The Collaborative International Dictionary of English v.0.48:

Heaves \Heaves\, n.
   A disease of horses, characterized by difficult breathing,
   with heaving of the flank, wheezing, flatulency, and a
   peculiar cough; broken wind.
   [1913 Webster]

WordNet (r) 3.0 (2006):

heaves
    n 1: a chronic emphysema of the horse that causes difficult
         expiration and heaving of the flanks [syn: heaves,
         broken wind]