WASHINGTON — Wild horses descended from the steeds of Spanish explorers, American Indians and the U.S. cavalry are being offered for auction at Fort Worths John Justin Arena as part of a desperate effort by a federal government that cant figure out what to do with them.The Interior Department, in roundups that outraged wild-horse advocates, has removed nearly 50,000 horses from Western rangeland and paid private ranchers to put them in corrals and pastures, largely in Kansas and Oklahoma.More of Americas wild horses are now in holding facilities than in the wild.The Bureau of Land Management says the roundups are needed because the swelling horse populations are too much for the wild range to sustain. Wild-horse advocates counter that its really about favoring the interests of ranchers whose cattle and sheep graze on public land.Everyone agrees that the situation cant go on.The Bureau of Land Management is running out of space in the holding facilities and cant find more. At the same time, the cost to taxpayers of the wild-horse and -burro program has nearly doubled in the past four years to $75 million, with more than half going to holding the animals.There is no quick fix, said Tom Gorey, a spokesman for the bureau. The options are limited because were not going to put down healthy horses for which there is no adoption demand, even though the law authorizes it.The bureau could find homes for only about 2,600 wild horses and burros last year less than half the number in 2005. Arranging adoptions has become harder with the rough economy, as horses are considered a luxury, Gorey said.Theres also a glut of cheap domesticated horses on the market since the closure of the nations last horse slaughterhouse six years ago, he said. Domesticated horses tend to be more attractive to buyers than the Interior Departments wild horses, Gorey said.The Bureau of Land Management pays the Mustang Heritage Foundation $3.75 million to train some of the wild horses and put them up for auction, a program that led to 868 adoptions last year.The foundation is holding an adoption event at the John Justin Arena at the Will Rogers Equestrian Center near downtown Fort Worth, with 150 horses going up for bid Friday and the same number Sunday.The average sale price is under $500. The foundation also auctioned off horses in Fort Worth in late April.Adoptions last year, though, represented just 5 percent of the wild horses in government-funded holding facilities. The Bureau of Land Managements wild-horse and -burro advisory board said the number of horses in holding has ballooned to the point that it threatens the health and welfare of the horses and the entire program.The board recommended removing the ovaries of mares in the field as population control. The bureau is considering it, but wild-horse advocates call the procedure cruelly invasive and unnecessary.The bureau should instead balance wild horses with livestock and use contraceptive vaccines for horses, said Suzanne Roy, campaign director of the American Wild Horse Preservation Campaign, based in Hillsborough, N.C.You have wild horses on about 11 percent of BLM land. But even on that small percent, the BLM still allocates most of the forage resources to privately owned livestock, Roy said.Youll have management areas with the annual equivalent of 1,000 cows and 100 horses, and when the horse population reaches 125, BLM says the horses are overpopulating. What we really have is an overpopulation of cattle and sheep on our public lands.A National Academy of Sciences study on the wild-horse problem is due out next month and will heavily influence the debate. Among the issues covered are population control methods and the controversial question of how the Bureau of Land Management decides on the number of horses a piece of land can sustain.But Gorey said the study wont give any easy answers.Fertility control efforts have had limited effectiveness, he said, and herds can double every four years.If the bureau cant find places for the horses, that could mean limited roundups and deterioration of the range, which is going to be unacceptable for most people that care about public lands, Gorey said.