system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why are horses who break their legs so often euthanized?
gpt
Horses are skittish, dumb, 1200 pound balls of anxiety supported by toothpick legs.

They do not handle anesthesia very well and tend to get very panicky when they wake up. This makes them very likely to re-break their leg, break a different leg, or otherwise hurt themselves.

Allowing a broken bone to heal takes a lot of time *not* using that leg. Taking the weight off of one leg puts more weight on the others, increasing the likelihood of another break or another injury. They aren't used to long periods of not standing, walking, and running, so trying to force bed rest leads to bedsores and a panicky horse that will, again, be more likely to hurt themselves.

Because they are so panicky, if the horse gets spooked its first instinct is going to be to try to run...which it can't do, because it still has a broken leg. Either it will try to put the full force of a galloping horse onto that leg and break it again, or get tripped up by some kind of cast, fall, and break something else.

And even if everything goes *perfectly*, once the leg has been broken it probably will never be able to support the same force that it did before. The horse is likely to break that leg again, leading to another round of pain and suffering.

From an economic standpoint, it is very rarely worth the hassle. People have tried to mend legs on super valuable race horses - not to get them to race again, but just to let them breed - and it never works out well. From the standpoint of the quality of life of the animal, it's more humane to euthanize them. It will be months of anxiety and trauma and pain trying to mend the leg with a very high chance of getting injured again, leading to even more trauma and pain and a longer recovery with more chances to get injured *again*, for a slim chance at successful recovery that still won't give the horse a good quality of life and a high chance of getting hurt again.