12-05-2011, 06:45 PM
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'Heave Line' is created by the abdominal musculature, however it is not the only thing seen in a 'heaves/heavy' horse. A horse with heaves or COPD/RAO essentially has allergic reactions to mold/dust in hay/barns/etc. They usually have a few common clinical signs: cough a few times when warming up during riding which stops after they are a little warmed up, a clear or slightly opaque nasal discharge at the onset of coughing or while eating, they may cough while eating hay - especially dusty or moldy hay, and they have a 'heave-line'. The 'heave-line' is important to differentiate from normal hard breathing - it is actually a double expiration. Basically, they exhale a normal amount (showing the line especially when out of shape) and then they have another short exhale after that to expel the extra air in their lungs which cannot escape as in a normal horse because of the smaller/inflammed airways. If you carefully observe your horse, you will be able to differentiate an out-of-shape horse from a horse with 'heaves'.