Performance horses require fitness training, careful management, and balanced nutrition to support stamina and recovery. As a result, owners and managers of these horses are always on-the-lookout for an “edge” in the form of novel exercise strategies and dietary supplementation. 

While racing involves intense short-term demands, endurance racing can involve horses covering up to 100 miles in a single day. During training and competition, endurance horses can have up to 60% higher energy demands compared to nonworking horses.¹ Additionally, heavily exercised horses of all disciplines are at higher risk of issues such as gastric ulcers and hindgut acidosis, which can impact their performance.

The word “endurance” references the capacity to withstand fatigue. Racing horses are usually able to supply enough oxygen to their tissues to support aerobic metabolism throughout an event. Horses in sprinting disciplines however, must rely on anaerobic processes.² Aerobic metabolism produces less lactic acid compared to anaerobic metabolism, thus horses are able to sustain this level of exercise for prolonged periods of time.

Fatigue in horses during long-distance exercise can arise from several factors including:

• Low energy reserves
• Lactic acid production
• Electrolyte imbalance
• Fluid loss
• Central fatigue¹

Horses and other mammals store energy in the form of glycogen in muscle and liver and as fat. Glycogen is a branched structure of glucose molecules. During exercise, glycogen and fat are broken down to make energy in the form of adenosine triphosphate (ATP). This facilitates muscle contraction and other processes involved in exercise. Glycogen provides a rapidly-available source of energy however, glycogen stores can be depleted by 50 – 75% in a mild endurance ride.² This means that the horse will have to rely on stored fat, amino acids, and dietary sugar to extract energy. Fatigue arises when blood glucose levels are low and amino acid breakdown is accelerated.

Using high-quality feed, digestible fiber sources and adding fat to the horse’s diet are some ways that owners and managers meet the needs of performance horses. Supplementing amino acids as well as essential vitamins and minerals has also become a popular regimen for improving stamina in equines.

Carnitine (L) for Horses

Carnitine (L) (also known as L-Carnitine or Levocarnitine) is a naturally-occurring amino acid that is made in the liver. This amino acid helps reduce lactic acid in the muscle and uses fat to burn as energy. By supplementing with carnitine, a horse is able to increase stamina and lessen recovery time. Performance horses can benefit from supplementation with L-carnitine, since exercise significantly increases the demand on muscles to produce energy from glucose, glycogen and fats. A high quality L-carnitine supplement can help horses better adapt to training, reduce muscle soreness, and shorten recovery time.²

L-Carnitine in horse supplements is believed to provide an important nutritional link in exercise recovery due to its role in fatty acid oxidation and energy metabolism. Feeding and supplementing animals with critical nutrients like L-carnitine promotes overall performance and muscle health, while optimizing recovery from oxidative stress, in both the short- and long-term.

L-Carnitine may be useful as adjunctive therapy for dogs with cysteine or urate urolithiasis   and dilated cardiomyopathy (DCM). Since it is an important nutrient that acts as a transport for fatty acids, essential for the cellular production of energy, deficiency of this nutrient can cause a variety of health problems for animals. Most notably, it is associated with heart cardiomyopathy in dogs, particularly large breeds such as Great Danes.³ L-Carnitine may also protect against doxorubicin-induced cardiomyopathy in dogs.^2,3

In cats, L-Carnitine has been recommended as a useful adjunctive therapy in feline hepatic lipidosis by facilitating lipid metabolism, but its use for this indication is somewhat controversial.³

L-Carnitine facilitates the entry of long-chain fatty acids into cellular mitochondria, where they can be used during oxidation for energy production. Cardiac and skeletal muscle are significant sites for L-Carnitine storage and activity.^2,3Severe chronic deficiency of L-Carnitine is believed to be the result of an inborn genetic defect where L-Carnitine utilization is impaired, as opposed to being the result of dietary insufficiency. Effects seen in L-Carnitine deficiency may include hypoglycemia, progressive myasthenia, hepatomegaly, DCM, hepatic coma, neurologic disturbances, encephalopathy, hypotonia, and lethargy.³

Where to buy Carnitine (L)

Carnitine (L) (L-Carnitine) is available in the U.S. through pharmaceutical manufacturers and through veterinary custom compounding companies. CARNITINE (L) 200 MG/ML, INJECTABLE SOLUTION, 100ML by NexGen Pharmaceuticals is an excellent adjunct to dietary supplementation to improve stamina in performance horses.

Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

¹equusmagazine.com.

²fei.org.

³Plumb’s Veterinary Drugs.