When you put horse armor on a horse in Minecraft: Java Edition snapshot 18w44a, the horse will vanish completely, only leaving its shadow. When you take the horse armor off, the horse will reappear.
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Asteraoth
Thank you for your report!
However, this issue is a Duplicate of MC-137563.
If you have additional information, please add it to that report.
Please search before reporting, as it's likely that one exists already.
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