A U.S. government program designed to save animals has turned out to be a horse of a different color.

Every year, the U.S. Bureau of Land Management (BLM) rounds up between 5,000 and 10,000 wild horses and burros that live on public lands in the West. It then sells them through a special Adopt a Horse (or burro) program. The program was started as a humane way to keep wild herds from getting too large and overgrazing the land where they live.

But recent studies found that many of the adopted horses and burros did not wind up in happy pastures. Instead, people who adopted them sold them to slaughterhouses. (Horse meat can be sold to countries such as France and Belgium for up to 80 cents a pound.) The BLM says that the problem is not widespread. But one study found that the agency had lost track of 32,000 horses and burros.

Technology may help end the problem of horse and burro overpopulation: Scientists are working on a birth-control drug to keep their populations under control.