This is a synopsis of a presentation to veterinarians during The American Mustang session at the 2014 American Association of Equine Practitioners Convention, held Dec. 6-10 in Salt Lake City, Utah.

Feral tribal horses walk the streets within the Navajo Nation. They’re outside restaurants. In people’s yards. There are just too many horses, and the Navajo government is working to change that. It started in 2013 with community roundups and a veterinary management program.

Scott Bender, DVM, works as tribal veterinarian with the Navajo Nation Veterinary Program and is a USDA Animal and Plant Health Inspection Service consulting veterinarian. At the 2014 American Association of Equine Practitioners Convention, held Dec. 6-10 in Salt Lake City, Utah, Bender shared the challenges faced when managing feral horses within the Navajo Nation and results of tribal equine population management efforts.

The Navajo Nation is located in the southwestern United States, with territory spanning Arizona, Utah, and New Mexico. The reservation comprises 18 million acres and, said Bender, an estimated 75,000 to 96,000 horses. The tribe permits 12,000 livestock owners, with the majority of permit holders having one to five privately owned horses. Under tribal law, all unbranded horses within the Navajo Nation are tribal property, Bender explained. That leaves the tribe with a lot of horses.

The Navajo traditionally view horses as sport, working, and food animals. “The horse is sacred to the Navajo, but that doesn’t mean we don’t eat them," Bender explained. The Navajo believe horsemeat has medicinal, healing properties and is useful as a “winter” meat, he said, explaining that “horsemeat, by tradition, can only be eaten in the winter between October and April—end of thunder and not after ‘first thunder.’”

Initially and into the early 20th Century, the U.S. Bureau of Indian Affairs managed tribal livestock, but management has slowly transitioned to the sovereign nation government, Bender said. This happened partly because of U.S. government-approved reduction of livestock in the 1930s and the euthanasia and burial of more than 500 horses by federal authorizes following a dourine outbreak at the Canyon de Chelly National Monument, which is located in northeastern Arizona within the Navajo Nation boundaries. “This ‘waste of resources’ has left a negative indelible mark on the attitude of Navajo livestock owners toward the U.S. government,” Bender said.

To the Navajo, unused horsemeat is a wasted resource that the creator gave the people, he clarified.

With this in mind, surplus Navajo horses had historically been sold off-reservation to slaughter as a way to manage populations and produce income. When U.S. equine slaughter plants closed in 2007, the tribal horses lost 95% of their value and the surplus feral horses were left to breed without human controls, Bender said. “The current (tribal) horse issue is a direct result of the elimination of an outlet for surplus horses,” he added.

As herds grew, damage to rangelands increased, as did horse-caused human injuries. “Horses in right-of-ways caused car wrecks, human injuries, and even deaths,” Bender said. These issues led tribal communities to request that the Navajo National Department of Agriculture start its equine population management program in 2013, which involved roundups and veterinary services, including free:

Stallion and colt castrations;

Mare fertility control via porcine zona pellucida (PZP) vaccination;

Deworming for all castrated or fertility-control-vaccinated horses;

Five-way vaccination against tetanus, Eastern and Western encephalomyelitis, equine herpesvirus, and equine influenza; and

Microchip placement (since 2006, the tribe has mandated microchips, which are placed in the nuchal ligament along the neck so as not to taint the horse’s meat should it be sold or eaten, Bender said; the Navajo Nation has microchipped more than 18,000 horses since 1997).

While the initial fertility vaccination was effective, Bender described owner booster rates of horses as “dismal,” despite the program’s outreach and communications efforts promoting boosters. The program’s leadership is now investigating anti-gonadotropin-releasing hormone vaccine (know more commonly as anti-GnRH or GonaCon) use as a longer-activing and single-dose alternative to PZP.

In 2013 the Navajo Nation local communities, with the help of the Navajo Nation Departments of Agriculture and Resource Enforcement, rounded up more than 8,900 horses. Permitted owners claimed approximately 250 horses, with the tribe selling the rest with the requirement that they could not be returned to the Navajo Nation.

The veterinary program’s goal was to castrate 1,000 male horses and vaccinate 1,500 mares against fertility by the end of 2014. To date, more than 700 horses have been castrated or vaccinated with PZP for fertility control. Bender said members of communities where horse removals took place have reported improved forage conditions in spite of the continuing 14 years of drought in the southwestern United States and Navajo Nation.