceridemia so special attention has to be made to address the underlying condition. As you mentioned, it is a challenge to take an overweight horse (likely with equine metabolic syndrome) and help it lose weight but also prevent it from developing hypertriglyceridemia. For many, we use a three pronged approach; diet, exercise and levothyroxine.
The recommendations for weight loss in horses is to aim for 0.5% to 1.0% body weight loss weekly. This is done by feeding a grass hay, with NSC <10% at 1.4-1.7% body weight . Some horses are resistant to losing weight ( like people). We aren’t sure why but they need a slightly greater reduction in feed at1.15% body weight.
Along with diet, an exercise program should be instituted. This is barring any issues with laminitis ( which would have to be addressed first). Horses (ponies) should be exercised at a low to moderate intensity (canter) for >30 minutes a day 5-7 days a week. Checking the pulse or using a heart rate monitor will held with the intensity and heart rates should be around 130-150 beats per minute. Lower intensity (trot to slow canter) is used for those with previous laminitis and done on a soft ground (heart rate 110-130 bpm). Discontinue and have your vet assess if there is any lameness. This exercise can be ridden or unridden.
Levothyroxine is used to improve insulin sensitivity in these horses but should only be done with veterinary supervision. Horses need to be weaned off of this medication as the horse’s own thyroid gland will reduce making the hormone when an external source of the hormone is fed.
Triglyceride levels in the blood can and should be monitored if there is any question regarding how the horse is adapting to these management changes.