Spaying a mare (ovariectomy) means removing her ovaries so she no longer comes into heat and has a more mellow attitude, like a gelding. An ovariectomy can be done standing (under sedation and local anesthesia) through a flank approach or a vaginal approach.

An infrequent complication associated with the old method of spaying (using a very old surgical instrument, a chain escraseur) is bleeding from the ovarian stump or uterine artery. The escraseur looks like a bicycle chain on a long-handled clamp. The crushing technique is similar to that of an emasculator when gelding a stallion; crushing the blood vessels causes them to spasm and close down, with less bleeding than if they were cut, but this procedure is very painful. Many vets now use laparoscopy for spaying. With a laparoscope, they can see exactly what they are doing while removing an ovary, and they can either ligate (tie off) the ovarian pedicle (stump), or apply a stapling device to control any hemorrhage.

Some vets are now tying off the blood supply to the ovary (controlled ovarian infarction) rather than severing its attachments, which is less risky. (Similar techniques are used in small animals to remove organ function.) This has also proven to be more comfortable for the mare. In a study done at the University of California, Davis, in 1999-2000 by Tom Yarbrough, DVM, and Chris Hanson, DVM, on eight mares, it was found that ovaries degenerated and became non-functional after the blood supply was tied off. There was no evidence of infection, pain, revascularization (re-establishment of blood supply), or adhesions following the procedure, and the mares’ hormone levels no longer fluctuated.

Hanson moved to private practice in Washington, and Yarbrough continued work at UC Davis and did surgeries at private clinics. Both began doing all their laparoscopic spaying cases using this method. “During the past three years, we have each done about three dozen, and this has so far shown to be a safe technique,” said Yarbrough