RENO, Nev. — A federal agency is on a path to sterilize wild horses on U.S. rangeland to slow the growth of herds — a new approach condemned by mustang advocates across the West.

The U.S. Bureau of Land Management also continues to resist calls from ranchers and western Republicans to euthanize or sell for slaughter the animals overflowing holding pens so as to clear the way for more roundups.

Bureau of Land Management Deputy Director Steve Ellis delivered those messages at an emotional congressional hearing last week. He offered a glimpse of the challenges facing the agency that has been struggling with what it calls a $1 billion problem.

Highlights of the hearing included Nevada’s state veterinarian calling for the round-up and surgical sterilization of virtually every mustang in overpopulated herds, a protester who briefly interrupted with shouts denouncing “welfare ranchers” turning public lands into “feedlots,” and an Arkansas congressman whose puppy is about to get neutered.

Rep. Tom McClintock, chairman of the House Natural Resources subcommittee on public lands, took aim at those who object to euthanizing mustangs “and yet seem perfectly willing to watch them succumb to excruciating death by starvation, dehydration and disease.”

Ellis said the estimated 67,000 wild horses and burros on federal land in 10 states is 2.5 times more than the range can support. However, there’s no more room in government corals and leased pastures, where 47,000 horses cost taxpayers about $50,000 per head over their lifetime.

Ellis said the agency’s “roadmap to the future” includes contraceptive vaccines and sterilization.