When pain leads to aggression, it can mean bad news for everyone involved. EW seeks the advice of an expert in order to shed some light on pain-related behavioral issues.
Q.  I have a ten-year old paint I purchased eight years ago. I found out through several sources that his prior trainer abused him severely.

After a lot of patience and TLC he began to mentally get over what happened. He has thrown me a couple of times. There was always an outside reason as to why. Recently, while he threw a horrible bucking episode, I found out his back was injured, more than likely from the abuse. This was then confirmed through my vet who is also an equine chiropractor. She told me that evidence shows that my horse has been flipped by the trainer and had fractured his growth plate. We then proceeded with some chiropractic work and pain meds. Within a few months my vet gave me the okay to work him and ride him with a cut back pad to keep weight off his withers.

My horse, Hotrod, throughout the entire eight years that I’ve owned him, never once showed any kind of aggression, even when he was in pain. As soon as he was out of pain, he turned aggressive. He tried to bite me. He lunged with his ears pinned back. He reared at me. He did this to everyone. Even when any of us tried to go to the pasture to get another horse, he would come at us with his ears pinned. I didn’t want my daughter to even go into the pasture for her pony for fear of what he might try to do.

The vet then tested him for Lyme disease, as that tends to cause aggression. We also tested for Insulin Resistance. Both tests came back negative. I can’t afford to do blood tests after blood test until we figure out what it is. I’m aware that it could be behavioral. It just seems odd that something behavioral could happen so suddenly. I’m wondering if you have any ideas what else it might be? He seems somewhat better at times, but I still see the aggression wanting to rear its ugly head.

Thank you for your time. I would appreciate any help or ideas that anybody may have.


A.  This horse sounds like quite a project and you have done a lot to help him out. There can be many reasons for this behavior, and from a distance, I can only give some suggestions.

Horses who have been abused often shut down mentally in order to protect themselves from pain and torture. In some cases, once the pain is gone, the real personality comes out. However, it does not usually show up in such a negative way. Most commonly, horses that appear quiet or withdrawn come out of their shell and can be quite active and sometimes hard to handle due to excessive energy or personality. I do not think this is the case with your horse.

I am glad you took a Lyme Titer to check for the disease. Unfortunately the test we have (and all the more sophisticated human tests) are not all accurate. I have had many cases with negative tests, but their symptoms looked like Lyme and nothing else. These I have treated with antibiotics (and immune system support that I use) and have had very good results. There are also tick borne diseases that we have not identified yet (this statement was made by some human infectious disease doctors). There are also newly identified tick diseases in human medicine for which we have no equine tests. (See my facebook pages for posts on any new tick diseases, I have posted several already in the last year).

I personally would keep Lyme or a related disease on my list. And although I approach medicine from a holistic perspective, it might be worth doing the 30 days of Doxycycline treatment. I would also get with a homeopathic veterinarian ( and to help with the treatment from a holistic perspective.

I have seen horses that have been in pain for many years change in a negative way after they get treated. This usually occurs when a horse becomes pain free, then experiences a slight return of symptoms (it is not possible to cure everything in a severely abused horse in a few treatments, even if they seem much better). It seems that these individuals become over reactive to their pain. Because this behavior is so strong in the paddock and not related to riding, this is not high on my list of possibilities.

Behavior issues can come from unusual places. I have had a few cases of aggression that were directly related to a rabies vaccination. When we treated the horse homeopathically for that, the behavior change was good. To approach the horse from this perspective takes an experienced and well-trained veterinarian. There are also unusual cases, such as a brain tumor, EPM that has migrated to the brain, and headache pain from many sources (some drugs such as pergolide can give headaches as a side effect). Since headaches are very difficult to recognize in horses, most people do not consider it as a possibility.

As part of the healing and rehab process, it may be worthwhile to find a professional to help out. Be careful if you send him to a professional trainer–look for one that understands difficult horses, and remains kind during the training process.

I would try to pursue some form of alternative treatment to ease his aggression and not give up, if possible. But do keep yourself and your family safe, one’s life or limb is worth more than the horse.

Dr. Joyce Harman is a veterinarian specializing in acupuncture, chiropractic therapy, and a variety of holistic methods. She has “written the book” on saddle fitting, with two volumes, The Horse’s Pain Free Back and Saddle Fit Book for western and English horses. She also has a booklet to help introduce people to homeopathy for horses, The First Aid Guide to Homeopathy for Horses. Her goal is to help educate the equine industry about natural, holistic and integrative medicine. Got a question for Dr. Harman? Just leave us a comment on our Equine Wellness Facebook Page. She will be answering 1-2 questions every week!