In this episode of the Disease Du Jour podcast, Rebecca McOnie, DVM, DACVS, discussed equine castrations, including her preferred surgical techniques, anesthesia recommendations, safety considerations, and more.
This episode of Disease Du Jour is brought to you by Equithrive.
Presurgical Examination
McOnie’s preoperative exam involves checking the horse’s temperature and ensuring the horse doesn’t have a recent history of diarrhea, coughing, or airway problems. She performs bloodwork to check hydration and red blood cell density and confirms the horse has an up-to-date tetanus vaccination.
McOnie also performs a full physical examination of the horse’s scrotum and testicles before operating. “We want to make sure that both testicles are in fact descended in the scrotum and that they palpate normally, that we’re not finding any additional tissue, for example, intestines sitting within the scrotum,” she said. For cryptorchids, McOnie tries to determine whether the second testicle is inguinally or abdominally retained, which can provide a better idea of how to proceed surgically.
Ideal Age to Castrate
“Most of the time, we’re aiming to castrate horses between about six months and two years of age,” said McOnie, explaining that young horses are better candidates for anesthetic procedures due to their smaller size.
“In older horses, the major differences that I’ve encountered as far as castration are the extent of the blood supply associated with the testicles, which is pretty immense in older stallions, and their potential for having a little bit more pain following castration,” McOnie said. She explained that in older stallions, she generally prefers to perform a controlled primary closure castration in an operating room.
Anesthesia and Safety Protocols
McOnie primarily works in a hospital setting, where she typically runs foals on triple drip with oxygen supplementation. In general, however, she said a standard dosing of xylazine and diazepam followed by ketamine is a “pretty safe bet.” She recommended having top-ups available for spunky horses and potentially having a temporary catheter in place to maintain anesthesia.
McOnie also emphasized the importance of working in a safe environment. For older stallions, she recommends castrating in lateral with the leg elevated, which practitioners can accomplish by tying the leg forward around the neck and chest (with a quick-release knot). She said smaller weanlings can be in dorsal and steadied with shavings or straw bales to keep them positioned.
Potential Complications
McOnie said complications following castration are relatively low in occurrence. “That being said, we don’t want to underestimate the potential for complications,” she said.
The most common complication McOnie sees is surgical site swelling. “So, making sure that we adequately manage bleeding and ensure appropriate hemostasis during surgery is very important,” she said. She noted it’s important to allow adequate drainage when using an approach that leaves the skin open.
A more serious complication is testicular artery hemorrhage, when the cord and testicular artery rapidly retract into the inguinal canal or abdomen, which can cause substantial bleeding. “That can be really difficult to manage in the field, and we have a really nice technique to manage that at a referral institute,” McOnie said.
Infection is another potential complication, especially in field procedures where the environment is less controlled.
In the episode, McOnie discussed equine castrations in detail and described her preferred surgical techniques.
About Dr. Rebecca McOnie
Rebecca McOnie, DVM, DACVS, is an assistant professor at Cornell University’s College of Veterinary Medicine. She earned her Doctor of Veterinary Medicine degree from the Western College of Veterinary Medicine in Saskatoon, Saskatchewan. After four years on the Canadian Prairies, she spent a year as a rotating equine intern at Arizona Equine, outside of Phoenix. She then moved to upstate New York, where she completed a three-year residency in large animal surgery at Cornell University. Her areas of interest are equine sports medicine and surgery, as well as large animal emergency and critical care.
Related Reading
- Tips on Performing Equine Castrations
- Equine Pain Assessment Tools and Techniques
- Research on Equine Cryptorchid Testes Removal
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