According to a press release by Return to Freedom Sanctuary, who seems to have received money from the BLM in the past, the following groups want to use PZP on wild horses:
Alliance of Wild Horse Advocates
American Society for the Prevention of Cruelty to Animals
American Wild Horse Preservation Campaign
Animal Legal Defense Fund
Animals Voice
Animal Welfare Institute
Black Hills Wild Horse Sanctuary
Center for Animal Protection and Education
Citizens Against Equine Slaughter
The Cloud Foundation
Corolla Wild Horse Fund
Friends of a Legacy
Front Range Equine Rescue
Habitat for Horses
Hidden Valley Wild Horse Protection Fund
Horses for Life Foundation
Humane Society of the United States
Jicarilla Mustang Heritage Alliance
Least Resistance Training Concepts
Lifesavers Wild Horse Rescue
Montgomery Creek Ranch
National Mustang Association, Colorado Chapter
Oregon Wild Horse & Burro Association
Photographers for the Preservation of Wild Horses and Burros
Pine Nut Wild Horse Advocates
Respect 4 Horses
Return to Freedom Wild Horse Sanctuary and Preservation
Salt River Wild Horse Management Group
Serengeti Foundation
Southern Sun Farm Sanctuary
Steadfast Steeds
Virginia Range Wildlife Protection Association
Wild Equid League (Colorado)
Wild Horses of America Foundation
Wild Horse Connection
Wild Horse Education
Wild Horse Observers Association
Wild Horse Preservation League
Don’t let yourself be fear mongered. Read the Science Against PZP:
The Fact Sheet on PZP: http://protectmustangs.org/?p=8749
PZP is Dangerous: http://protectmustangs.org/?page_id=6922
Protect Mustangs is an organization who protects and preserves native and wild horses.