About PZP....

Wild Horse Birth Control Effective But Not Panacea
Powell Tribune 12/30/08

PZP (Porcine Zona Pellucida) is a fertility control drug administered to female horses (mares) for the purpose of slowing population growth. Still classified as experimental, its development and progress has been well documented in a variety of scientific journals and studies.

In response to the Powell Tribune article, Dr. Jay Kirkpatrick, Director of The Science and Conservation Center as well as a prominent leader and authority on PZP for the last few decades, has provided a variety of articles related to PZP to increase understanding and provide clarification to many of the points posted in the article linked above.

Dr. Kirkpatrick also added these personal comments pertaining to the article.

"The idea that the genetic makeup of a western horse is sufficiently different from ASIS horses to make a difference in the response to the vaccine is absolutely in error. The vaccine has worked the same way, with the same efficacy in close to 40 different herds throughout the United States. On the Return to freedom herd, which is composed of horses from all over the west, efficacy is no different than anywhere else. Finally, the idea of horses from different genetic backgrounds responding differently flies in the face of conventional immunological wisdom. That aside, current data refutes that idea."

"The issue of 16 of the 34 treated mares not yet foaling is actually good news but must be put into context. The first consideration is that these are long-acting forms of the vaccine that were put into the McCullough Peaks horses and we are still learning how effective they are. BLM wants a four-year vaccine anyway. Second, the only alternative is to remove horses and that removes the genes permanently, without any chance of recovery. One cannot look at contraceptive effects in horses fairly or in any meaningful way without looking at the effects of all alternative management options."

"Finally, if those horses that have not returned to fertility have already produced foals, there is no need for them to produce more. I have attached a second paper that should also be distributed to all parties. It illuminates the idea of measuring effects of all management options rather than focusing on one. It is interesting that the genetic issue arises here, because contraception is about a light year ahead of gather/removal in protecting the genetic integrity of the horses."

"One last note. If humane management is a concern, I suggest everyone read carefully the third attached paper, on increased longevity in treated horses."

Dr. Patricia M. Fazio, Statewide Coordinator for the Wyoming Wild Horse Coalition, who has worked with Dr. Kirkpatrick on several issues pertaining to horses and wild horse management added,

"Some information contained in this piece is outdated, erroneous, and appears to be unanalyzed raw data. Please note that porcine zona pellucida is PZP not “PZB.” Perhaps immunocontraception now looks better to the BLM than long-term holding, after all. Let us hope for humane, scientific management of federal wild horses in the new Administration."

"Please post your comments about wild horses and BLM management on the Obama-Biden Transition Team Website: Praise the Transition Team for their proposed ban on earmarks within federal legislation… at least those that do not receive public review, such as the Burns Amendment."

Here are the links to the articles Dr. Kirkpatrick referenced above.

Achieving Population Goals in a Long-Lived Wildlife Species (Equus caballus) with Contraception: Jay F.Kirkpatrick, Wildlife Research, 2008, 35, 513-519 CSIRO Publishing

Measuring The Effects of Wildlife Contraception: The Argument for Comparing Apples with Oranges:
Jay F. Kirkpatrick, Viewpoint, Reproduction, Fertility and Development 2007, 19, 548-552, CSIRO Publishing,

Immunocontraception and Increased Longevity in Equids:
Jay F. Kirkpatrick (1*) and Allison Turner (2); (1*)The Science and Conservation Center, Billings, Montana, (2) Assateague Island National Seashore, Berlin, Maryland, Research Article, Zoo Biology 26:237-244 (2007), Wiley InterScience.

PZP Q&A Final (Short Form) July 7,2006

PZP Q&A Final (Long Form) July 7, 2006

Fact Sheet on BLM's Wild Horse and Burro Fertility Control Program
U.S. Department of the Interior, Bureau of Land Managment,
Annotations by Patricia M. Fazio, Ph.D., July 2008

Photo taken from Annual Report for 2004 Wild Horse Research and Field Activities, United States Geological Survey (USGS) in cooperation with the BLM, By Jason Ransom, Francis J. Singer, and Linda Zeigenfuss, Open-File Report 2005-2005-1316, U.S. Department of the Interior.

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