New Nonsurgical Equine Sterilization Technique in the Works
With so few natural predators, feral horse populations—such as the Brumbies in Australia—are growing rapidly. But current immunocontraceptive (drug-induced sterilization) techniques, used to control herd growth, must be readministered every one to three years, which can be a difficult task when managing hundreds or thousands of horses. So, researchers in Australia are studying new ways to help control feral horse populations in that country.

The research team is hot on the trail to developing a novel, practical, and cost-effective sterilization product for free-ranging horses that’s also welfare-friendly. What they’re after: a “one-shot” administration that sterilizes both mares and stallions—for life.

“It is very important that we develop a method that offers an effective solution to the feral horse problem, while ensuring humane practices and public approval is achieved,” said Sally Hall, a PhD candidate at the University of Newcastle’s Priority Research Centre for Reproductive Science, in New South Wales, Australia, and Invasive Animals Cooperative Research Centre scholarship recipient.

Under the supervision of John Aitken, PhD, and Brett Nixon, PhD, Hall has been working to develop this “one-shot” sterilization method over the past four years. While the actual product might still be several years away, the research team is already testing “promising technologies” in a laboratory setting.

“The nonsurgical sterilization methods we are trying to develop have the potential to vastly improve the value of animal life, which I feel is a great triumph for society,” Hall said.

In a recent review, the researchers honed in on three technologies with a strong potential to lead to one-shot nonsurgical sterilization. These include:

  • Redox cycling. This technique generates “oxidative stress” in the testicles and ovaries, causing permanent DNA damage to immature eggs and sperm;
  • Random peptide phage display. This technique specifically targets germ cells (immature eggs and sperm) within the testicles and ovaries to induce programmed cell death; and
  • Autoantibody generation via covalent modification. This technique uses sperm proteins that have been covalently modified (altered using enzymes as catalysts), as opposed to “native” (unmodified) sperm, in the immunizations. The result is a significantly greater immune response than what occurs when only immunizing with native sperm proteins.

In addition to requiring frequent administration, some currently available immunocontraceptives can also affect normal behavior, Hall said. Studies have shown that some treatments have “altered reproductive behaviors that are integral to the maintenance of the complex social structure of herd animals such as horses,” the authors reported.

Hall said the technologies in development give hope for a safe, effective, single-dose solution that doesn’t affect natural behavior.

Once available and widely tested, the technique could even be used for domestic animals, including horses, dogs, and cats.

“The beauty of these technologies is that we may one day be able to take our pet into a vet clinic to be desexed with a simple injection rather than surgery,” said Hall.

The study, “Non-surgical sterilisation methods may offer a sustainable solution to feral horse (Equus caballus) overpopulation management in Australia,” was published in Reproduction, Fertility and Development.