My friend's TB mare has a head shaking issue. She dose it CONSTANTLY. Lol her neck is as hard as a rock XD. She dose it more when she is 'stressed' (or is unhappy about something and is having a 'moment') I have some vid, not the best angle though.
When she shakes her head she tightens her lips too.
I was wondering if anyone has seen this before and can give me more information. All I can find is allergies but she dose this all year round.