Behavior Modification in Horses
Part 1

Dr Lisa Grim
copyright Equitage Horsecare
January 11, 2012


Horses have been ridden by humans for centuries.  Over time they have become domesticated and people have learned many useful training techniques to create riding companions and sport horses.  As horse people we all enjoy the unique relationship we have with our horses and the elegant teamwork in an event after hours of practice and training.  Occasionally we find that our horse may change their behavior suddenly and be reticent to the previous training protocol or irritable and non-responsive to aids during a competition.  So, where do we begin?  Is this a training issue, a behavior issue or a pain issue?  If this is a sudden change in behavior in a horse who has been previously well trained and cooperative, a full evaluation of the horse’s health and environment is helpful.

Some of the common areas to evaluate when we see a change in behavior are:
1.Hormonal  Part 1
2.Environmental (change in location or neighbors)
3.Musculoskeletal Pain (arthritis)
4.Internal pain (colic, ulcers)
5.Mental?

Since this is an extensive list I am going to talk about the first factor today and continue on in another post to follow.

Hormonal behavioral changes
The most common hormonal behavioral change we hear about is with mares that come into “season”.  Mares cycle about every 21 days.  On average they are “in” their estrus for 5 days and then calmer and “out” for 16 days.  Of course this timing can vary.  Some of the common behaviors in strongly affected mares include: irritability, kicking at other horses, swishing the tail, squatting, “winking” and urinating frequently, squealing when male horses are around, a non-cooperative attitude and unwillingness to move forward.  I have seen extreme cases where mares actually seem painful during ovulation and may lean on fences, damage horse trailers or have colic symptoms.  Less obvious symptoms may just be a decreased sensitivity to aids, unwillingness to move forward and/or general malaise.  Other symptoms of course are possible and any change in behavior that seems to follow the 5/16day rule is probably related to estrus.

Treatments for mare estrus behavior changes
1.Hormonal treatments

a.Oral Altrenogest (Regumate). This is an oral progestin that is administered daily.  Some mares do very well on this product and it is the only hormone treatment that has been experimentally proven to decrease cycling and ovulation in the mare.  The down side to this product is that it needs to be given every day during the time period you want to suppress estrus.  Also the oral liquid can be challenging to give and tends to easily drip on the person administering the product.  Gloves should be worn and hands washed to prevent absorption through the skin.

b.MedroxyProgesterone injection:
This product in injected every 3-4 weeks and basically suppresses the behavior during one estrus cycle.  The advantage is that it is only one injection every 3-4 weeks.  The down side is that it has not been proven to suppress ovulation and it doesn’t work in about 20% of mares. If given by the owner the cost is reduced from Regumate.

c.Repository Progesterone Implant (Synovex):
This is an implant that is surgically placed under the skin of the mare about every 3 months.  This works very well for about 80% of the mares it is tried on.  Advantages are that it is only once every 3 months, can be planned ahead for the show season and is the cheapest cost per day of the hormones.  Disadvantages are that the beads do not always dissolve and sometimes can be seen and felt.  Swelling can occur at the site of injection.

2.Natural Treatments

a.Herbs and vitamins:
There are many natural products on the market for oral supplementation.  Raspberry leaves have been used for centuries to decrease estrus symptoms.  Other supplements may concentrate on calming the horse with B vitamins, Magnesium and Tryptophan. As with all medications and herbs the affect can vary widely with the individual horse, but I believe they are worth trying.

b.Acupuncture :
Horses have been treated with acupuncture for over 3000 years.  Many behavioral issues including hormonal imbalance can successfully be treated with acupuncture.  Preferably at least three treatments are performed and usually we can keep the mare balanced for the year.  This is definitely worthwhile for any mare and especially those who have not responded well to hormone therapy or the owner would like to try a more natural approach



Other hormonal behavior changes
1.Aggressive stallion like behavior in a mare:
If a mare tends to exhibit more and more aggressive stallion like behavior there may be a problem.  There is a tumor of the ovaries that is called a granulose cell tumor.  Usually that ovary is much enlarged and tends to secrete extra testosterone, hence the stallion like behavior.  Diagnosis of the condition includes palpation of the ovaries, ultrasonography of the reproductive tract and a blood hormone profile.  If the hormones follow a specific pattern it is usually easy to diagnose a granulose cell tumor.  These are treated by surgical removal of the affected ovary.  This procedure can be done standing with few complications.

2.Hormonal behavioral changes in a gelding
So your gelding is acting a lot more like a stallion. more energy and aggressive behavior.  It is usually a good idea to do a hormone profile.  On rare occasions the horse can actually be a cryptorchid which is a male horse is an undescended testicle.  These horses tend to be exceptionally aggressive and should be diagnosed and treated post haste.  The treatment is to remove the retained testicle.  Sometimes this can be found to the exterior of the abdominal wall which would be a simple procedure.  If the testicle cannot be found, it is most likely in the abdomen which must be opened up to find and remove the testicle.

3.Unusual behavior in senior horses (Cushing’s Disease)
As our horses age they can develop many new conditions that may affect their behavior.  They can have kidney or live dysfunction which will be covered more in the internal organ section.  They can also develop Cushing’s disease which is better known for other symptoms such as laminitis.  However this is a tumor in the pituitary.  Depending upon all the chemicals it stimulates the body to secrete and the space occupying area in the brain, there can be behavioral changes with this disease.  Some of the symptoms I have observed include falling asleep while standing, unsteady with the Farrier, anxiousness and a general picky appetite.  This can be easily diagnosed with a blood test and is treated with a once daily dose of Pergolide.



Continued in Part 2

Equitage Horscare
Lisa A Grim, DVM
P. O. Box 8092
Rancho Santa Fe, CA 92067
760-634-2144
office@equitage.com