GonaCon™ — To Be Used against Wild Horses — An Overview

GonaCon™ is an EPA-registered, immuno-contraceptive pesticide.  Its classification is “restricted-use” due to “non-target injection hazard.”  EPA warns that “pregnant women should not be involved in handling or injecting GonaCon and that all women should be aware that accidental self-injection may cause infertility.”  Children are not allowed in areas where the product is used. [4, 6]  Please keep in mind that the GonaCon™ dose-in-question is meant for a horse.

GonaCon“works” by causing an auto-immune disorder.  Behaving like a perverted vaccine, GonaCon tricks the immune system into producing antibodies that destroy a female’s gonadotropin-releasing hormone (GnRH).  Without GnRH, a female does not produce sex hormones, does not come into estrus, and is thus infertile.  Behaviorally, courtship-rituals cease. [1, 3-6]

For those wild-horse-and-burro advocates who oppose the other immuno-contraceptive — PZP — you will be disturbed to learn the following from the USDA-APHIS “Questions and Answers” sheet regarding GonaCon™:

“After evaluating GonaCon™, the Food and Drug Administration (FDA) … approved the slaughter of pigs vaccinated with GonaCon™.  Similar injectable hormone-altering products are used routinely in livestock applications.” [5]

Good grief.  So, the slaughterhouse pig ovaries used to manufacture PZP may very well come from animals who were previously injected with GonaCon™ to destroy their GnRH hormone — without which the ovaries cannot produce estrogen — and those poor pigs may also have been “routinely” injected with other similar “hormone-altering products.”  Then our wild horses and burros are injected with PZP, which itself causes a marked drop in estrogen after just three treatments. [2]  Surely, these hormonal atrocities constitute animal abuse.

GonaCon is long-acting.  The treatment-protocol, consisting of two injections administered 30 to 60 days apart, can cause infertility for as long as four-to-five years without the need for booster shots. [3, 5]  However, mares would still need to be rounded up and held captive for those 30 to 60 days to administer the injections properly.  If all females in a small herd were treated per the multi-year plan, it could result in an unintended consequence — a huge gap in the herd’s age-structure, because very few if any foals would have been born during that period.  Indeed, although the pesticide’s effectiveness was expected to diminish over time, a 3-year study of GonaCon-treated elk revealed that the percentage of infertile females actually increased each year, finally reaching 100%.  It was also noted that every one of the treated elk suffered an abscess at the injection-site. [1]

Because GonaCon stimulates the immune-system, it will elicit the greatest reaction — the greatest output of destructive antibodies — if a mare is blessed with healthy immune-function.  Such a mare will react strongly and be contracepted quickly.  But she could just as easily be sterilized.  In fact, GonaCon’s “application instructions” warn of the chance of sterilization. [5]

On the other hand, GonaCon may not work at all if a mare suffers from weak immune-function.  That mare’s immune system will fail to react to GonaCon™, and she will get pregnant in spite of it.  Thus, over time, there is the risk of another unintended consequence — selection for the immuno-compromised.  As Jenny Powers, a National Park Service wildlife veterinarian and one of three lead scientists who participated in the elk research commented: “Any time we’re manipulative with wild animals, we’re messing with natural selection.” [1]


Report prepared by Marybeth Devlin on December 18, 2015 for Protect Mustangs



  1.  Keller, Larry.  (2011, May 17)  To shoot, or not to shoot, at Rocky Mountain NP.  High Country News.  Retrieved from http://www.hcn.org/blogs/range/to-shoot-or-not-to-shoot-at-rocky-mountain-np

  2.  Kirkpatrick, J. F., I. K. M. Liu, J. W. Turner, Jr., R. Naugle, and R. Keiper.  1992a.  Long-term effects of porcine zonae pellucidae immunocontraception on ovarian function of feral horses (Equus caballus).  J. Reprod. Fert. 94:437-444.  Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/1317449

  3.  McGrath, Matt.  (2011, September 1)  “Deer ‘pill’ curbs aggressive mating.”  BBC News.  Retrieved from http://www.bbc.com/news/science-environment-14744811

  4.  United States Environmental Protection Agency.  (2009)  Pesticide Fact Sheet.  Mammalian Gonadotropin Releasing Hormone (GnRH).  Retrieved from http://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-116800_01-Sep-09.pdf

  5.  USDA-APHIS. (2006, May 1)  “GonaCon™—Birth Control for Deer: Questions and Answers.”  Digital Commons@University of Nebraska – Lincoln.  Retrieved from http://digitalcommons.unl.edu/usdaaphisfactsheets/7/

  6.  U.S. Department of the Interior.  (2015)  Review of Ungulate Fertility Control in the National Park Service.  Retrieved from https://www.nature.nps.gov/biology/wildlifehealth/Documents/Ungulate%20Fertility%20Report_09242015.pdf

Protect Mustangs is an organization who protects and preserves native and wild horses.

5 thoughts on “GonaCon™ — To Be Used against Wild Horses — An Overview

  1. the human species is out of control, we need to pull ourselves back and take stock of our behavior toward other beings – we are cruel, narcissistic and immoral in our actions.

  2. Frankly, we knew some time back about the GonaCon, and the subject was brought up in the matters of Indirect-Proportional-System-Stimuli (IPSS) into the population, due to over-population of humans. Sky-based as well as land-based situations were discussed, but rejected.

    The Republicans, I and others heard, were opening the door to the previous summaries and information of meetings and notes taken many years ago — the changing tide of politicians, mostly the Republican’s but Democrats involved as well — re-opened the doors to a situation that was REJECTED YEARS AGO, and due to lack of Ethics as well as immoral to place into a social environment of many people — in order to indirectly control birth rates — or reduce them.

    The Wild Horses, I repeat, are nothing more than deception, and the supporters of all of the Birth control schemes, BLM-DOI-USDA-etc. and their supporters, simply piss-poor American’s so ignorant they do not see what they are doing to our country what so ever! Ethics and morals escape these individuals. The hiring principles, as well as the testing, for government employees in these agencies is also under scrutiny. As there exist elements that clearly promote questionable character within employment, overshadowed by a willing personality to follow, rather than see the questionable conduct indeed wrong.

    America! We have a Problem.

  3. BLM’s strong promulgation of PZP ( derived from the ovaries of pigs treated with Gonacon) -based birth control jives perfectly with their master strategy the goal of which is the radical reduction of wild horse & burro herds in the short term, and the extinction of many of them in the long term. Hence their apparent indifference to the serious potential for permanent sterilization in lieu of temporary birth control.

  4. This is disgusting and has to stop, humans are now going too far its barbaric and just wrong and those supporting such acts are lacking any intelligence and are showing mass ignorance, This has to be stopped there needs to be public investigations and the people of the USA and the world deserve to know the truth of what is being done there.

  5. James Howie I totally agree with you. Totally. Humans should not be called human any more. They should be called monsters. Especially those that make up BLM. They have no heart and no soul. We are dealing with zombie monsters with no feelings for these beautiful spiritual beings that God created for our own happiness. Can you imagine a world without these graceful horses? They are not food. They were not sent to us to feed on. If we believe in God all we have to do is look into their eyes. In those eyes we shall see God our Lord and Creator staring back at us. The thing is, to be pragmatic, what are we going to do to stop this insanity? How can we stop it? Who is going to do the public investigation? I am willing to call my Representative in Washington and ask him why this is allowed to continue. What evil people in the government condone this? Are there others willing to do the same? Willing to call their representative and make pertinent statement that this has to stop and if doesn’t we are willing to take our case on the air if need be for the people of this country to be informed what Washington is doing to our beloved horses. I can’t think of anything else to make an impression and give BLM food for thought. We have to do something. We can’t sit back and take it any more.

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