10 things you need to know about Pesticide PZP
1. PZP — The Pesticide: PZP is an EPA-registered pesticide manufactured from the ovaries of slaughtered pigs. Some persons argue that, because PZP does not kill the mare, it is not really a “pesticide.” Actually, PZP does kill. Stillbirths are associated with the pesticide’s use, meaning that some of its supposed contraceptive effects are actually feticidal.. In addition, over the long term, PZP weakens a herd immunologically, putting it at risk for eventual or even sudden extinction.
2. PZP — The Disproved Hypothesis: PZP’s manufacturer promoted the product as generating antibodies that “block sperm attachment.” But that marketing-hype was merely an untested hypothesis postulated three decades ago. Independent researchers found that PZP has a different effect, and many adverse effects.
3. PZP — The Actual Mode-of-Action: Behaving like a perverted vaccine, PZP tricks the mare’s immune system into making antibodies that cause ovarian dystrophy, autoimmune oophoritis, ovarian cysts, and premature ovarian failure. PZP quickly sterilizes mares that have a strong immune system but has no effect on those suffering from weak immunity. Thus, PZP both works and doesn’t work but, in the long run, selects for poor immune function. Weak immunity = weak resistance to infection, which could quickly wipe out a herd. PZP also affects the foals. If a mare is pregnant or nursing when darted, PZP antibodies are transferred to her offspring via the placenta and her milk. So, inadvertently, unborn and newborn foals receive a dose or two of the pesticide when their dams are injected.
4. PZP — The Danger to Humans: PZP is a powerful endocrine-disruptor. It causes a sharp drop in estrogen levels. Unfortunately, because the manufacturer misrepresented PZP as “so safe it is boring,” volunteer-darters have become lax in following safety-precautions. Accidental self-injection could result in severe adverse effects because the dose-in-question is sized for a horse.
5. PZP — The Year-Round Birthing-Season: A longitudinal study (Ransom et al. 2013) of three herds currently under treatment with PZP found that the the birthing-season lasts virtually year-round (341 days). Out-of-season births put the life of mares and their foals in jeopardy. Nature designed foals to be born in Spring, not year-round, and certainly not in Winter.
6. PZP — Prolonged Delay in Recovery of Fertility: Ransom et al. also found that, after suspension of PZP, it takes more than a year per each year-of-treatment before mares recover their fertility. PZP’s manufacturer conceded that it could take up to 8 years to recover fertility after just 3 consecutive years of PZP treatment.
7. PZP — Scientists Say Proceed with Caution: Ransom et al. warned: “The transient nature of … PZP can manifest into extraordinary persistence of infertility with repeated vaccinations, and ultimately can alter birth phenology in horses. This persistence … suggests caution for use in small refugia ….”
8. PZP — Contraindicated for Tiny, Isolated Herds: Several years ago, BLM convened a meeting of scientists on the topic of minimum herd-size for genetic fitness. Conclusion: “Smaller, isolated populations (<200 total census size) are particularly vulnerable ….” And that’s without PZP in the mix.
9. Slow Herd-Growth: Per independent research, wild-horse herds increase at a rate of only 5% a year; and wild-burro herds, just 2%. Such slow growth does not warrant pesticide treatments administered en masse every year. Eventual sterilization is inevitable, with extinction of the herd over the long term.
10. Predators: The right way to right-size the wild-horse population is Nature’s way — predators. But those predators — mountain lions, bears, wolves, and coyotes — are persecuted mercilessly. Wildlife Services exterminates what trophy-hunters don’t shoot. Predators help the herds by favoring survival-of-the-fittest and the best genetic adaptations. Predators are the “no-cost” solution.
by Marybeth Devlin
Wild Horse Advocate
This mare waits in the alley before being led into the chute where her age and body condition will be checked. After being treated with the PZP fertility control agent, this mare will be released back to the Owyhee HMA.
Protect Mustangs is a 501(c)3 nonprofit organization dedicated to the protection and preservation of native and wild horses. www.ProtectMustangs.org