From time to time, you hear about the birth of a foal in an area where the advocates are working vigorously to snuff out new life.
They usually rely on predators to take out any youngsters that slip through their darting programs but those who survive may have faulty immune systems.
PZP tricks the immune system into attacking the ovaries.
The pesticide works best (sterilizes faster) on mares with strong immune systems.
They don’t bear fruit, while the immuno-compromised females keep producing foals who inherit that trait.
A herd being treated with PZP undergoes selective breeding for weak immunity, which puts the population—what’s left of it—at risk for disease and ultimately, extinction.
RELATED: Foal-Free Friday, Advocates, Assateague and Amnesia Edition.
Western Horse Watchers Association 