Horses can not be tamed, even when force tamed with commands, and a saddle is put on, they do not move. Horses that are not fully grown have strange behavior, like instantly growing to full when given food. This also happened in the previous snapshots before, but 15w44a is the most recent snapshot.
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Thank you for your report.
However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-89924. You can find or add further information on that report.
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