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When Bartered Cow dies or when you discard it, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")
Bartered Cow's ability is a triggered ability, not an activated ability. It doesn't allow you to discard it or sacrifice it whenever you want; rather, you need some other way of discarding it or causing it to die.
Food is an artifact type. Even though it appears on some creatures (such as Gingerbrute), it's never a creature type.
Whatever you do, don't eat the delicious cards.
You can't sacrifice a Food token to pay multiple costs. For example, you can't sacrifice a Food token to activate its own ability and also to activate the ability of Tempting Witch.
