Q: I have considered neutering my 8-year-old Quarter Horse mare but would like more information on this topic. What are the different procedures used to neuter mares? Has a study been conducted on changes in mares after neutering? Does the neutering help create a more calm or steady horse (like the difference between a stallion and a gelding)? Does age affect this outcome? Would buyers discount a neutered mare, or would she be considered the same as a gelding in desirability? Christine Barsema; Clearwater, Florida

A: Ovariectomies—removing the ovaries of (neutering) a mare—can be done by several methods, each with pros and cons. Weighing the differences in cost, recovery time and incisional healing will help you decide which procedure is best for you and your mare.

Laparoscopic surgery is a technique used to gain access to the inside of the abdomen by inserting tools, including a light source and camera that sends images from inside the cavity to a monitor, through several small incisions. Because the incisions are small, the horse’s discomfort as well as hospitalization and recovery time are reduced. In most cases this procedure is done in standing sedated horses. In addition, the cosmetic outcome is usually outstanding. Unfortunately, the advanced equipment needed to perform the surgery is often available only at universities and specialty hospitals.

A colpotomy, removing the ovaries through a hole in the vagina, requires less equipment and fewer personnel, so the costs of this procedure are low. However, it also poses more risks to the mare. Complications may include delayed healing of the vaginal incision, development of abscesses or hematomas and/or adhesions of abdominal organs to the incision.

Another route to consider is an open-surgery procedure, in which the ovaries are removed through an incision in the abdominal wall large enough to admit the surgeon’s hands. These procedures allow the maximum amount of room for ovaries to be removed, which is important if ovarian size cannot be determined in advance. However, open surgeries require general anesthesia, provide the least cosmetic results and vary widely in cost. The potential complications are similar to those of a colpotomy.

Studies have been done on how ovariectomies change behavior. Overall, mares do seem to have reduced aggressiveness, excitability, kicking and biting. We tend to see better results, particularly with behavior issues, if the procedure is done before the mare is 10 years old.

Buyers are becoming more receptive to neutered mares and consider them to be similar to geldings. However, to be honest, most people who liked their mares well enough to pay for the surgery do not consider selling them later.

Dean Hendrickson, DVM, MS
Colorado State University Veterinary Teaching Hospital
Fort Collins, Colorado