Carson National Forest PZP Management Project

At present the primary means of population control for wild horses in the US is roundup and removal. This method has proven both inhumane and expensive. In addition, the BLM has over 30,000 wild horses in longterm holding as a result of this method, a situation that is unacceptable from both an animal welfare as well as financial perspective. A more cost-effective, humane way to control herd sizes is the use of birth control. Sky Mountain Wild is partnered with Mt. Taylor Mustangs and the US Forest Service to pioneer the use of PZP (wildlife birth control) first in NM, then in the US. We hope this will replace roundup and removal as the primary method of wild horse population control. This project fits within our mission in promoting the humane treatment of wild horses, and is aligned with our policy of maintaining herd sizes sustainable for the horses and the range.

PZP is an immunocontraceptive derived from pig ovum, developed in 1987 and produced at the Science & Conservation Center in Billings, Montana. Mares treated with PZP produce antibodies against the vaccine. These antibodies block fertilization of their own ovum, preventing conception. PZP is injected into the muscle of mares receiving treatment, via hand injection, jab stick, or remote delivery with darts. The first treatment, given with Freund’s Modified Adjuvant (FMA), an immuno-stimulant, is followed by a booster dose with Freund’s Incomplete Adjuvant (FIA) within 2-6 weeks. Thereafter, mares may be treated once yearly to maintain immunocontraceptive effects, and the effects are reversible up to seven years of treatment. PZP must be kept frozen until use, and then mixed in the field with the adjuvant just prior to treatment. Only personnel who successfully complete training at the Science & Conservation Center can administer PZP to wild horses.

90 % efficacy
reversible
capacity for remote delivery
safe for pregnant mares
safe for mares’ health with long-term use
maintains social structures and behaviors
low cost
does not pass through the food chain

PZP is classified as an experimental drug by the FDA’s Center for Veterinary Medicine. Protocols for the use of PZP and complete data on all wild horses treated with PZP must be submitted to the Science & Conservation Center for compliance with FDA regulations.

After much work by the Carson PZP team on the PZP protocol, logistics, etc. the first mares from the Carson National Forest Jicarilla Wild Horse Territory were treated with PZP on March 11, 2009. Booster doses were administered March 30, and the horses were released back to the territory April 4. This is the first time PZP has been used in the state of New Mexico, and it is the first use by the US Forest Service in the nation. The use of PZP represents a vast shift in the management of wild horses in New Mexico, as the previous method used to control population numbers has been the round-up and removal of wild horses from their territories. The funds, labor, and supplies needed to treat these first horses were donated by the team to ensure a timely start to the project.

Dan is responsible for gathering wild horses in the Carson via bait and trap method, transporting horses to holding facilities, treating selected mares with PZP, and coordinating release of those treated.

Karen is responsible for PZP protocol and database development and management, securing and managing project funding, and treating selected mares with PZP.

Anthony is responsible for ensuring compliance with US Forest regulations, overseeing care for mares for selected for treatment during holding, and coordinating release of those treated.

The project will expand to treat 50 mares between July 2009 and July 2010, with a majority of the funding needed provided by the Thaw Charitable Trust. The team is also working with Sandia National Laboratories on technology that will increase our capacity to trap selected horses for PZP treatment and release. Forty-six previously untreated mares will be gathered, taken to holding facilities for initial and booster treatment, and released. Four mares treated earlier this year will be darted remotely in the wild horse territory.

Further expansion of the project is intended for the following years, with the goal of eliminating the need for round up and removal of wild horses from the Carson. This will allow for the most humane and safe treatment of wild horses and maintaining genetic viability of the herd, as well as significant cost savings through managing population numbers in the territory.

Patience O’Dowd, President, Wild Horse Observers’ Association – worked on implementing PZP in NM in 2003-2004

Sherry Thompson, Executive Director, Thaw Charitable Trust – providing funding for the next phase of the project.