LOUISVILLE, Ky. -- The Humane Society of the United States, the largest animal protection organization in the country, with approximately 2 million members and an estimated annual budget of $24 million, is launching a drive for federal legislation to improve interstate shipment of horses bound for the slaughterhouse.

"This is a brutal, flawed system that has to be stopped," said David Wills, vice president of investigations for HSUS. "We're not going to go away on this one."

Wills said the group had conducted a yearlong investigation of abuses to horses sold at auction to horse dealers who act as agents for slaughterhouses. The animals are shipped to the meat packers on two-tiered trucks, which are designed for cattle and sheep. In addition to being too cramped for horses, the trucks transport the animals on trips lasting up to 32 and 34 hours.

"The horses arrive and stagger off the trucks, sometimes on three legs," said an undercover investigator for the humane society who would not disclose her identity. "Many of them are kicked and bruised and are bleeding. Some do not survive. In addition, they are not given feed or water on these long trips."

Wills said the Humane Society made its announcement in Louisville during Kentucky Derby Week because an estimated 10 to 15 percent of the approximately 250,000 horses slaughtered each year in this country are thoroughbreds, most sold for meat for human consumption abroad.

Many are sold to dealers right off the country's small-time tracks, Wills said. The Humane Society documented the case of broken-down thoroughbreds at Mountaineer Park in Wheeling, W.Va., sold weekly for slaughter to the Bel-Tex meat-packing company in Fort Worth, Texas. The trip from holding pens in Ohio to Texas takes 34 hours.

"The thoroughbred industry is one that showcases these animals and has the political clout to help us get this legislation passed," Wills said.

The main goals of the legislation will be to ban the double-decker trucks for horse transport, limit the number of horses per shipment, limit the distance trucks can travel and mandate that the animals be fed and watered, not only during transport, but also once they reach the slaughterhouses.