The number of Americans who own horses has increased to about 9 million from about 6 million a decade ago, The Los Angeles Times reported Sunday. The increase was caused in part by baby boomers wanting to retire to a ranch lifestyle, and advances in horse breeding that made horses more numerous and affordable.

But drought has caused the price of hay to skyrocket, and that has made feeding horses an expensive proposition -- especially for the roughly one-third of U.S. horse owners who have incomes less than $50,000 per year.

Some owners turn horses over to sanctuaries, or sell their horses at bottom dollar on Web sites, the Times reported. The United States has banned horse slaughterhouses but some horses are still transported to slaughterhouses in Canada and Mexico, where they may be killed less humanely than they were before the ban, the newspaper said.

But many owners who cannot afford the $200 or more that veterinarians charge to put down and dispose of a horse, simply leave their horses to wander barren pastures and back roads until they die of starvation.