About Anhidrosis

Submitted by Reata on Sat, 10/10/2009 - 12:56

Anhidrosis the inability to sweat effectively.

General Information:

Sweating is the main way in which horses stay cool.
Heat dispersed via the respiratory tract in exercising horses may account for 15% to 25% of total heat loss.
Evaporation of sweat accounts for up to 65% of their heat loss.
In this regard, it has been calculated that evaporation of 1 liter of sweat can dissipate the amount of heat generated in I to 2 minutes of high-intensity exercise by horses.
Occasionally a horse’s ability to sweat can be impaired. It usually occurs in the hot summer months.
The exact cause is not well understood but the most probable cause is altered sweat gland production resulting from overstimulation.
Concurrent low blood electrolytes, especially potassium may play a roll.

Affected horses show little or no sweating
Elevated respiratory rate, and heart rate
Dry and flaky skin with hair loss, especially in long standing cases.
Lethargy
Decreased water intake
Sometimes an elevated body temperature during minimal exercise
Sometimes an elevated body temperature at rest when the ambient temperature is high.
Decrease performance with labored breathing
Anhidrotic horses may prefer to be near the water or in the shade during the hot part of the day and may stand submerged in water troughs or attempt to splash water on their bodies to cool themselves.

Solid environmental management is the only reliable treatment option at the present time.
Supplemental electrolytes, especially potassium salts can be added to the feed.
Some anecdotal reports of success with iodinated casein (10-15 g/day for 4-8 days) and with oral vitamin E (natural alpha tocopherol) fed at the rate of 1000-3000 IU per day for 1 month.
Amino acid supplementation with tyrosine may help with the resensitization of the sweat gland receptors.
A commercially available product (One AC) containing tyrosine has had some success in
controlling symptoms in Arizona horses with anhidrosis:

              MPCO, LLC
                2905 W. Cholla
                Phoenix, AZ
                602-866-7701 or www.SmartPakEquine

Reduce heat stress: During hot weather keep your horse out of the sun; provide an evaporative cooler, air conditioner or fan. Frequent sponge baths with cool water during excessively hot weather, paying special attention to the neck and inside of rear legs. Consider moving the horse to a cooler climate.
Activity: If exercise is necessary do so during the cooler part of the day, early morning. Hose off the horse after exercise to adequately cool him. Schedule intensive training during the cooler months so the horse is fit and not over weight during the summer.
Diet: Affected horses are often mildly anorexic. Normal diet can be maintained but decreasegrain and other concentrates. Provide salt block. Provide lite salt (electrolytes) at a rate of 4 ounces per day. Avoid obesity. Provide a ready source of cool fresh water at all times.
Turnout: turn the horse out during the coolest part of the day (early morning). Provide shade. Don’t leave the horse out without shade during the hot part of the day.

Your horse may regain the ability to sweat during the cooler months only to have the conditio return during the summer months.
Your horse will be prone to poor performance during the period that he/she cannot sweat normally. Dangerous over heating and heat stroke can occur if the horse is exercised during the hotter periods of the day. Heat stroke can also occur if environmental heat stress is not controlled.
This condition is usually a lifelong problem, but it has been reported in a small number of cases that some horses recover and do not have a return of symptoms.
Most affected horses respond to a change in environment, i.e. a cooler climate and begin to sweat normally after a few weeks but the symptoms usually reoccur when exposed to a hot climate.

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