Many race horses go on to have other careers as jumpers, eventers, dressage horses and trail buds, not all head for the slaughter house when done racing. I have owned and worked with many off the track TB's and love them, they have a huge following and fans who are happy to buy them, take them free and re-train them.
You can not blame the horse meat industry solely on racing. Most of the horese at auction are back yard bred horses, by your typical irresponsible breeder.
Here is a quote from a US kill buyer:
"I mop up. I clean up the mess left by morons who just have to breed their mare." - Kill buyer Manny Phelps
Below is a photo of my ex-race horse who still likes a good gallop.