The Anti-Cow is a Passive Mob that has the ability to create liquid antimatter if used with a bucket. (in the same fashion as gathering milk form a normal Cow)

Be Aware: Much with all Anti-Mobs, with the Exemption of the Anti-Player, Contact with a normal version of the mob in question will cause a powerful explosion.

A link to a Stream Clip of the Yogscast and their encounter with an Anti-Cow:

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