system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5 Why a horse need to be put down if it breaks a leg

Why do they kill horses if they ever Break a leg? Can't they heal it instead?
gpt
It's a very long healing process for a complex limb. Horses put a lot of weight on that limb and they can't just lie down and heal for weeks at a time.

Horses are also fairly nervous and quite stupid. They will not take it easy. They will not like the cast. They will not stoically handle the pain. Most of the time, horses are just one little incident away from freaking out over something.

The short of it is that it's extremely hard to help a horse recover from a broken limb and it's very likely that the horse will either develop complications from a poor healing process or simply break the limb again because it doesn't know how to take it easy.

With the risk of failure being so high, it's usually not worth trying unless it's an extremely valuable horse that still has a breeding purpose that doesn't rely on it having a perfectly functional limb afterward.