Horses also may make a noise when breathing. The bouts may be mild and infrequent or may not even be noticed. On the other hand, they may be frequent, severe, and long-lasting. Most horses recover after a 15-60 minute bout. Most bouts occur at rest and are triggered by stress, such as transportation, illness, even feed changes or increased potassium in the blood.
HYPP horses have a defective sodium ion channel in the muscle cell membrane.
The normal flow of sodium ions in and out of the muscle cell is disrupted, resulting in muscle tremors. But, some foals show signs also. HYPP horses require special management. Keep them in large pastures rather than stalls. Feed small amounts, two, three, or more times daily and exercise them regularly.