Heaves

With winter right around the corner here in North Carolina, it’s important to discuss the condition known as heaves, which affects heaves prone horses being stalled.  Heaves is an allergic, inflammatory, and obstructive airway disease affecting older horses and similar to asthma in humans.  The technical name for heaves is actually Recurrent Airway Obstruction.

Heaves is more common in horses who are stalled and fed hay.  It may be initiated by the inhalation of organic dusts, such as those associated with hay and bedding materials. These organic dusts contain allergens, endotoxins, molds, and other small particles which can initiate the inflammation process of the lungs.  There appears to be a genetic predisposition to heaves since not all horses develop the condition who are stalled and fed hay.  Even good quality hay can initiate an episode in a heaves prone horse, but it should not be of danger to a horse without the condition.

When heaves predisposed horses are moved from the pasture to a stall and fed hay airway inflammation can occur within six to eight hours.  Airway obstruction happens as a result of bronchospasm, mucus accumulation, and airway wall thickening.  Heaves affected horses have their airways narrow in response to allergens, dust, irritant odors, etc. and this condition is known as hyperresponsiveness.  For heaves affected horses, even a brief exposure to the stable environment can induce hyperresponsiveness.

In severe cases, affected horses have marked respiratory distress, the horse is typically seven years of age or older, and has spent a large portion of its life being stalled.  During a severe acute episode, their nostrils are flared, respiratory rate is increased, the horse is anxious/agitated, they can have a nasal discharge, and use their abdominal muscles which can lead to the development of “heave lines”.  During mild cases, horses may cough during exercise, feeding, cleaning the barn, and may have reduced exercise tolerance.  Your veterinarian is the person who can make a definitive diagnosis of heaves.

There are a few ways to manage heaves such as changing your horse’s environment, changing your horse’s diet, or your veterinarian can prescribe medications.  When changing your horse’s environment, moving your horse to pasture is the best option, however, it should not be a dry lot.  If that is not possible, then you should improve your barn’s ventilation and move your horse to a part of the barn where airborne particles are fewer.  Avoid storing hay in the loft, sweeping constantly, and you should change your horse’s bedding to one that produces less dust such as chopped paper or cardboard.  Your horse’s diet should also be changed to one that contains less dust.  In the winter when grass is low, pelleted feed should be provided and rolled grains should be avoided due to their high dust content.  Round bale hay should be avoided because horses will eat the center out of the bale, therefore inhaling even more particles.  If it is not possible to cut hay from your horse’s diet, then it should be soaked in water for five minutes before it is fed.  Also, alfalfa pellets and alfalfa cubes have a low amount of dust.  Finally, medications may be prescribed by your veterinarian, but this is something a veterinarian must recommend.

 

For more information, please contact your Livestock Extension Agent and review the following Extension publication:

http://www2.ca.uky.edu/agc/pubs/asc/asc172/asc172.pdf

This article was adapted from a University of Kentucky Cooperative Extension Publication, ASC-172, written by Dr. Fernanda Camargo, Dr. Bob Coleman, Dr. Laurie Lawrence, Dr. Mary Rossano, and Kristen Harvey.