The main triggers that can initiate over breathing are
- emotional stress
- physiological stress
- over eating rich food
- toxic stress
- over heating
Horses are flight animals that are evolved to live in the constant social interaction of herd life. Shutting horses in stables on their own denies these basic instincts and can cause emotional stress.
Despite centuries of domestication horses retain the physiology and anatomy of flight animals. They have evolved to be constantly on the move, covering large distances and eating lightly most of the time. These lifestyle elements are essential for complete health.
However many horses these days are kept inactive and fed high energy low fibre food which is alien to a horse's natural diet and periods of hunger can occur between meals.
Horses may have their temperature regulatory system undermined by the use of artificial clothing and therefore overheat and chill at times.
Illness or injury can trigger over breathing.
Horses it seems, like humans tend to co-ordinate their breathing to the pattern of the worst, breather. A newly weaned youngster that is over breathing is likely to have a bad effect on the breathing of new stable or field mates.
Horses also seem to copy over breathing by humans. So over breathing whilst handling horses is likely to have a detrimental effect on the horses' breathing pattern. These days most people over breathe for many of the same reasons that horses do. The deterioration of human breathing over the last century has been charted in various research papers cited in Artour Rakhimov's book, Normal Breathing .
Any chemicals that are not useful to the horse's body have to be detoxified and eliminated (or stored). Today's horses have to deal with wormers, veterinary drugs and treatments, fly sprays, food supplements, food additives and traces of pesticides in food or in spray drift.