I saw a short sidebar article in the Statesman, about 11 horses abandoned in Oregon. The horses were auctioned off at between $5 and $45.
There is a glut of horses right now. Feed prices have shot up (thanks, ethanol). Apparently one of the biggest factors was the closing of the only two remaining horse slaughterhouses in the US. Used to be that the slaughterhouses paid a base price, and sold the meat to Japan and France. Once the slaughterhouses closed, excess horse capacity developed, there was nothing to keep up a base price, and the price plummeted.
Given high fuel, i.e. shipping, it's also too expensive to ship them to Canada or Mexico. So, people are just abandoning the horses, which sometimes starve to death. Talk about unintended consequences.
Given Idaho's proclivity to live and let live when it comes to animals (reference dog and cock fighting), it's a wonder that the state outlaws slaughtering horses for meat.