FACT SHEET: The Truth about PZP

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EXPANDED SUMMARY OF PZP’S ADVERSE EFFECTS, INCLUDING REFERENCES

PZP — The Pesticide

Porcine zona pellucida (PZP aka ZonaStat-H or Native PZP) is an EPA-registered pesticide derived from the ovaries of slaughtered pigs. PZP is approved for use on wild horses “in areas where they have become a nuisance ….” [20]

Some persons argue that, because PZP does not kill the mare, it is not really a “pesticide.” Actually, PZP does kill. As will be documented in this report, its use is associated with stillborn foals. In the long term, PZP will weaken a herd immunologically, which could swiftly lead to its extinction. So, yes, PZP is a real pesticide.

PZP — an Anti-Vaccine

While touted as a “vaccine,” PZP is actually a perversion of what a true vaccine is supposed to be. Instead of preventing disease, PZP causes disease — auto-immune disease. Thus, PZP is an anti-vaccine.

PZP’s Mode of Action as Stated in the Pesticide Registration Is a Disproved Hypothesis

The registrant of PZP advised the Environmental Protection Agency (EPA) that, based on information from the pesticide’s researcher-manufacturer, PZP works by generating antibodies that “block sperm attachment.” This representation of PZP as a sort of chemical condom was not fact but merely an untested hypothesis, postulated three decades ago. The old hypothesis was disproved by subsequent research. PZP’s manufacturer knew, or should have known, this. The manufacturer should also have been informed and up-to-date regarding the side effects and unintended consequences of PZP. Yet, the manufacturer continued to cite the disproved hypothesis and to deny that PZP has any adverse effects. [7 and 13]

PZP’s True Mode-of-Action

So how does PZP really work? PZP tricks the immune system into waging war on the ovaries. In a meta-analysis of ZP-type contraceptives, Kaur & Prabha (2014) reported that the infertility brought on by such products is ” … a consequence of ovarian dystrophy rather than inhibition of sperm-oocyte interaction.” Thus, PZP’s antibodies “work” not by blocking sperm attachment but by destroying the ovaries. Kaur & Prabha further disclosed that ” … histological examination of ovaries of immunized animals revealed the presence of atretic follicles with degenerating oocytes.” [5] [Atretic follicles are ovarian follicles in an undeveloped state due to immaturity, poor nutrition or systemic disease; manifested by prolonged anestrus.]

Kaur & Prabha’s review concluded that PZP’s antibodies induce ovarian dystrophy, oophoritis (inflammation of the ovaries), destruction of oocytes in all growing follicles, and depletion of resting follicles. The manufacturer of PZP as well as Bureau of Land Management (BLM) should have been aware of these and other findings about the pesticide. Yet they ignored or disregarded any information that was contrary to their personally-preferred but obsolete and false description of PZP’s mode-of-action.

PZP Manufacturer’s Own Research Found Markedly Depressed Estrogen Secretion

In a telling study published back in 1992, the manufacturer of Native PZP, along with colleagues, reported that ” … three consecutive years of PZP treatment may interfere with normal ovarian function as shown by markedly depressed oestrogen secretion.” [6] Thus, despite all the hype about PZP being non-hormonal, the manufacturer knew that ZonaStat-H has an adverse hormonal effect, causing significantly-lowered estrogen. Thus, PZP is an endocrine disruptor. [21] The plummeting estrogen-levels may also reflect the ovarian dystrophy and oophoritis now known to be caused by PZP. Despite personally discovering negative hormonal impacts 23 years ago, PZP’s manufacturer continued to cite misinformation regarding the product’s mode-of-action and endocrine-disruptor side-effects.

PZP Causes Ovarian Cysts

In their 2010 meta-analysis, Gray & Cameron cited a number of studies that found ” … alterations to ovarian function, oophoritis, and cyst formation with PZP treatment (Mahi-Brown et al.1988, Sehgal et al. 1989, Rhim et al. 1992, Stoops et al. 2006, Curtis et al. 2007).” [4] These findings support those of Kaur & Prabha while introducing yet another adverse effect: ovarian cysts. Gray & Cameron’s review also noted that increased irritability, aggression, and masculine behavior had been observed in females following PZP-treatment.

PZP → Endocrine Disruptor → Elevated Testosterone → Masculinizing Effects

Recall that PZP has endocrine-disrupting effects that result in lowered estrogen. Per the observed masculine behavior of treated mares, PZP seems to have a testosterone-elevating effect too. A deficit of estrogen alone would not necessarily manifest in the masculinization of treated females, but an excess of testosterone would. So, it appears that PZP disrupts at least two hormones: estrogen — by substantially lowering it — and testosterone — by substantially elevating it. Adverse effect: Unnatural behavior.

PZP → Ovarian Cysts → Elevated Testosterone → Masculinizing Effects

As discussed above, PZP correlates with abnormal masculine behavior on the part of treated females, a side-effect likely due to elevated testosterone. But in addition to the endocrine-disruption caused by PZP, there could be a second way for testosterone levels to become elevated. Recall that PZP causes ovarian cysts. An Internet search on “ovarian cysts and testosterone” yielded results for polycystic ovary syndrome (PCOS) in women. Interestingly, one of the symptoms of PCOS is high testosterone levels. [12 and 22] The connection between ovarian cysts and elevated testosterone suggests that the ovarian cysts caused by PZP could — either alone or in combination with PZP’s endocrine-disruptor effects — lead to high testosterone levels in treated females, as evidenced by their masculinized behavior.

PZP Causes Additional Adverse Effects

Gray & Cameron’s review also disclosed that, when PZP was administered to the females of a herd, males lost body condition while the oft-claimed improvement in female body condition did not hold up. Further, mares remained sexually active beyond the normal breeding season and had more estrus events.

PZP Selects for Weak Immune Function

Gray & Cameron’s analysis raised the possibility of PZP selecting for immuno-compromised individuals. Here’s why. Because PZP stimulates the immune system, it ironically works “best” — sterilizes faster — in mares that have strong immune-function. Such mares respond to the anti-vaccine and produce quantities of PZP antibodies that destroy their ovaries. But, conversely, PZP may not work at all in mares whose immune-function is weak or depressed. Those mares fail to respond to PZP. They keep getting pregnant and producing foals who, like their dam, suffer from weak immune-function. So, the PZP pesticide works against the very horses that Nature has best equipped for survival against disease while favoring and selecting for the immuno-compromised. Thus, a herd being treated with PZP is undergoing selective breeding for weak immunity, which puts the population at risk for disease — and ultimately, for extinction.

PZP Confers Dubious “Benefit” of Increased Longevity

Gray & Cameron also cited a study that found that “… PZP treated feral horse mares lived longer, resulting in a new age class (>25 years) not present before treatment ….” Exceptionally-long life is an ironic effect of PZP treatments. PZP’s manufacturer actually boasts about it, as if the anomaly were a good thing. However, Gray & Cameron questioned the supposed benefit of mares living much longer than their normal life expectancy. Indeed, such mares take up scarce slots within size-restricted populations. The ultra-elderly mares continue to consume resources for many years, but they no longer contribute to the gene-pool. It is detrimental to a population’s genetic viability to carry significant numbers of sterile herd-members way-beyond their normal life-span.

Research on Wildlife Contraceptives Revealed Stillbirths and Auto-Immune Oophoritis from PZP

There was an even earlier, definitive meta-analysis on wildlife contraceptives. Nettles (1997) reviewed 75 studies available at that time on the subject. Among his findings regarding PZP-use across different species, including horses, were: Stillbirths; altered ovarian structure and cyclicity; interference with normal ovarian function; permanent ovarian damage; and some cases of irreversible sterility due to auto-immune oophoritis, which suggested that PZP can be selective against a certain genotype in a population. [10] Many of these findings were confirmed by Kaur & Prabha as well as by Gray & Cameron. Please keep in mind these key findings: Stillbirths, and auto-immune oophoritis.

Recent Stillbirths Correlated with PZP

There is recent evidence confirming Nettles’ finding of a correlation between PZP treatments and subsequent stillbirths. In June 2015, Karen Sussman, President of the International Society for the Protection of Mustangs and Burros, reported that 7 mares previously treated with PZP at ISPMB, when taken off PZP, were able to get pregnant. However, 6 of those 7 mares — that is, 86 percent — produced foals that were stillborn. All other ISPMB mares that had not been injected with PZP successfully birthed healthy foals. Thus, given that environmental and other conditions were identical, the only variable was PZP. The dead foals have been sent to a university pathology department for autopsy. [18]

Autoimmune Oophoritis Induced by PZP

Research by the Rose-Cihakova-Caturegli Laboratory at Johns Hopkins Pathology found: “Automimmune oophoritis can be induced by immunization with testis and ovarian antigen murine human zona pellucida 3 peptide (pZP3) in adjuvant.” [16] Here again, is causation of autoimmune disease by a ZP-type product. This finding confirms other research cited herein.

Autoimmune Oophoritis and Risk of Other Autoimmune Diseases

A study by Varras et al. disclosed that, in humans, autoimmune oophoritis carries the risk of the patient developing other autoimmune diseases. [23] The correlation between autoimmune oophoritis and subsequent other autoimmune disorders weighs against injecting fillies and mares with PZP repeatedly and en masse.

Prolonged Breeding Season, Unusually-late Parturition Dates with PZP

Nettles’ meta-analysis on PZP disclosed other adverse effects: A prolonged breeding season and unusually-late parturition dates. (Parturition is the formal term for “giving birth.”) These findings have recently been confirmed, as is discussed below.

Parturition-Season Extends to Nearly Year-Round When a Herd Is Treated with PZP

A longitudinal study (Ransom et al. 2013) of three herds currently being managed by PZP — Little Book Cliffs, McCullough Peaks, and Pryor Mountain — found that the the parturition season lasted 341 days. [15] Ransom et al.’s finding of a nearly year-round birthing season supports the earlier finding by Nettles. Thus, during its period of potential reversibility, PZP’s effects wear off unpredictably. Out-of-season births put the life of both the mare and the foal in jeopardy. Nature designed the equine birthing-season to occur in Spring, not year-round, and certainly not in the dead of Winter.

Prolonged Delay in Recovery of Fertility

The same longitudinal study by Ransom et al. found that, after suspension of PZP, there was a delay lasting 411.3 days (1.13 years) per each year-of-treatment before mares recovered their fertility. What this means is that it takes that long, on average, for the ovaries to heal, to clear out all those cysts, and to regain some degree of normal hormonal function.

The question is: How is the delay in recovery-of-fertility addressed by BLM management practices? Answer: BLM ignores it. For instance, BLM currently administers PZP to Pryor Mountain’s fillies and mares starting at age 1½ — whom BLM artfully describes in the Environmental Assessment as fillies “becoming two year olds” — through age four. Thus, these fillies and mares receive intentional treatments for four consecutive years before being allowed the privilege of reproductive potentiality. Per Ransom et al.’s study, the Pryor Mountain fillies and mares would be expected to need 1,645.2 days (4.51 years) to regain reproductive capacity. But BLM gives the Pryor Mountain mares only 5 years off PZP before they are put back on it again — for the rest of their life. Thus, these fillies and mares might have just a six-month window — at best — in which to conceive. Due to the unpredictable timing of PZP’s wearing off, for some mares that window of fertility will close before they get a chance to produce a foal. Those mares’ genetic contribution will be zero.

As if the above scenario were not bad enough, PZP’s manufacturer conceded that it could take up to eight years to recover fertility after just three consecutive PZP treatments. [13]

Ransom Advises Proceeding with Caution regarding PZP

The Ransom et al. study warned: “Humans are increasingly attempting to manage the planet’s wildlife and habitats with new tools that are often not fully understood. The transient nature of the immunocontraceptive PZP can manifest into extraordinary persistence of infertility with repeated vaccinations, and ultimately can alter birth phenology in horses. This persistence may be of benefit for managing overabundant wildlife, but also suggests caution for use in small refugia or breeding facilities maintained for repatriation of rare species.” [15]

Because BLM keeps over 70 percent of the herds at levels below minimum-viable population (MVP), most herds qualify as “small refugia.” Pryor Mountain WHR is a small, isolated refuge, and its wild horses carry genes with rare alleles.

Ransom’s Exclusion of Seven Mares Evidences PZP’s Non-Effect on Immunocompromised Mares

In the “Data Collection” methodology section of the Ransom et al. report, the authors advised: “We omitted data for one female from the Little Book Cliffs and six females from McCullough Peaks because they produced offspring in every treatment year and thus were never effectively contracepted.”

This fact is important because it evidences PZP’s lack-of-efficacy on immunocompromised fillies and mares. To review: Because PZP activates the immune system, mares with naturally-low or depressed immune function do not “respond” to the treatment. It’s as if they had been injected with saline — their immune system is so weak that it does not react to the PZP by producing antibodies. The good news is such mares’ ovaries are saved from PZP’s destructive effects. The bad news is that these mares continue to become pregnant year after year, producing foals that will also tend to inherit low immune-function. Over time, the herd will become populated with more such low-immune horses because those with strong immunity get sterilized. Thus, PZP selects for horses with low immune function, which is bad for a herd in the long term. Even a routine infection could spread quickly and wipe out a population of horses with weak immune-function. If the goal is to preserve a herd, the use of PZP constitutes a worst management-practice.

BLM Was Fully-Aware of the Ransom Study but Suppressed the Findings

In their report, the authors of the Ransom et al. study gave a shout-out to BLM “for administrative and technical support throughout this project.” Thus, BLM was fully aware of the multi-year study while it was in progress and even lent support to it administratively and technically. Yet, in the case of the Pryor Mountain herd, BLM omitted this important report as a reference for the 2015 Environmental Assessment, which proposed intensifying the PZP “prescription.” Thus, BLM pretended that there was no such report and unethicallly suppressed it. Consequently, the public could not comment knowledgeably and appropriately on the continued use of — let alone the accelerated application of — PZP.

Three PZP Injections Can Trigger Sterility in Mares, or Just One Shot in Fillies Before Puberty

Disturbingly, another recent study on PZP (Knight & Rubenstein, 2014) found that ” … three or more consecutive years of treatment or administration of the first dose before sexual maturity may have triggered infertility in some mares. [9]

These findings are particularly troubling. They suggest that, actually, only two consecutive PZP-treatments may be reversible. Except, that is, in the case of fillies who have not yet reached puberty — they could be sterilized by just one injection. Recall the Pryor Mountain fillies, whose PZP treatments begin when they are just 1½ years old. They may not have reached puberty when they are initially treated. [1] And as we shall see later in this report, that first shot of PZP may not be their first shot of PZP.

Researchers Again Express Concerns about the Abnormal Life-Spans of Sterilized Mares

Knight & Rubenstein warned: “Inducing sterility, while relieving the mares from the energetic costs of lactation and reducing the stress from harem switching, may have unintended consequences on population dynamics by increasing longevity and eliminating the mares’ ability to contribute genetically.”

Knight & Rubenstein’s concerns support those of Gray & Cameron, who also questioned the supposed benefit of sterile mares’ extended life-spans. The abnormal numbers of aged, sterile mares count for census-purposes; but their presence disadvantages the younger horses, who become tageted for removal in order for BLM to achieve arbitrary management levels. Further, such mares no longer belong to the viable gene-pool.

PZP’s Destructive Antibodies Are Transmitted via the Placenta and Mother’s Milk

It gets worse. Sacco et al. reported that, per radioimmunoassay, PZP antibodies are transferred from mother to young via the placenta and milk. The transferred antibodies cross-react with and bind to the zonae pellucidae of female offspring, as demonstrated by immunofluorescent techniques. [17] These findings were disclosed in 1981. PZP’s manufacturer must have known about this dangerous effect, and certainly BLM should have investigated on its own whether there was any risk to the unborn or the nursing foal. Yet, the manufacturer continued to insist that there was no danger to the foal, whether born or unborn. [7 and 13] And in fact, BLM regularly administers PZP to pregnant and lactating mares, who transfer the destructive antibodies to their fetus, via the placenta, and to their foal, via mother’s milk.

Recall again the Pryor Mountain fillies. If their dams were injected with PZP while pregnant or nursing, such fillies will already have PZP antibodies cross-reacted with and bound to their zonae. Therefore, when those same fillies are injected at age 1½, it will be their second treatment, or potentially even their third. In fact, they could already have been sterilized in utero or while nursing, the treatment having been received prior to puberty, about which Knight & Rubenstein warned.

PZP Weakens Herd-Immunity, Posing Risk of Stochastic Events Leading to Herd-Extinction

To be self-sustaining, a herd needs to possess good immunity to withstand random catastrophes — known as stochastic events — such as contagious infections. There was such an event recently in Kazakhstan, where 120,000 endangered Saiga antelope — half the world’s population — died off suddenly and inexplicably within a two-week period. Scientists think a common bacterial infection was the cause of this mass-mortality event, but are unsure why the antelope were unable to fight off the disease immunologically. [14]

Imagine if such a catastrophe were to befall the Pryor Mountain horses, whose herd-immunity is being eroded by PZP. Note that the Saiga deaths involved antelope-mothers and their calves. If Pryor Mountain’s few fertile mares and their foals perished all of a sudden, that would leave just stallions and sterile old mares. The herd would be composed of the living dead, reproductively speaking, its rare alleles extinguished. BLM is failing to proactively manage the Pryor Mountain herd with stochastic events taken into consideration. That is malfeasance. PZP is a tool of immunological destruction, not of proper management.

PZP Continues the Use of Roundups and Removals

If the promise of PZP were true — if PZP really did eliminate the need to remove “excess” wild horses from the range — removals would have ended long ago in the Pryor Mountain Wild Horse Range, where PZP has been in use for approximately two decades. Yet removals are scheduled there with regularity every three years, the latest one in 2015.

Risks to Humans Who Administer PZP Injections

For staff and volunteers who inject wild horses with PZP, EPA’s Pesticide Fact Sheet advises that Personal Protective Equipment requirements include long sleeved shirt and long pants, gloves and shoes plus socks to mitigate occupational exposure. EPA specifically warns that pregnant women must not be involved in handling or injecting ZonaStat-H, and that all women should be aware that accidental self-injection may cause infertility. [20]

However, EPA’s Fact Sheet, the manufacturer’s training, and BLM’s operating procedures fail to inform pregnant women why it is so important that they strictly avoid PZP — because PZP’s antibodies cross the placenta and cross-react with and bind to an unborn female child’s own little zonae pellucidae. The baby-girl could be “anti-vaccinated” with PZP and even sterilized before birth.

EPA’s Fact Sheet, the manufacturer’s training, and BLM’s operating procedures fail to warn lactating women to avoid PZP and why — because PZP’s destructive antibodies would be passed along to a nursing female child via mother’s milk. The baby-girl could be “anti-vaccinated” with PZP and possibly sterilized simply from nursing.

EPA’s Fact Sheet, the manufacturer’s training, and BLM’s operating procedures fail to warn all women of the risk of ovarian dystrophy, oophoritis, ovarian cysts, and elevated testosterone-levels — in addition to infertility and, potentially, sterility — from unintentional self-injection.

EPA’s Fact Sheet, the manufacturer’s training, and BLM’s operating procedures fail to emphasize the magnitude of the risk — the PZP-in-question is a horse-size dose.

But Is There a Mandate to Practice Scientific Integrity?

Yes. The Department of the Interior’s (DOI) Code of Scientific and Scholarly Conduct applies to all staff members as well as to contractors, partners, permittees, and volunteers. The Code states: “Scholarly information considered in Departmental decision making must be robust, of the highest quality, and the result of as rigorous scientific and scholarly processes as can be achieved. Most importantly, it must be trustworthy.” [19]

BLM has ignored and suppressed independent scientific findings about PZP’s adverse effects and unintended consequences. Instead, BLM continues to rely almost exclusively on the manufacturer’s claims — shown and known to be false — regarding PZP’s safety for use on horses and for handling by humans. BLM is thus non-compliant with the Policy and malfeasant in its responsibilities to protect staff, volunteers, and the wild horses under its jurisdiction. BLM is also misleading and disinforming Congress and the American public about the PZP pesticide.

The manufacturer of PZP — a partner to BLM — misrepresented the pesticide as safe for use on animals by humans. The manufacturer knew or should have known that the former hypothesis regarding PZP’s mode-of-action had been disproved, and that PZP has dangerous side effects, safety-issues, and unintended consequences. Yet he hid and denied that information and failed to warn about PZP’s adverse effects. The manufacturer cited his own research as if it were definitive, and aggressively criticized independent researchers whose findings did not fully support his claims. Indeed, he recently submitted an Op-ed to The Salt Lake Tribune wherein he belittled the research of fellow scientists whose studies on PZP yielded results somewhat different from his own. [8] His accusations were so unreasonable that the scientists felt it necessary to submit an Op-ed in response to defend the integrity and validity of their work. [11] The manufacturer also disparaged members of the public — one of whom was a member of the Pennsylvania Game Commission — who expressed concerns about PZP. He dismissively accused them of “an attempt to mislead,” of “hyperbole,” of “knowingly manipulating information,” of “attempts to frighten people,” and of indulging in an “anti-intellectual approach to debates.” [7] By these actions, the manufacturer violated the DOI’s Code of Scientific and Scholarly Conduct.

PZP Manufacturer Misled Trainees into Believing that PZP Was Safe

BLM staff and volunteers receive their training from PZP’s manufacturer in how to handle and administer the pesticide. BLM is remiss in delegating the training to the manufacturer without verifying the adequacy of the instruction and the truthfulness of it. Two comments recorded recently in the media suggest that PZP’s manufacturer misled not just the public-at-large but those who received training therefrom in how to administer PZP.

First, the manufacturer has been quoted as saying that PZP is “so safe it is boring.” [3] Independent research shows otherwise — that PZP is a powerful hormone disruptor that could sterilize a female with just one injection. If trainees believe that PZP is boringly safe, they will be less likely to protect themselves adequately from this dangerous pesticide. Indeed, many of the trainees are women and, therefore, particularly at risk. Likewise, wild-horse advocates are lulled into complacency, trusting that PZP is harmless to the Pryor Mountain horses and their rare genetic alleles. Of course, none of that is true.

Second, a PZP supporter, who self-identified as a recent completer of the PZP-darting training program conducted by the manufacturer, said in a comment posted to a news article: “I just received my FDA certification to handle and administer Native PZP. Would you be so kind to provide a link to the study you keep referencing? To my knowledge, and those teaching the Native PZP certification class, there are no side effects of the PZP produced by Dr. Kirkpatrick and his team, which is Native PZP.” [2] Key words: “no side effects.” It is disturbing that a person who was, no doubt, motivated by a desire to help the horses has been disinformed regarding PZP’s safety-hazards to humans as well as to horses.

BLM Fails to Maintain Proper Supervision of the PZP Volunteers

The issue of safety is not the only concern. As BLM has admitted, volunteers darted the wrong mares on Pryor Mountain. These errors evidence that BLM has failed to maintain supervisory control over the volunteer-inoculators, allowing them to conduct the PZP-darting by themselves. The mistakes further evidence that the volunteers do not understand what is expected of them. Who can say whether other procedures were not complied with either. The fact that mares were darted who were ineligible for PZP per the then-current protocol, but who would be eligible under the proposed-but-not-yet-promulgated new “prescription,” suggests that the volunteers may have concluded — from BLM’s open contempt for the Constitution and disrespect for the NEPA process — that was okay for them to start darting otherwise-ineligible mares right away. Not surprisingly, BLM blames the volunteers for these mistakes, but probably has not informed them that they are being made to take the rap for management’s shortcomings.

Conclusions

PZP is appropriately categorized as a pesticide by the EPA. PZP “works” by tricking the immune system into attacking and destroying the ovaries. PZP has many adverse effects as well as unintended consequences. PZP presents safety-hazards to humans who handle it. PZP is a dangerous pesticide whose use is antithetical to the spirit and intent of the Wild and Free-Roaming Horses and Burros Act. BLM’s continuing to use PZP while ignoring and suppressing the evidence of its harmful effects constitutes malfeasance.

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This report was completed by Marybeth Devlin on December 24, 2015. Copyright Marybeth Devlin and Protect Mustangs 2015.

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References:
1. EquiMed staff. (2010, March 13) Equine Reproductive Maturity in Mares and Stallions. Puberty in Equines. Retrieved from http://equimed.com/health-centers/reproductive-care/articles/equine-reproductive-maturity-in-mares-and-stallions

2. EWCS. (2015, November 10). Re: “Contraceptive could reduce taxpayer costs for wild horses.” Retrieved from http://wyomingpublicmedia.org/post/contraceptive-could-reduce-taxpayer-costs-wild-horses#comment-2352628323

3. Ferguson, Mike. (2015, June 4) “Police called as group protests wild horse contraceptives.” The Billings Gazette. Retrieved from http://billingsgazette.com/news/state-and-regional/montana/police-called-as-group-protests-wild-horse-contraceptives/article_81462303-e128-5ee8-a7ef-2c8b098450f6.html

4. Gray, M.E. and Cameron, E.Z. (2010) Does contraceptive treatment in wildlife result in side effects? A review of quantitative and anecdotal evidence. Reproduction 139, 45-55. Online publication date: 1-Jan-2010. Retrieved at http://www.reproduction-online.org/content/139/1/45.full

5. Kaur, Kiranjeet and Prabha, Vijay. (2014) “Immunocontraceptives: New Approaches to Fertility Control,” BioMed Research International, vol. 2014, Article ID 868196, 15 pages, 2014. doi:10.1155/2014/868196. Retrieved from http://downloads.hindawi.com/journals/bmri/2014/868196.pdf

6. 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

7. Kirkpatrick, Jay. 2007. “Response to PA [Pennsylvania] Game Commission.” Posted on PNC’s Wildlife Forever Home Page. Retrieved from http://www.pzpinfo.org/home.html

8. Kirkpatrick, Jay F. (2015, May 16). Op-ed: Wild-horse contraceptives are based on sound science. The Salt Lake Tribune. Retrieved from http://www.sltrib.com/opinion/2517266-155/op-ed-wild-horse-contraceptives-are-based-on?fullpage=1

9. Knight, Colleen M., Rubenstein, Daniel I. 2014. The Effects of Porcine Zona Pellucida Immunocontraception on Health and Behavior of Feral Horses (Equus caballus). Princeton University Thesis, Ecology and Evolutionary Biology. Retrieved from http://dataspace.princeton.edu/jspui/handle/88435/dsp01vt150j42p

10. Nettles, Victor F. (1997) Potential consequences and problems with wildlife contraceptives. Reproduction, Fertility and Development 9(1) 137 – 144. Retrieved from http://www.publish.csiro.au/paper/R96054.htm Accessed full pdf text via purchase of a copy from Csiro Publishing.

11. Nuñez, Cassandra, Jim Adelman and Dan Rubenstein. (2015, July 3). Op-ed: Wild horse contraception not without unintended consequences. The Salt Lake Tribune. Retrieved from http://www.sltrib.com/opinion/2653298-155/op-ed-wild-horse-contraception-not-without

12. PCOS Foundation. (2015) What Causes PCOS? Retrieved from http://www.pcosfoundation.org/what-is-pcos

13. PNC, Inc. (Pity Not Cruelty). PZP FAQs. (2006) “Frequently Asked Questions on Immunocontraception.” (Special thanks to Jay Kirkpatrick and Rick Naugle for additions and corrections). Retrieved from http://www.pzpinfo.org/pzp_faqs.html

14. Raab. Lauren. (2015, May 31) “120,000 endangered saiga antelopes die mysteriously in Kazakhstan.” Los Angeles Times. Retrieved from http://www.latimes.com/science/sciencenow/la-sci-sn-saiga-antelope-die-off-20150531-story.html

15. Ransom JI, Hobbs NT, Bruemmer J (2013) Contraception Can Lead to Trophic Asynchrony between Birth Pulse and Resources. PLoS ONE 8(1): e54972. doi:10.1371/journal.pone.0054972. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/23383018

16. Rose-Cihakova-Caturegli Laboratory. (n.d.) Autoimmune Oophoritis. Johns Hopkins Pathology. Retrieved from http://pathology.jhu.edu/department/RCCLab/Oophoritis.cfm

17. Sacco AG, Subramanian MG, Yurewicz EC. (1981) Passage of zona antibodies via placenta and milk following active immunization of female mice with porcine zonae pellucidae. J Reprod Immunol. 1981 Dec;3(6):313-22. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/7328557

18. Sussman, Karen. (2015 June 6) “Suspicious Deaths with Use of Anti-Fertility Drugs.” International Society for the Protection of Mustangs and Burros. Retrieved from http://www.ispmb.org/BirthControlDeaths.html

19. United States Department of the Interior. Integrity of Scientific and Scholarly Activities Policy. Code of Conduct. Retrieved from https://www.doi.gov/scientificintegrity

20. United States Environmental Protection Agency. Office of Chemical Safety and Pollution Prevention. Pesticide Fact Sheet. Porcine Zona Pellucida (PZP). New Chemical. Nonfood Use. January 2012. Retrieved from
http://www3.epa.gov/pesticides/chem_search/reg_actions/pending/fs_PC-176603_01-Jan-12.pdf

21. U.S. Department of Health and Human Services. National Institutes of Health. Endocrine Disruptors. Retrieved from http://www.niehs.nih.gov/health/topics/agents/endocrine/

22. U.S. National Library of Medicine. National Institutes of Health. Ovarian overproduction of androgens. Retrieved from https://www.nlm.nih.gov/medlineplus/ency/article/001165.htm

23. Varras M, Anastasiadis A, Panelos J, Balassi E, Demou A, Akrivis CH. (2013) Autoimmune oophoritis: Clinical presentation of an unusual clinical entity. OA Case Reports 2013 Jan 31;2(1):7. Retrieved from http://www.oapublishinglondon.com/article/369#

Pm PZP Darts

 

www.ProtectMustangs.org
Protect Mustangs is a nonprofit organization who protects and preserves native and wild horses.




Equine reproductive immunology Ph.D speaks out in 2010 against using PZP on wild horses

PM President Obama Listen to the Science

November 27, 2010

Jared Bybee, Wild Horse and Burro Specialist

Department of the Interior

Bureau of Land Management

Billings Field Office

5001 Southgate Drive

Billings, Montana 59101-4669

VIA FAX: 406-896-5281

RE: Pryor Mountain Wild Horse Range Fertility Control Preliminary Environmental
Assessment Tiered to the Pryor Mountain Wild Horse Range Environmental Assessment and Herd Management Area Plan May 2009 EA DOI-BLM-MT-0010-2011-0004-EA

Dear Jared Bybee:

Background

I appreciate the opportunity to submit comments on the Pryor Mountain Wild Horse Range
Fertility Control Preliminary Environmental Assessment Tiered to the Pryor Mountain Wild
Horse Range Environmental Assessment and Herd Management Area Plan May 2009 EA DOI-BLM-MT-0010-2011-0004-EA. My background is in equine reproductive immunology and wildlife conservation. I applaud the Billings Field Office of the Bureau of Land Management (BLM) for a thoughtful approach to this issue. Cover letter 4700 (010.JB) dated November 2010 and signed by James M. Sparks, Field Manager states that the BLM would consider comments and revision to the EA or unsigned FONSI as appropriate. I urge a “no action alternative” as outlined on page 7 and 8 of the EA. This request is based on two pieces of new scientific evidence about effects of current immuno-contraception use.

Porcine Zona Pellucida (PZP) Contraception

The proposed action as stated on page 7 of this EA would exempt “mares ages 5-10 unless they have produced foals, or are part of a large bloodline.” This is reminiscent of the approach taken with the Assateague Island wild horse population. It is a compromise approach to this issue, in comparison to placing all mares on PZP. However a recent study shows that mitochondrial DNA diversity is low in the Assateague Island horse herd (Eggert et al. 2010). Since mitochondrial DNA is inherited from the mother (mare), this is evidence that female inherited genetics on Assateague Island wild horses is under represented. It is imperative that this be assessed before rolling out a similar management plan for the Pryor Mountain wild horses.

There is a recent Princeton University study on PZP effects. Consecutive PZP applications, analogous to the proposed action plan in this EA, showed that mares gave birth later in the season, and were cycling into the fall months (Nunez et al. 2010). In a state like Montana where freezing temperatures are found in the fall, this can have serious and long term effects on foal survivorship.

I must include a statement on long term consecutive use of PZP. Any form of PZP contraception is not completely reversible in mares depending on the length of use of PZP. Contraception can only be reversed when the antibody titer decreases to 50-60% of the positive reference sera (Liu et al. 2005). Mares treated for 7 consecutive years do not return to viable fertility (Kirkpatrick and Turner 2002; Kirkpatrick et al. 2009). The issue of reversible contraception is very important to be able to maintain wild equines in the United States. Long term treatment with PZP has inherent negative potential for this herd.

I am requesting a new look at the proposed fertility control action for the Pryor Mountain wild horses.

Sincerely,

Christine DeCarlo, Ph.D.

Lori S. Eggert, David M. Powell, et al. (2010). “Pedigrees and the Study of the Wild Horse
Population of Assateague Island National Seashore.” Journal of Wildlife Management
74(5): 963-973.

J. F. Kirkpatrick, A. Rowan, et al. (2009). “The practical side of immunocontraception: zona
proteins and wildlife.” J Reprod Immunol 83(1-2): 151-7.

J. F. Kirkpatrick and A. Turner (2002). “Reversibility of action and safety during pregnancy of immunization against porcine zona pellucida in wild mares (Equus caballus).” Reprod
Suppl 60: 197-202.

I. K. Liu, J. W. Turner, Jr., et al. (2005). “Persistence of anti-zonae pellucidae antibodies
following a single inoculation of porcine zonae pellucidae in the domestic equine.”
Reproduction 129(2): 181-90.

Cassandra M. V. Nunez, James S. Adelman, et al. (2010). “Immunoctraception in Wild Horses (Equus caballus) Extends Reproductive Cycling Beyond the Normal Breeding Season.” PLos ONE 5(10): 1-10.

(Posted for educational purposes)

 

Science proves PZP is sterilizing wild horses

The truth

The Effects of Porcine Zona Pellucida Immunocontraception on Health and Behavior of Feral Horses (Equus caballus)

Authors: Knight, Colleen M.
Advisors: Rubenstein, Daniel I.
Department: Ecology and Evolutionary Biology

The horse population on Shackleford Banks, a barrier island off the coast of North Carolina, has been controlled using a program of porcine zona pellucida immunocontraception since 2000. Prior studies found no negative physiological effects of the immunization, but suggested some adverse effects on behavior such as increased harem switching and extended reproductive season. Although no mares were immunized in the year of study (2013), we examined the effects of past contraception and foaling on health and behavior of the mares in an attempt to better understand its impacts on both the individual and the population. Current lactation was found to be the best predictor of health and behavior: lactating mares were in worse physical condition, spent more time grazing, and switched harems fewer times. Mares that had never foaled also were in better physical condition than mares that had foaled in the past, but did not differ in behavioral measures. There were indications that the PZP treatment has had effects other than preventing pregnancy: an increased number of years since immunization was correlated with better body condition and fewer harem switches, independent of lactation. Contraception treatment intensity or timing did not have any significant adverse effects on health and behavior on its own. However, three or more consecutive years of treatment or administration of the first dose before sexual maturity may have triggered infertility in some mares. Inducing sterility, while relieving the mares from the energetic costs of lactation and reducing the stress from harem switching, may have unintended consequences on population dynamics by increasing longevity and eliminating the mares’ ability to contribute genetically.

Read more here: http://dataspace.princeton.edu/jspui/handle/88435/dsp01vt150j42p

Sign and share the urgent petition: Grant a 10-year moratorium on wild horse roundups for recovery and studies

PZP is an EPA approved restricted use pesticide and Protect Mustangs is against using it on wild mares especially when there is an underpopulation problem on public land despite government spin. The truth is most wild herds are being threatened with low numbers and a lack of genetic variability.

Controversy over PZP

nt B:W

 

Know this

Ken Salazar’s Wild Horse Plan Fuels Accusations That He’s In The Pocket Of Ranchers, Associated Press, 2010: http://www.huffingtonpost.com/2009/10/17/ken-salazars-wild-horse-p_n_324799.html

Wildlife ecologist Craig Downer of Nevada accused Salazar, a former rancher, of acting on behalf of those who view mustangs as taking scarce forage away from their cattle herds. Downer contends cattle are more destructive to the range because they concentrate in high numbers around water sources instead of grazing over a wider area as wild horses do.

“Both the Forest Service and the Bureau of Land Management have the right to remove livestock to ensure viable, healthy populations of wild horses. But they refuse to exercise that,” Downer said. “Their master is primarily these traditional ranching interests.”

Opposition grows to Salazar’s plan to move wild horses to Midwest preserves, Associated Press 2009http://www.oregonlive.com/news/index.ssf/2009/12/opposition_grows_to_salazars_p.html

Horse defenders have stepped up their efforts in recent weeks, suing to block a proposed roundup of 2,700 horses in northern Nevada and lining up the support of celebrities such as Sheryl Crow, Lily Tomlin, Bill Maher and Ed Harris.

Crow took her concerns directly to Salazar in a telephone call this past week.

One of the first things he said was something must be done because the horses are starving. We (advocates) don’t believe it,” Crow said in an interview with The Associated Press.”

7 Preserves Envisioned to Manage Wild Horses, New York Times, 2009http://www.nytimes.com/2009/10/08/us/08horses.html?_r=0

“HELENA, Mont. — Interior Secretary Ken Salazar said Wednesday that he was proposing to create seven new wild-horse preserves, including one in the East and one in the Midwest, to address the problem of a growing population crowding the Western range.

The program, which also applies to wild burros, would expand the use of contraceptives and would geld more herds on public lands in the West, Mr. Salazar said.”

. . . ”

Yet the proposal quickly drew criticism from wild-horse advocates. Ginger Kathrens of Colorado Springs, a maker of documentary films who has chronicled the lives of a wild-horse herd in Montana, said that blocking reproduction could alter the animals’ behavior.

“It takes the wild out of wild-horse herds,” she said. “They’re families in sophisticated societies. Creating gelding herds and preventing them from reproducing is managing them toward extinction.”

But ranchers, who see wild horses as competing with cattle for grasses and water, welcomed the proposal. Jeff Eisenberg, executive director for the Public Lands Council, a group that works on public lands issues for ranchers, said Mr. Salazar’s proposal was a big step toward a solution.”

Sheryl Crow Slams Salazar’s Wild Horse Plan, Huffington Post 2010http://www.huffingtonpost.com/2009/11/22/sheryl-crow-slams-salazar_n_366809.html

With one voice we are insisting that our government stop managing these beautiful and important animals to extinction,” Crow said in a statement released by the Cloud Foundation, a Colorado Springs, Colo.-based horse advocacy group”. . .

It’s time for all of us to speak up for our wild horses and burros so we do not lose these living legends and inspiring symbols of our freedom in America,” she said.

Madeleine Pickens praises Salazar wild horse plan, Horsetalk, 2009http://www.horsetalk.co.nz/news/2009/10/077.shtml#axzz3HKN0uSuY

“Interior Secretary Ken Salazar announced wide-ranging proposals this week in which horses taken from the Western rangelands would be relocated to new preservation areas further east, utilising better quality grassland.

His plan includes the aggressive use of reproduction controls to manage numbers. Salazar hoped the new herd areas would provide tourism opportunities for nearby communities” . . .

Pickens said she would support Secretary Salazar’s efforts, and would gladly compete to offer the wild horse sanctuary that she has planned to the bureau as one of the facilities proposed by Secretary Salazar.”

 

MANAGEMENT OF WILD HORSES WITH PORCINEZONA PELLUCIDA: HISTORY, CONSEQUENCES, AND FUTURE STRATEGIES, Cassandra M.V. Nuñez, Princeton: http://bit.ly/1rJywKl

“However, recent research in other populations has revealed behavioral and physiological side effects of long-term PZP use.”

 

Injection-Site Reactions in Wild Horses (Equus caballus) Receiving an Immunocontraceptive Vaccine, By James E. Roelle and Jason I. Ransom, http://pubs.usgs.gov/sir/2009/5038/

“Abnormal dart trauma included cases where the dart hit bone or the needle broke off. We found strong evidence (odds ratio = 5.023, P = 0.001) for a higher probability of occurrence of swelling when darts were delivered by blowgun. We found some evidence (odds ratio = 8.729, P = 0.07) that abnormal dart trauma led to a higher frequency of nodule formation. Nodules were the most common reactions observed and often persisted for a year or more, but in our observations they did not appear to change any animal’s range of movement or locomotor patterns and in most cases did not appear to differ in magnitude from naturally occurring injuries or scars. We were unable to perform histological examinations of these nodules, but they may be similar to granulomas reported by other investigators following administration of Freund’s adjuvant.”

Ecologist Craig Downer speaks out against using PZP in the Pryors http://protectmustangs.org/?p=4178

Why end natural selection in the Pryors? Should humans run a wild horse breeding program or does nature know best? http://protectmustangs.org/?p=4941

The Horse and Burro as Positively Contributing Returned Natives in North America, Craig Downer  http://www.sciencepublishinggroup.com/journal/paperinfo.aspx?journalid=118&doi=10.11648/j.ajls.20140201.12 2014

Horse contraceptive study raises concerns

October 29, 2010
By Laurie Dixon
Research indicates the long-term horse contraceptive, porcine zona pellucida (PZP), extends the breeding season in wild horses, raising concerns over the social consequences of the drug on herds.

PZP, which is derived from pig eggs, is increasingly being used in wild horse herds . . .

Read more: http://www.horsetalk.co.nz/news/2010/10/220.shtml#ixzz38YJwjAdY

Alarm over behavioral and physiological side effects of wild horse birth control (PZP)

 

 

MANAGEMENT OF WILD HORSES WITH PORCINE ZONA PELLUCIDA: HISTORY, CONSEQUENCES, AND FUTURE STRATEGIES

Cassandra M.V. Nuñez

Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey

ABSTRACT

The advent of immunocontraception with porcine zona pellucida (PZP) has all but revolutionized wild horse management, providing a more humane method of population control than earlier strategies. Early studies on Assateague Island National Seashore have described it as an ideal form of fertility control in that it reduces the chance of conception to below 10%, can be delivered remotely, is reversible (after short-term use), lacks debilitating physiological side effects, cannot pass through the food chain, and shows minimal effects on social behaviors. However, recent research in other populations has revealed behavioral and physiological side effects of long-term PZP use. These results indicate that studies from one population may not necessarily be applicable to another, regardless of similarities in habitat and population structure. Careful study of the animals’ demography, physiology, and behavior is necessary prior to and during treatment to ensure that a) the potential effects of PZP can be assessed accurately, and b) within managerial constraints, PZP effects are ameliorated as much as is possible. Here I explain the history of PZP use in wild horses, its side effects on the horses of Shackleford Banks, North Carolina in comparison to other populations, and offer management suggestions based upon wild horse biology and behavioral ecology, which may minimize or prevent these side effects in other populations.

Read the full article here: PM Nunez 2010 management of horses with PZP

 

Posted for educational purposes only

The law was made to protect mustangs & burros so why all the abuse?

Wild horses and burros are supposed to be treated as “components of the public lands”. 16 U.S.C. § 1333(a) The law is clear that “wild free-roaming horses and burros shall be protected from capture, branding, harassment, or death” and entitled to roam free on public lands where they were living at the time the Act was passed in 1971. 16 U.S.C. § 1331 These legally protected areas are known as “herd areas,” and are defined as “the geographic area identified as having been used by a herd as its habitat in 1971.” 43 C.F.R. § 4700.0-5(d).

 

The Wild Free Roaming Horse & Burro Act also authorizes designation of specific ranges for wild horses and burros. “Range’ means the amount of land necessary to sustain an existing herd or herds …and which is devoted principally but not necessarily exclusively to their welfare in keeping with the multiple-use management concept for the public lands”. 16 USCS §§ 1332(c), 1333(a). ~Animal Law Coalition

 

 

Why is the Bureau of Land Management (BLM),–the agency responsible for the care and welfare of wild horses and burros–allowed to break the very law enacted to protect our native wildlife and heritage animals?

If you don’t like the photos taken by witness and filmmaker Stephanie Martin at the Owyhee Roundup then please meet with your senators and representatives to ask them to stop the abusive roundups.

Is there really an overpopulation problem?

It’s long overdue for an independent and accurate wild horse and burro census for each Herd Management Area (HMA). BLM’s population estimates are only that–estimates. It’s easy to count cows as horses from the air and double count horses as they roam from area to area.

If there really is an overpopulation problem then using fertility control drugs on non-viable herds or sterilizing herds will be a disaster. Why? This would ruin their gene pool and result in inbreeding. Mother nature has a ‘survival of the fittest’ program in place that ensures only the strong, healthy and wise reproduce.

Current thriving natural ecological balance studies on the range are necessary. For decades wild horses have been scapegoated for the damage created by livestock–especially to fragile riparian areas. Cattle enjoy standing in riparian areas all day whereas wild horses come for a drink and leave for the rest of a day. Princeton University has proven wild herds reverse desertification so livestock benefits from more abundant forage.

The Appropriate Management Levels (AML) for wild horses and burros were set by the Government. The Cattlemen are a wealthy lobbying force in Washington. It’s no surprise that cattle outnumbers wild horses on the range at least 50 to 1 on HMAs throughout the West.

Currently the BLM uses archaic methods of range management which allow livestock grazing methods that are harsh on the land, a wide use of pesticides and extraction industry pollution. The range is being destroyed. Removing wild horses is the wrong action because the native equids can heal the range and reverse desertification.

What’s wrong with roundups

Helicopter roundups are harsh on the environment. Chasing wild horses creates unnatural stampedes zigzagging over 10-15 mile areas many times per day for many weeks. This ruins the high desert environment and disturbs species such as the sage grouse.

Rounding up more federally protected native wild horses than they can adopt out fails as a management technique. Wild horses and burros end up stockpiled in holding facilities at taxpayer expense. After the cruel roundups, wild horses loose what is most precious to them–their families and their freedom.

Solutions

Using Range Design, which includes Allan Savory’s Holistic Rangeland Management, is a viable solution for today’s range issues. More wild horses and burros should be allowed on the range to reverse desertification, reduce fuel for wildfires and create biodiversity. This ultimately improves rangeland grazing for livestock.

“Holistic Management using native wild horses, heritage burros and livestock should be used for rangeland programs across the West,” explains Anne Novak, executive director of Protect Mustangs. “It’s a win-win that works to heal the land, reverse desertification and reduce global warming”

Wildlife and cows can be partners, not enemies, in search for food

Cross-posted from News at Princeton

Princeton University researchers are leading an effort to put to pasture the long-held convention of cattle ranching that wild animals compete with cows for food.

Two recently published papers — including one in the journal Science — offer the first experimental evidence that allowing cattle to graze on the same land as wild animals can result in healthier, meatier bovines by enhancing the cows’ diet. The findings suggest a new approach to raising cattle that could help spare wildlife from encroaching ranches, and produce more market-ready cows in less time.

The reports stem from large-scale studies conducted in Kenya wherein cows shared grazing land with donkeys in one study and, for the other, grazed with a variety of wild herbivorous animals, including zebras, buffalo and elephants. The lead author on both papers was Wilfred Odadi, a postdoctoral research associate in the lab of Dan Rubenstein, the Class of 1877 Professor of Zoology and chair of Princeton’s Department of Ecology and Evolutionary Biology.

In August, Rubenstein and Odadi reported in the journalEvolutionary Ecology Research that cattle paired with donkeys gained 60 percent more weight than those left to graze only with other cows. The researchers proposed that the donkeys — which were chosen as tamer stand-ins for zebras and other wild horses — ate the rough upper-portion of grass that cows have difficulty digesting, leaving behind the lush lower vegetation on which cattle thrive.

Donkey Cow in field

In August, the Princeton researchers reported in the journal Evolutionary Ecology Research that cattle paired with donkeys gained 60 percent more weight than those left to graze only with other cows. The researchers proposed that the donkeys — which were chosen as tamer stand-ins for zebras and other wild horses — ate the rough upper-portion of grass that cows have difficulty digesting, leaving behind the lush lower vegetation. (Photo by Dan Rubenstein)

In September, Odadi and his co-authors on the Science paper reported that other grazers, especially zebras, did remove the dead-stem grass layer and that cattle indeed seemed to benefit from sharing land with wild animals. Cows in mixed grazing pastures took in a more nutritious diet and experienced greater daily weight gain — but this effect was limited to the wet season, the length of which can vary by region. Cattle competed with wild species for food in the dry months.

Nonetheless, the Princeton studies help counter an enduring perception that wildlife is an inherent threat to the food supply of livestock, Rubenstein explained. These results could prove crucial to preserving animals that are increasingly threatened as the human demand for food drives the expansion of land used to raise cattle. Zebras and wild horses are especially vulnerable to the spread of pastures because of their abundance.

“Grazing competition from other animals has been an issue throughout history,” Rubenstein said.

“There’s a fear that if some other animal is eating grass meant for livestock, that hurts the rancher. Those perceived competitors were seen as vermin and exterminated,” he said. “These experiments suggest that in certain cases cattle can actually experience considerable advantages in terms of growth when allowed to graze with other species.”

Experimental proof of old observations

The studies are the first to experimentally test and prove hypotheses from the 1960s that equines make grazing land more suitable for bovines, a dynamic known as facilitation, Rubenstein said. Observations of zebras and wildebeests had suggested that the zebras’ ability to digest grass stems exposed the leafy grass wildebeests prefer.

Animals in the horse and cattle families both process food through fermentation as microbes in the digestive system break down vegetation. In horse-like animals, this process takes place in an organ located after the stomach that is similar to the human appendix (though humans are not fermenters). For bovines, on the other hand, fermentation happens in the rumen, an organ before the stomach that produces cud, which is regurgitated for the animal to further chew.

As a result of these digestive distinctions, Rubenstein said, equines can eat the rough low-quality grass that would linger and fester in a cow’s slower, more complex gut. The bovines in turn enjoy the lush, easily digestible grass underneath the stems.

Donkey Cow weighing

For the study published in August, the researchers documented the weight changes and eating habits of the donkeys and cows for 12 weeks. Wilfred Odadi (rear, in hat), a postdoctoral research associate in Rubenstein’s lab based at Kenya’s Mpala Research Center, was lead author on both recent Princeton papers. The project stemmed from the senior thesis of Meha Jain (front left), who earned her bachelor’s degree from Princeton in 2007. (Photo by Dan Rubenstein)

Both Princeton studies showed that the presence of equines resulted in less dry-grass cover and a more nourishing diet for the cows. Although the study in Science matched cattle with other wildlife — including bovines such as buffalo — Odadi and his co-authors largely attributed the removal of the low-quality grass to zebras.

What was not expected was just how much the cattle can benefit, Rubenstein said.

“Scientists had this intuitively pleasing, circumstantial evidence that equines make the landscape more habitable to bovines, but the idea was never tested,” Rubenstein said. “This was the first demonstration that the animals behave accordingly, but also that the performance of the cows as measured by growth is actually enhanced. Previous evidence of the effects we found on the health and development of cattle had been missing.”

Cows versus donkeys

Rubenstein conducted the experiment reported in Evolutionary Ecology Research on rangeland in northern Kenya with Odadi, who is based at Kenya’s Mpala Research Center — with which Princeton is a partner — and co-author Meha Jain, who earned her bachelor’s degree from Princeton in 2007 and whose senior thesis was the basis of the project.

The team chose donkeys as surrogates for zebras, which suffer from food and habitat loss due to cattle operations, particularly the endangered Grévy’s zebra. Because donkeys are tame, the researchers could more easily observe, weigh and record the diet quality and health of the individual animals, Rubenstein said.

The researchers constructed six separate grazing areas divided into three high-density and three low-density pastures. Both the high- and low-density areas hosted an all-bovid group of 15 cows; an all-equid group of 10 donkeys; and a mixed group of 15 cows and 10 donkeys, for a total 60 cows and 40 donkeys. The animals grazed seven hours each day.

For 12 weeks, the researchers documented the animals’ weight changes and eating habits. In addition, the excrement of tagged cows in each grazing area was analyzed for protein, parasite and digested-grass content. Study co-authors and ecologists Herbert Prins and Sipke Van Wieren of Wageningen University in the Netherlands validated the effectiveness of these measurements.

At the end of the experiment, cows that fed alongside donkeys had beefed up by an average of 64 pounds (29 kilograms) per animal in the low-density pasture, and slightly less than 37 pounds (17 kilograms) for the high-density group. In comparison, cattle dining only with their own put on an average of 55 pounds (25 kilograms) per cow with more room to roam and only nearly 28 pounds (12.6 kilograms) in tighter confines.

When compared to the weight of the cattle recorded at the experiment’s outset, cows grazing with donkeys gained an average of 60 percent more weight than cows that did not, the authors reported. Moreover, none of the cows in the mixed groups remained at the same weight or lost weight, unlike some of the cows in the bovid-only pastures. Analysis of the protein and grass-remnant content of the cows’ dung showed that the animals consumed a healthier diet when sharing land with donkeys.

A notable feature of the study Odadi conducted with Rubenstein is that it provides some understanding of how the other animals respond to grazing with cattle, Odadi said.

The donkeys did not exhibit the benefits of intermingling to the extent the researchers observed in cattle. Donkeys grazing with cattle gained only 51 percent more weight than donkeys that did not, and dung analysis showed the donkeys in the mixed groups actually took in a less digestible diet.

But the dung of donkeys in the mixed groups also contained lower levels of parasitic worm eggs, possibly due to the cattle taking in some of the parasites during grazing, Rubenstein said. As a result, parasite infection was less debilitating in these donkeys.

Where the wild things are

For the second study, Odadi and his co-authors on the Science report changed the project’s scope to include large, wild herbivores that share the African savanna with cattle: Grévy’s zebras, African buffalos, elands, hartebeests, gazelles, elephants and giraffes. Odadi worked with ecology professor Truman Young of the University of California-Davis; Moses Karachi of Egerton University in Kenya; and Shaukat Abdulrazak, chief executive officer of the National Council for Science and Technology in Kenya.

The researchers created nine grazing areas of equal size, each with four cows. The pastures fell into three categories: cows only; plots open to medium-sized herbivores and closed to elephants and giraffes; and plots open to all wild herbivores. Each variety was randomly assigned to three grazing areas.

The experiment consisted of two 16-week trials (conducted a year apart) with each trial beginning in the dry season and ending during the wet season. In each trial, the team weighed the cows and examined the animals’ excrement to determine diet quality.

In the wet season, cattle that ate with wild herbivores took in a more nutritious diet and experienced greater weight gain than cows that did not, according to the Science report. In the cow-only enclosures, each animal put on roughly a half-pound (0.25 kilograms) each day. In the other pastures, each cow bulked up by three-fourths of a pound (0.35 kilograms) daily. The experiment coincided with 18 weeks of Kenya’s wet season. For that period, daily weight gain translated to 69 pounds (31.5 kilograms) for each animal in the cow-only enclosures, versus 97 pounds (44 kilograms) per cow in the other areas.

The dry season and resulting scarcity of grass turned that dynamic on its head, however, as Odadi and his co-authors expected. Cows grazing without other animals gained more than a half-pound per day. Weight gain for cows in the mixed enclosures plummeted to roughly one-third of a pound each day. A future direction of the project may be to determine if adjusting cattle-to-wildlife density based on the season would reduce competition when food is scarce, Odadi said.

Taking it back to the ranch

The Princeton researchers make an important contribution to the study of how to reconcile the demand for grazing land with ecosystem conservation, said Michael Coughenour, a senior research scientist at the Colorado State University Natural Resource Ecology Laboratory.

The research not only shows that facilitation between livestock and wildlife is possible, but also suggests the mechanisms — for example, the removal of dry stems — that provide that benefit, he said. Naturally, Coughenour said, many questions remain, such as if the mere presence of many grazers results in more robust plant growth, as existing research has suggested might occur.

But the results should nonetheless prompt researchers to investigate the existence of facilitation in other regions and ecosystems, as well as the livestock-to-wildlife densities that make it possible, Coughenour said. For instance, the United States and other temperate-zone countries do not have a distinct wet and dry season. Also, it cannot be assumed that grass in the American West would respond to mixed grazing in the same way as savanna grass, nor that a similar concentration of zebras and American wild horses would benefit cattle in the same way in their respective environments.

“These findings add to the dialogue by providing evidence that interactions between wild equids and livestock are not necessarily negative, as would commonly be assumed among ranchers and commercial pastoralists,” Coughenour said.

“Clearly, blanket statements that wild equids invariably compete with livestock can no longer be accepted. Facilitation is a very real possibility that should be considered and investigated,” he explained. “However, it would be equally invalid to assume that the extent and mechanisms of facilitation are universal. Research is required to clarify the relationship so as to gain a more precise understanding of the conditions under which neutral or positive interactions occur.”

In the Evolutionary Ecology Research paper, Rubenstein, Odadi and Jain delved into how the weight gain they observed in cows grazing with donkeys could translate to economic gain for ranchers by producing cattle that are ready for market sooner.

As an example, they imagined a farmer beginning with a cattle herd with an average weight of 660 pounds, or 300 kilograms, that he intends to sell after the animals put on an extra 200 pounds, or 100 kilograms. In their scenario, they first substituted the 10 donkeys in the experiment with 10 more cows to make up a herd of 25 cattle. These cows would take nearly 18 months to reach the target weight of 400 kilograms if the animals packed it on at the rate of roughly 0.2 kilograms, or a half-pound, a day, as many of the cows in the researchers’ single-species pastures did.

Replacing 10 cows with donkeys, however, would bring the remaining 15 cows to the preferred weight in about 11 months. The researchers assumed those cows would gain weight at the average of nearly 0.3 kilograms, or 0.66 pounds, a day seen in the mixed-group cows in the experiment.

“Time has a cost. If cows grow faster per day, they can get to market sooner and the landowner can preempt the costs of cattle dying from predation or disease as the animal is exposed to the elements for longer periods ,” Rubenstein said.

“From the perspective of the rancher and the people awaiting the food from his cattle, the cows develop better if there are hind-gut fermenters like zebras present,” he said. “So, by our observations, competition becomes facilitation and expands to become mutualism as both species actually benefit each other.”

Cows with a few extra kilograms of weight could be a “huge” benefit to ranchers and pastoralists, particularly in Africa, as well as to the preservation of natural lands, said Joshua Ginsberg, senior vice president for the Wildlife Conservation Society’s Global Conservation Program. Ginsberg, who received his Ph.D. from Princeton in 1988, focuses his research on conservation and animal-human interaction.

“A few kilograms is a major increase,” Ginsberg said. “If the cattle are managed well, and the markets exist and are used, it would allow for greater income, greater protein and the ability, at least in theory, to reduce cattle-stocking rates because of increased productivity.

“Many pastoralists think that zebras compete for food and this study suggests that in many circumstances, that may well not be the case,” Ginsberg said. “The authors clearly suggest that the expansion and recovery of zebra populations in lands that are focused on traditional grazing practices is potentially a benefit, rather than a cost, to these societies.”

At the Mpala Research Center, Odadi has presented his findings to local farmers, but understands the difficulty of overturning long-held views about the livestock/wildlife competition.

“The farmers we have presented these findings to are generally surprised that zebras and other wildlife can facilitate cattle,” Odadi said. “However, we have not been able to determine whether and to what extent their perception that grazing wild animals are detrimental to livestock production has actually changed.”

The first study, “Facilitation Between Bovids and Equids on an African Savanna,” was published in Evolutionary Ecology Research in August 2011, and supported by grants from the National Science Foundation, the Keller Family Trust and Wageningen University, the Netherlands.

The second study, “African Wild Ungulates Compete With or Facilitate Cattle Depending on Season,” was published in Science on Sept. 23, 2011, and supported by grants from the National Geographic Society, the National Science Foundation, the U.S. Fish and Wildlife Service, and the International Foundation for Science.