Simply due to the nature of the procedure—removing a horse’s testes—castration can lead to major blood loss from the testicular arteries if its not stopped in a process called hemostasis. While many veterinarians use a clamp to accomplish hemostasis, a Swiss research team has uncovered significant benefits to a different castration and clamping method—one that involves using a power drill.

“The ‘twisting’ seems to improve hemostasis, and it also has the advantages of getting the job done quickly and keeping the surgeons’ head and upper body out of the ‘danger zone,’ where they could get kicked (in a standing, sedated horse),” said Christoph Koch, DrMedVet, Dipl. ACVS, ECVS, of the University of Bern Vetsuisse Faculty Swiss Institute for Equine Medicine.

He said the power drill method—called the Henderson technique—is easy to perform and well tolerated by the horse. And, when it’s combined with a “closed” castration, complication rates are particularly low compared to other techniques, he added.

Open and closed castrations refer to what surgeons do with the internal sac that houses the testes, called the parietal tunic. In an open castration, the surgeon opens this tunic to remove the testes and access the testicular artery to clamp it shut. In a closed castration, the surgeon removes the tunic with the testes still inside it. Then, using the power drill and a specialized attachment, the surgeon stops the arterial blood flow by adding a clamp over the arteries within the tunic and twisting it at high speeds.

In their study, Koch and colleagues followed 300 equids (269 horses, 23 ponies, and eight donkeys) castrated standing and sedated using a closed technique and the Henderson equine castration instrument. Post-surgical infections occurred in 9% of the animals, but this was about half the rate seen in studies of standing, open castration techniques, he said.

They also noticed less hemorrhaging in the castrated horses and ponies, said Koch. However, two donkeys experienced severe hemorrhaging. It’s possible that donkeys and mules need a different kind of technique, probably involving spermatic cord ligation, due to their larger and more fragile testicular vessels, he added.

While Koch said the thought might seem terrifying (possibly even leading to a bias against the technique by veterinarians themselves) the power drill has clear advantages, he noted—it just takes some getting used to.

“We’re all more used to a nice clamp (an emasculator) that crushes the cord,” he said. “But that’s also quite brutal if you think about it. Now, instead of crushing the cord, we’re applying a similar-looking clamp that just has to be twisted around its long axis to work. That’s where the hardware store tool comes into play.”

The study, “Complications associated with closed castration using the Henderson equine castration instrument in 300 standing equids,” was published in Veterinary Surgery.