HarperCollinsPublishers, Australia, 1998, 170 pp.
Despite the title, not actually horsey as such: horses (sort of) appear later. This is the first in the trilogy, and introduces Spud, the hero. He has a very nasty accident, and is whizzed off to a futuristic laboratory where he is about to become a wheelie-bin with attachments and bio-feedback mechanisms. It does not quite work out like that, however.
The Horsehead series