Yawning in Horses

Yawning horse: Permission given for image use by my dear friend, Frank.

We have all seen our horses yawn. Why does a horse yawn? That is a good question. In fact, it is not really known why horse yawn. Some suggestions for this behavior are the following:

• Change of sleeping, napping and waking state.
• Physical fatigue
• Mental stress
• Release of mental or physical stress. Horses will often yawn after a chiropractor session or massage session. They will also pass gas!
• An attempt to clear airways or equalize pressure in the ears.
• Extending jaw muscles
• Pain (colic, ulcers, trimengial nerve pain in the face, teeth, gums, etc.)

*The trigeminal nerve is responsible for sensation in the face. Sensory information from the face and body is processed by parallel pathways in the central nervous system.

The trigeminal nerve distribution in the horse's head. The three branches of the trigeminal are shown (ophthalmic (1 st), maxillary (2 nd) and mandibular (3 rd)). Adapted from Goody, P (2000) Horse anatomy: a pictorial approach to equine structure 2 nd Ed. J.A. Allen Publishers, London. From Taylor, K. (2004) PhD Thesis, De Montfort University, Leicester.

• Neurological problem
• Liver disease
• Parasites - My husband's horse has neck threadworms that have travelled to the eyes. This horse sometimes yawns more often when the parasites are active in the spring. We have no Equine Parasites scientific proof, but this has been our observation.
• Clogged tear ducts
• Boredom
• Habit
• Distress or fright
• Anticipation of feeding time
• Eating stemmy hay or soaked pellets seems to cause some horses to yawn.

"About the only thing we're fairly sure of is that the trigger is not the same as that of a yawn in humans, which is in response to transient drops in blood oxygen levels. That big intake of fresh air increases oxygen in the lungs and therefore in the vascular system. However, horses do not appear to be inhaling when they 'yawn.'" What Makes a Horse Yawn? - by: Mary DeLorey, DVM

The only certainty is that horses do yawn!