On Survival Ascended, Xbox One Series X:

This thing will NOT eat ANYTHING when you get the prompt to feed it. They also begin to drain health until they WILL DIE. Every time you hit Y to feed, you will dismount and you will drain taming effectiveness.

I've tried with big & small pens and without pens. Each of them ended the same way, dead horse.

You're better off waiting until you see one with a baby and murdering the parent to claim the baby. It's the only way I was actually able to get one.

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