Horse News

Why PZP and wild horses do not belong together

by Craig Downer as published on HorseTalk

The use of the contraceptive agent PZP can seriously compromise the natural adaptation of wild horses, writes wildlife ecologist Craig Downer. This, he suggests, subverts the true intent of the Wild Free Roaming Horses and Burros Act, passed in 1971 to safeguard the animals.

Captured Kiger Horses at BLM Burns facility.

Many serious damaging effects upon wild horses and burros are caused by PZP (Porcine Zona Pellucida) administration. These effects pertain both to the mares who are injected with this inoculation, either manually when held captive or remotely by darting with a rifle in the field aimed at the hip and to the rest of the band whether stallions, other mares or young.

These effects have been documented and analyzed by professional biologists, and many ordinary people have also observed and reported them. An honest reading of the Wild Free-Roaming Horses and Burros Act (WFHBA) should reveal how out of tune PZP interference is, for it violates the most intimate parts of mares and causes an aftermath of stress, anguish and social disruption. It should be considered antithetical to this law’s core intent. Basically, PZP interference with the natural lives of the wild horses (or wild burros) is a form of domestication that contradicts the WFHBA, which mandates “minimum feasible management” and that the horses and burros be allowed to become “integral” parts of the public lands’ ecosystem where they attain a “thriving natural ecological balance”. To those who hold the noble purpose of this law in high esteem, what has and continues to happen is both a shame and a disgrace to America! This is an intolerable situation that needs to be quickly corrected…(CONTINUED)

9 replies »

  1. So for those of us who are still learning … what is a “pesticide” versus a “vaccine”?
    By definition, a pesticide is a product designed to DESTROY organisms deemed to be undesirable or noxious.
    PZP or brand name ZonaStat-H, EPA Reg. NO. 86833-1, was approved for use in wild burros and horses by the EPA. ZonaStat-H is a PESTICIDE, registered in January 2012 by The Humane Society of the United States.

    Chemical or biological substance designed to KILL or retard the growth of pests that damage or interfere with the growth or crops, shrubs, trees, timber and other vegetation DESIRED BY HUMANS. Practically all chemical pesticides, however, are poisons and pose long-term danger to the environment and humans through their persistence in nature and body tissue. Most of the pesticides are non-specific, and may kill life forms that are harmless or useful.
    Any preparation used as a preventive inoculation to confer immunity against a specific DISEASE usually employing an innocuous form of the disease agent, as killed or weakened bacteria or viruses, to stimulate antibody production.

    PZP is NOT a vaccine … it is a PESTICIDE.

    The BLM and USFS & HSUS make it sound like they are helping to prevent a disease when they are actually supporting the eventual demise and extinction of our wild horses and burros.
    See for yourself:

    Click to access fs_PC-176603_01-Jan-12.pdf


  2. the real reason why PZP and wild horses don’t belong together is the failure to amend Resource Management plans. See attached.

    On Tue, Mar 24, 2020 at 3:32 AM Straight from the Horse’s Heart wrote:

    > R.T. Fitch posted: “by Craig Downer as published on HorseTalk The use of > the contraceptive agent PZP can seriously compromise the natural adaptation > of wild horses, writes wildlife ecologist Craig Downer. This, he suggests, > subverts the true intent of the Wild Free Roaming ” >

    Liked by 1 person

  3. sure don’t agree w/this article – on the range birth control is about the only saving grace they have to stay on the range…… it is a disgrace that the BLM is abusing it’s authority like they have been doing all along with our wild horses!!! BUT doing nothing means even more round-ups!


    • It’s important to recognize that the overall numbers are not independently verified even today, nor are mortality rates from all sorts of causes. It’s also important to step back and recognize that endlessly reducing legal areas will make even a small population seem “excess” as the resources of necessity are hit harder. It’s also true that all (or nearly all) remaining legal areas our wild horses and burros are even allowed to exist as protected also permit private livestock grazing at below market and massively subsidized rates. This is an intentional management strategy that overstates the equid impacts and blatantly ignores those of for-profit livestock grazing on public lands.

      Ask yourself why the logical step of simply making the 12% of all public grazling lands which can include wild horses and burros off limits to livestock? If we separate these “managed” species we can more clearly monitor the impacts, but have to recognize the past 50 years or so of this cockeyed “management” strategy have made lasting changes to the rangeland ecosystems. One answer might be to move wild horses back into areas long since emptied of them, and not allow any livestock there, then document and monitor (with independent verification) extensively. This would go a long way towards restoring public faith in the integrity of the BLM and their paid efforts on our behalf. As it stands now, the effort is always a one-way creative extermination plan. This is not management, it is a stupendous failure.

      Liked by 1 person

  4. The Economist
    Letter to the editor
    August 2016
    Marybeth Devlin

    The Big Lie of “overpopulation” is the pretext for BLM’s war against the wild horses. It’s BLM’s version of the “Shock Doctrine,” wherein BLM concocted a phony crisis to push through policies antithetical to the Wild Horse Act against the will of The People.
    In fact, horses are a slow-growth species when it comes to reproduction. The gestation-period lasts over 11 months, and a mare produces just 1 foal. While an independent study of BLM’s records did confirm a nearly 20% birth rate, that study also found that 50% of foals perish before their first birthday. Thus, the effective increase in population from new foals is just 10%. However, adult mortality must also be taken into consideration. Adult mustangs succumb at a rate of at least 5% a year. So, what is a normal herd-growth rate? Around 5%, probably less. Thus, a herd could not double in 4 or 5 years, debunking another BLM falsehood. But BLM stealthily inserts herd-growth rates far higher than 20% in its reports — biologically-impossible herd-growth rates. For instance, in Wyoming, BLM declared that the Salt Wells Creek herd grew from 29 horses to 616 horses in 6 months (yes, months), a 2,024% increase. BLM’s “data” is chock-full of preposterous growth-estimates. So, when you hear talk of how the wild horses are reproducing “exponentially,” that’s a sure sign that BLM has falsified the data. You should also know that the National Academy of Sciences was required by the terms of its grant to draw conclusions per BLM’s figures — the falsified figures. The NAS was not allowed to collect data independently. Thus, BLM wired the results to confirm its lies.

    Liked by 1 person

  5. Letter to the editor (continued)
    August 2016
    Marybeth Devlin

    Wild horses are underpopulated. Per the guidelines of BLM’s own geneticist, more than 80% of the herds suffer from arbitrary management levels (AMLs) set below minimum-viable population (MVP). Low AMLs enable BLM to claim an “excess” in herds whose numbers, even if they were over AML, would still not reach MVP. So being “over AML” is meaningless as well as misleading. But those low AMLs, combined with fraudulent, biologically-impossible herd-growth estimates, give BLM an excuse to scapegoat those few wild horses for the range-damage done by the millions of livestock that overgraze the public lands.

    PZP is a potent weapon in BLM’s arsenal — for its biological warfare against the wild horses. PZP is a registered pesticide. Its mechanism-of-action is to cause auto-immune disease — tricking the immune system into producing antibodies that target and attack the ovaries. The antibodies cause ovarian dystrophy, oophoritis (inflammation of the ovaries), ovarian cysts, destruction of oocytes in growing follicles, and depletion of resting follicles. The mare’s estrogen-levels drop markedly as PZP destroys her ovaries. Ultimately, PZP sterilizes her. A recent study — which included the McCullough Peaks herd — found that PZP extends the birthing season to nearly year-round. Out-of-season births put the life of the foals and the mares at risk. Worse yet, radioimmunoassay tests indicated that PZP antibodies are transferred from mother to female offspring via the placenta and milk.

    Liked by 1 person

  6. The Economist
    Letter to the editor (continued)
    August 2016
    Marybeth Devlin

    As for the wild horses held in captivity, they are the “legacy” of former Secretary Salazar’s equid cleansing era, during which he had tens of thousands of wild horses removed from the range. However, the mortality rate of captive wild horses is about 8% a year. So, obviously, since they are not reproducing, their numbers will steadily drop, showing that BLM’s billion-dollar figure for their care was bogus — it was just another Lie. But that Lie has ballooned. BLM has taken the $1 billion figure that it originally announced, multiplied it by 230%, and then multiplied that number by another 200%, amplifying the fraud. When BLM lies, it lies Big.
    The Wild Horse and Burro program, if administered per the minimum-feasible management-model specified by Law, would not cost much at all. BLM does not lack for resources. There are 22 million acres of legally-designated wild-horse herd areas — which BLM previously took away for political expediency — that can be reopened as habitat. The horses now held captive can be released to those areas, where the cost of their upkeep will be $0.

    Liked by 1 person

  7. The Economist
    Letter to the editor (continued)
    August 2016
    Marybeth Devlin

    Contrary to BLM’s disinformation campaign, wild horses do have natural predators — mountain lions, bears, wolves, and coyotes. But those predators are persecuted mercilessly. The government exterminates what the hunters don’t shoot. However, the International Society for the Protection of Mustangs and Burros — Wild Horse Annie’s foundation — notes that even without predators, their wild-horse herds self-regulate their numbers, with population-growth in the single digits.
    Finally, adoptions have not declined. It’s just that BLM used to count sales-for-slaughter as “adoptions.” Now, only “forever-family” placements qualify. However, mustangs are not homeless horses.
    They are wild horses whose home is on the range.

    Liked by 1 person

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