I mention Gracie in my "About" page - she's the horse that inspired me to study equine behavior more in-depth. Here is a more detailed description of the behavior problems we encountered and then resolved using proven training methods.
Estimated 15-year old mare rescued from situation in which she was kept in a small paddock with two intact stallions. She was denied food (severely emaciated) and sustained permanent injuries to her withers from repeated mounting by stallions. Subsequent surgeries were required to remove infected tissue and fractured pieces of bone in the injured area. Upon physical rehabilitation at the rescue, Gracie displayed bite threats to human handlers upon their approach and/or physical contact, especially in the area of the injury (the withers). Negative association with touch in the area of injury in conjunction with the presence of humans was obvious and an approach of gradual desensitization to touch and human proximity was used in order to eliminate the biting behavior. The biting behavior was successfully reduced within 6 months and eliminated completely within 2 years.
Gracie displayed biting threats upon approach by humans and the threats increased in severity with proximity and physical contact to injured area.
A gradual method of desensitization was used to earn trust. For the first few days of interaction, I sat quietly at a distance of at least 10 feet (which is about twice the natural space barrier preferred by horses). The space between us was gradually reduced over several days until I could stand next to her without her moving away or displaying bite threats. This method continued on to touching: if I tried to place a hand on Gracie's shoulder and she threatened to bite, I pulled away and stepped back to decrease the tension. Desensitization continued with gentle brushing of her neck and back, avoiding the withers, and then eventually extremely gentle brushing of the withers. The latter part of the process took a matter of several months. Within two years it was possible to physically clean the withers and apply light hand pressure without adverse reaction.
This example demonstrates that trauma responses in horses can be reduced or eliminated over a matter of time using gradual desensitization. Care must be taken to ensure that the horse is never re-traumatized, so the process must be as gradual as the horse's comfort level dictates - whether it takes a matter of days, months or even years.