Does the front half of the horse heal?
Or the back half of the horse heal?
Or can the caster pick and choose?
If the back, does the front retain its memories of being bisected?
If the front, does the front start with a new personality from scratch (wild horse)?
Do they have to "break" it again if they want to domesticate it?
If split in the middle, and you heal both, do you end up with two horses?
What happens to the mass the horse is regenerated from?
What happens to the mass of the horse they eat?
Can they cut a small portion off, then heal that partially, to create a lump of meat only?
This is a real mindbender if you think about it too long.
I think the artist was perhaps wise to offscreen it completely. And was intentional.