The Spayed Mare

     Some breed registries allow a tentative registered mare to move up to permanent registration when she is spayed.

     If a mare has developed dangerous behavior as a result of hormone imbalances resulting from  an ovarian tumor, removing the ovaries can redeem the mare's chance at a useful non-breeding role.  Mares with granulosa tumors most often display wicked habits such as squealing, biting kicking and exhibiting stallion-like behavior.  In 90-95% of the cases, surgical removal of the tumor and/or ovaries eliminates the undesireable behavior. Mares that have developed cresty necks and voice changes most often retain the characteristics after surgery.

     Less dangerous mares, but those with  irritable, fussy or silly periods every month may be regarded as a nuisance in terms of show, race or ranch work.  If a mare is valued,  but not for breeding purposes, spaying may provide the necessary alternative to produce a more solid performer.

     A non-surgical treatment for mares with undesirable estral behavior is the administration of an oral synthetic progesterone, Regumate.  Progesterone is the calming female hormone responsible for maintenance of pregnancy.  Regumate's inhibiting effect on the occurrence of the estrous cycle might provide  temporary help during a prospective broodmare's show or race career.

     If more permanent measures are required, the mare owner must look to surgical alteration.  Dr. Robert K. Shideler of Colorado State University's Veterinary Teaching Hospital outlined three methods of removing the ovaries.

     Major abdominal surgery under general anesthesia is the most expensive method involving the longest recovery period, yet may be the only option available to horse owners in many locations.  The ventral midline incision made from the umbilicus toward the udder gives the practitioner easy access to the ovaries.  The surgeon has absolute hemorrhage control which is essential when dealing with the highly vascular ovary with a tumor.  Major vessels are tied.

     The patient usually remains in the hospital for observation for 10-12 days, then is restricted to box-stall/paddock confinement for an additional 30 days.  It is usually 90 days from the date of surgery until the mare can return to training.  As with all major abdominal surgeries, there is the risk of anesthesia and post-operative complications such as colic.

     The flank approach is usually performed with the horse standing in stocks, under the influence of a tranquilizer and local anesthetic.  Often a four inch incision is made in both flanks to allow the surgeon easier access to each ovary.  Removal can be made with an emasculator, such as used in the gelding process or with a chain loop ecraseur.

     Recovery is quicker than with abdominal surgery. Beginning with one day for observation in the hospital, the horse should spend  10-14 days in stall/paddock confinement and a return to work 30 days from the date of surgery.  Generally the flank method provides few complications but does yield minor scars.

     The vaginal approach is the fastest, most inexpensive method, costing about 1/4 that of abdominal surgery.   However, the vaginal approach requires a higher level of technical experience and may not have widespread availability.  Mares must be free from reproductive tract infection and are routinely put on antibiotics before and after surgery.

     It is especially important when choosing this method to fast the mare for 24-36 hours prior to surgery  to ensure minimal intestinal fill.  The mare is restrained in stocks, under the influence of a tranquilizer and local anesthetic.  The surgeon makes entry through the vulva and a small  incision is made in the vagina.  The ovaries are severed from their attachments by  utilizing a chain loop eraseur.   No ligation of vessels is required and no vaginal sutures are necessary.  There is little trauma and jeopardy involved in the vaginal approach.

     After surgery, the mare is usually kept standing in crossties for 24-48 hours because laying down might allow protrusion of intestine through the incision.   During this time she should be periodically hand-walked for exercise.  After 3-4 days in a box stall, she can be turned into a paddock for a week, and then returned to work.

     When to spay a mare depends somewhat on the reason for the surgery and the subsequent method of choice.   Abdominal surgery would be necessary for the mare with a large ovarian tumor and could be performed at any age.  It would also be appropriate for routine ovariectomy of the yearling as the longer recovery time would not interfere with a performance schedule.   From a technical standpoint, both the vaginal and flank methods are best suited for a mare 2-3 years of age whose mature proportions allow the surgeon room to operate.

     Spayed mares no longer have estrous cycles, so do not exhibit estrous behavior.  Otherwise, there are no behavioral changes associated with an ovariectomy.  Likewise, other than the absence of ovaries and the decrease in estrogen production, there are no physical changes.  The mare's metabolism does not slow down; she does not become an easier keeper; she does not gain weight more readily unless the hand that feeds is too generous.

     Spayed mares do not lose their feminine features.    Your mare will look as sweet as she did before surgery.  More important, she will behave more consistently.

     Removing a mare's ovaries is a permanent way of altering her estrous cycle and behavior.  After careful consideration of breeding potential and intended use, spaying may be the answer to one of your mare management questions.