Common Causes of Muscle Atrophy in Horses

Our first topic is muscle atrophy in horses. This 3-part post discusses the causes of muscle atrophy, how atrophy is diagnosed and how it can be treated.

Muscle atrophy is defined as a reduced size or shape of skeletal muscles. Reduced muscle mass can affect the horse’s overall health and performance. While muscle atrophy can occur in various muscle groups, the most affected areas include the cervical, thoracolumbar, and pelvic regions. The causes of muscle atrophy in horses may be related to trauma, poor nutrition, a general lack of exercise, or an underlying systemic disease.

  1. Inadequate exercise or limited turnout: One of the primary causes of muscle atrophy in horses is a lack of exercise. Regular and appropriate exercise is vital for maintaining muscle strength and mass. Limited turnout or stall confinement can result in reduced movement and physical activity, leading to muscle atrophy. Reduced muscle activation can lead to muscle wasting and weakness.
  2. Poor nutrition: Adequate nutrition and a well-balanced diet play a significant role in muscle development and maintenance. Horses that do not receive appropriate levels of protein, carbohydrates, fat, or essential vitamins and minerals are prone to muscle atrophy. Poor nutrition can be due to a lack of access to food (e.g., starvation), low-quality foodstuffs, inability to properly chew (e.g., dental pain), or abnormal digestion (e.g., chronic diarrhea). Once the underlying nutritional deficiency is corrected, affected horses can regain their normal muscle mass quite rapidly.
  3. Trauma and injuries: Pain is a common cause of muscle atrophy. Acute pain induces a reflex inhibition of muscles, which serves as a protective mechanism to help guard and reduce movement of the injured area. Chronic joint or muscle pain will cause persistent changes in muscle function where some muscles have less activity (i.e., inhibited) and other muscles are required to work harder to compensate for those muscles that are not working properly. Improper saddle fit and incorrect riding techniques can also contribute to muscle atrophy.
  4. Degenerative and infectious conditions: Certain disease processes affect the nerves that innervate muscles or the muscle itself. Equine polysaccharide storage myopathy (PSSM) can directly affect muscle development due to abnormal carbohydrate metabolism. Equine motor neuron disease (EMND) is caused by a vitamin E deficiency, which leads to the degeneration of motor neurons and subsequent muscle atrophy. Equine protozoal myeloencephalitis (EPM) is a neurologic disease caused by a parasite that infects the brain and spinal cord in horses, causing localized muscle atrophy.
  5. Age-related factors: As horses age, they naturally experience some degree of muscle loss, known as sarcopenia. Older horses may also have diminished mobility and exercise capacity, which further exacerbates muscle atrophy. Regular exercise and proper nutrition become even more crucial for maintaining muscle strength and countering the effects of aging.

Muscle atrophy in horses can have various underlying causes, each of which requires careful consideration and attention. A lack of exercise, poor nutrition, age-related factors, injuries or lameness, and ill-fitting saddles or tack can all contribute to the development of muscle atrophy. By understanding these causes, horse owners, trainers and caregivers can take proactive measures to prevent muscle atrophy and promote the overall health and well-being of horses.

Read the complete 3-part series: Muscle Atrophy in Horses

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Resources

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Browse our RACE-approved catalog of online learning modules.