Anhidrosis can spell BIG trouble!

When exercising, the horse’s working muscles generate heat… The body heats up… The horse sweats… Excess heat is then dissipated through evaporative cooling. As simple as that! Right? Unfortunately, this isn’t the case for all horses.

Picture this – it’s a typical Summer’s day in Australia. Hot. Humid. Plagues of flies and other bugs. Cicadas playing their deafening melody. Of course, it’s a great day for a ride! So you set out on a trail ride with your friends. After a brisk trot and canter, you, your friends and their horses are drenched in sweat, but your own horse is dry as a bone.

Anhidrosis is a condition where horses lose the ability to sweat. The condition can affect any horse, but appears to be more prevalent in hot, humid climates. Not all anhidrotic horses completely lose the ability to sweat. Some will have decreased sweat production and others will only stop sweating in certain areas. As you can imagine, this poses a significant problem for regulation of body temperature (thermoregulation), especially when exercising. However, anhidrosis is not only an issue for those in work, but horses also rely on sweat to help keep them cool during hot weather and periods of stress, such as a floating trip.

Anhidrosis is not well understood and there are various factors such as environment and potentially genetics that play a role in the condition. As a horse owner, the best thing you can do is be aware of the clinical signs and management practices to help reduce the risk of heat stress.

Clinical Signs:

  • Dry coat after work in warm weather (ranging from completely dry to damp patches under tack or between the hind legs).
  • Laboured breathing – Respiratory rate may be increased (rapid, shallow breaths) even though the horse hasn’t worked very hard. This is because the horse is trying to lose excess heat from the lungs.
  • Hyperthermia (increased body temperature).
  • Poor performance – the horse may be lethargic and unwilling to work.
  • Chronic cases may develop a sparse coat with scaling, particularly around the face, neck and shoulders.

Management Practices:

  • Exercise the horse during the cooler parts of the day (early morning and late evening).
  • Implement a rigorous cooling down procedure – continually cold hose your horse until cool. Use fans if they are available to you. Continue until the horse’s body temperature and other vital signs have returned to normal.
  • Ensure the horse has adequate shelter in the paddock.
  • If they are stabled it must be well-ventilated and use fans to help maintain air flow.
  • Ensure the horse has constant access to cool, fresh water.
  • Electrolyte supplementation can trigger a return to normal sweating in some cases.
  • Depending on the severity of the case and where the horse is located, it may be advised to move the horse to a cooler climate.