Wild horse plan under review

Wild horses in the Warm Springs Herd Management Area near Burns, OR.

A proposed research program to spay wild horses could begin by the end of November in Oregon. The research project led by the U.S. Geological Survey and Bureau of Land Management could also include Colorado State University (CSU).

The project would evaluate the safety complication rate and feasibility of ovariectomy via colpotomy on wild horse mares and the impacts to mare and band (herd) behavior once they are returned to the range as compared to an untreated herd.

The BLM prepared an environmental assessment (EA) and accepted public comments during a 30-day period that ended July 30, 2018. Those comments are under review, according to Tara Thissell, BLM public affairs specialist in Hines, OR.

Thissell told WLJ approximately 8,300 comments were received with the bulk being form letters signed against the project. In calling for comments, BLM made clear that similar comments or form letters would be considered as one comment and summarized with one response given. In addition to the form letters, she said comments both for and against the project were received.

The comments won’t determine if the project moves forward or not, Thissell said. “Comments are meant to convey public support or concern and the specifics of those opinions, as well as evidence of suggested alternatives or other means to accomplish the project needs. The decision, which is issued by the BLM, will show if/how the BLM is choosing to move forward on the project.”

She added that the decision could be appealed by a person or group in opposition to the project, in which case the timeline for implementation could be determined by the courts and/or BLM agency policies, depending on the nature and content of the appeal.

A number of wild horse advocates have expressed concern for the project, claiming the health and wellbeing of horses will be put at risk.

Asked for information about CSU veterinarians involved with the project, Thissell told WLJ those involved are “extremely experienced with large animal surgery and have decades of experience.” However, citing the Privacy Act of 1974, she said, “The government is not authorized to release the names of private individuals involved with this proposed project.”

In reviewing the CSU Institutional Animal Care and Use Committee Animal Use Application, WLJ found a redacted document blocking the names of individuals and departments. In another attempt to identify those involved, WLJ contacted Karen Dobos, director of the Research Integrity and Compliance Review Office at CSU, who said she was unable to respond to direct questions. But she did offer a general response, saying, “Most importantly, CSU continues to be committed to performing research with the highest technical and ethical standards and complies with all state and federal laws and guidelines for the use of animals in research.”

In referencing other reports on the project, Dobos said, “We believe that information about the study is not factually represented in some information sources. Colorado State University’s internal process for participation in this study has included a rigorous review of the methods and protocol directly involved in this project, as well as a review of current research evidence related to procedures proposed in this study, all with animal welfare as our top priority. Our university is committed to the short-term as well as long-term health of this herd and the individuals within the herd. Our involvement in this study is based on scientific evidence that supports the best interests of the animals involved.”

BLM said finding a workable population control is important because the current herd numbers exceed the recommended appropriate management level by more than 585, putting a strain on rangeland resources. It estimates by the fall of 2018 there will be approximately 738 adult wild horses, plus approximately 147 foals and 49 adult burros and foals residing in and around the Warm Springs Herd Management Area (HMA) near Burns, OR. (This study will not involve burros.)


The proposed procedure, ovariectomy via colpotomy, is a standard procedure used for domestic horses and is generally considered less invasive than a typical spay procedure used for domestic cats and dogs. The procedure takes fewer than 15 minutes to complete and is more cost-effective than available short-term fertility control vaccines.

The cost of spaying, according to Thissell, is approximately $250–$300 per mare and includes the expense of the antibiotic ($30 per dose), the sedation drugs, and the veterinarian’s labor and travel.

Injectable fertility treatment using PZP-22 costs approximately $500 per mare treated. This includes the costs of one dose of liquid primer (similar to ZonaStat-H used for remote darting) and one dose time-release pellets; plus holding and application costs—approximately $5 per day per horse. ZonaStat-H costs approximately $35 per dose.

Pros and cons

Thissell briefly outlined some of the pros and cons of the fertility treatment options.


  • Pros—reversible.
  • Cons— repeated roundups, repeated treatment, increased chance of injury to horses or employees, high costs with repeat gathers and application, annual remote darting changes the behavior of the mare, remote darting is not feasible in late winter/early spring on most HMAs.


  • Pros—Permanent, mare only needs to be gathered once in her life for treatment, costs less than one dose of PZP-22.
  • Cons—As with any surgery, chances of infection or other complications.

BLM said that its nationwide effort includes investing in a diverse portfolio of research projects to develop new, modern technologies and methods to improve management, slow the wild horse and burro population growth rates and reduce the need to remove animals from public lands. The studies are in response to a 2013 recommendation from the National Academy of Science to develop new or improve existing population growth suppression methods for wild horses and is in accordance with The Wild Free-Roaming Horses and Burros Act of 1971.

Asked if this project could be a test case for other HMAs, Thissell reiterated that this project is intended to evaluate the safety, complication rate and feasibility of ovariectomy via colpotomy on wild horse mares and the impacts to mare and band behavior once returned to the range as compared with an untreated herd.

She added, “Depending on the outcome of the research, ovariectomy via colpotomy could be an effective tool for managing population growth on the range. This study represents a feasibility approach, and the results are not policy setting for BLM. Any future proposal by BLM to utilize the spay method analyzed in this EA would be subject to NEPA [National Environmental Policy Act] compliance.”

The decision is expected in mid-August and will be posted online at eplanning.blm.gov/epl-front-office. — Rae Price, WLJ editor

WLJ Editor

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