Although considered a routine procedure, castrating stallions has its complications. During a Burst presentation at the 2024 AAEP Convention, Holly Stewart, VMD, PhD, Dipl. ACVS (LA), assistant professor of large animal surgery at Penn Vet’s New Bolton Center, shared what she has learned about making castration procedures run as smoothly as possible.
Before Getting Started
“First, confirm you have two testicles before you get started,” she said. “Make sure what you’re feeling isn’t a slip of fat.”
Do not proceed if the horse has only one testicle or if you observe abnormalities with one or both testicles. Additionally, Stewart recommended proceeding cautiously if testicles seem abnormally large, since they might require more extensive ligation or have a greater risk for bleeding.
Before getting started, be certain you’re organized. Stewart suggested using a tote designed just for castrations with enough supplies for two castrations (even if you’re only performing one).
Anesthesia for Equine Castrations
For anesthesia, an intravenous catheter is very helpful, especially if you are working alone. Sedating with detomidine can be better for recovery compared to xylazine. Acepromazine is not recommended for castrations.
“You can induce with ketamine alone, but you will have better relaxation if you can use both ketamine and midazolam or diazepam,” Stewart said.
Castration Procedure
With the horse on his back, remove the more challenging testicle first, which might be the smaller testicle or the one that is more difficult to grab. If the horse is in lateral, start with the one closest to the ground.
Don’t become complacent with your emasculator.
“It happens all the time that we miss the ‘nut to nut,’ orientation of the emasculators,” said Stewart.
Closed castrations (where the vaginal tunic around the testicle remains closed) are ideal. Veterinarians should stretch the skin after removing both testicles to decrease any active bleeding and encourage drainage after recovery to reduce swelling. You can minimize long-term complications such as scirrhous cord and hydrocele by ensuring adequate drainage post-procedure.
Complications
“The No. 1 complication following castration is swelling, not evisceration or hemorrhage,” Stewart said. “Discuss what to expect regarding swelling with owners before leaving the farm, including when to call.”
In the rare case the horse eviscerates, re-anesthetize him (remember you have an IV catheter), clean off any obvious debris, reduce the intestines into the scrotal skin only, suture the skin, and refer immediately. Evisceration is not a game-ender, said Stewart.
Finally, don’t forget the tetanus vaccine!
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