Where would take a horse if it died and live in the city?(I don't own a horse.)
When a horse dies, it's either buried, burned or hauled off. Burying it is pretty common, since it only requires a backhoe. Even if you lived in town, the horse would be kept on at least an acre or two, so he'd just be buried there. Most people don't burn them anymore, but some people live so far out of the way that renting a backhoe just isn't an option, and hauling them off can get pretty expensive too. There are companies which specialize in removal of large animals. They just load it up onto a sled, pull it into a trailer and haul it away to be "rendered". Animal control doesn't handle it. It's your animal, it's your responsibility, and it's expensive.
This would be up to the city ordnance for dead animals. More than likely the animal shelter would have to come and pick the animal up as it is quite large and hard to transport.