Below is a link to an article on a study done in France on pain related behaviors in horses.
Also pain issues I have found will change herd dynamics as well. A horse in pain will often act as the herd dominate and/or stay farther distanced from the core group in trying not to move or be moved by the other horses in turn being aggressive . When the pain is reduced or removed they can change from being an aggressor in the herd dynamics.
Liz
