Bronson, DVM: Metabolic Disorder

By Dr. Joanna Bronson | http://bronsonvetservices.com/ Metabolic issues can be observed by certain physical signs:

· Chronic or recurring laminitis (in the absence of any other cause)

· Variations in weight.

· Abnormal fat pockets found along the crest of the neck, the rump and tail head, and the abdominal area

· Symptoms of Insulin Resistance include excessive thirst, drinking large amounts of water, and frequent urination.

· Symptoms of PPID/Equine Cushing’s include increased coat length, delayed shedding in the spring, excessive sweating, and lethargy, excessive thirst and urination.

· Muscle wasting

Affected horses are susceptible to skin infections, intestinal parasites, and dental disease. Some may even develop neurological signs or changes in behavior with Cushing’s but not EMS. PPID or Equine Cushing’s Disease is one of the most common endocrine diseases found in horses. It usually appears in equines 15 years of age and older with the average age being 20 or older. It can occur in younger horses but is rare. This complex condition originates from an abnormal function of the hormone-producing pituitary gland that lies at the base of the brain. Usually, a mass develops that crowds the surrounding tissue causing neurological signs to then appear. Affected horses lose the daily natural rhythm of the hormone cortisol. Its usual production is high in the morning and low at night. Loss of this rhythm can be triggered by stress, disease, and old age. Unfortunately, many equines that develop PPID will often also develop a form of laminitis which is different from pasture or stressrelated laminitis. However, if PPID is caught early before laminitis appears, it may be more easily controlled than if it originated through the other causes.

If a horse is suspected of having PPID, the first line of testing involves an ACTH (adrenocorticotrophin hormone) test. In affected horses, this hormone is found in higher concentrations than normal.

Once diagnosed, the standard treatment for PPID is the drug Pergolide given orally once daily. The prescribed dosage may be higher initially and may take several months to adjust. Yearly testing is necessary for continued correct diagnosis, but lifelong treatment is necessary. If the horse has also developed laminitis, control often means remedial shoeing or trimming. An appropriate diet must be enforced with limited or no access to pasture and careful stable management with clean, thick bedding.

These horses should also be tested for EMS (Equine Metabolic Syndrome) as unchecked EMS can prevent good control of laminitis in equines with PPID. Prognosis for horses and ponies affected with PPID are most generally favorable. With appropriate management and diet, the signs should improve. After therapy has begun, repeat testing of ACTH should show a reduction in blood concentration levels. Hypothyroidism in horses is characterized by a deficiency of thyroid gland activity through underproduction of the hormone thyroxin. Thyroid conditions are caused by too much or too little iodine which can affect the horse in many ways, including: · The inability to regulate body temperature · Affecting the body's use of protein · Heart rate and strength · Production of red blood cells · Reproduction · Hair coat · Energy levels · Appetite · Milk production · The immune system · Usually overweight

In foals, the thyroid hormone is essential for the normal development of the musculoskeletal and nervous systems. Hypothyroidism is classified as being primary, secondary, or tertiary. Primary hypothyroidism originates from a disease of the thyroid gland and is the most common. Secondary hypothyroidism is caused by a deficiency of the thyroid-stimulating hormone, usually as a result of a lesion in the pituitary gland. Tertiary hypothyroidism is caused by a lack of synthesis or release of thyrotropinreleasing hormone. The thyroid is being produced, but the body is unable to use it.

Common causes are iodine deficiency (found most around the Great Lakes regions) or excess (goiter), inflammation of the thyroid gland, cancer of the gland, developmental failure of the thyroid to grow, or ingestion of plants or toxins that interfere with the body's ability to make the thyroid hormone.

Lifestyle changes are important to avoid metabolic complications. Effective management tips include:

· Increased exercise and feeding a reduced-calorie diet

· Limiting pasture grazing (or using a grazing muzzle)

· Not feeding grains, carrots, apples, or sweet feeds

· Avoiding supplements that are soybean meal-based or high in sugar content

· Testing hay for carbohydrate content. Non-structural carbohydrate content should be under 10%. Soaking hay for 15-60 minutes, then dumping water prior to feeding can help remove nonstructural carbohydrates

Metabolic disorders in horses are serious and always need to be addressed promptly. Dr. Joanna Bronson graduated from MSU at the top of her class. In 2005, she opened Bronson Veterinary Services in Coldwater, MI, a full-service equine, small animal hospital and surgical center.

(517) 369-2161

452 W. Central Rd., Coldwater, MI 49036 http://bronsonvetservices.com/