How is [the koy] equal to a domestic animal? Its cheilev-fat is forbidden like the cheilev-fat of a domestic animal, but one is not liable to kares on its account; it may not be bought with maaser money for eating in Jerusalem; and it is liable to [the law of] the foreleg, the cheeks, and the maw. R' Eliezer exempts, since someone who wants to take from his fellow, the burden of proof is upon him.

In what way is [the koy] equal neither to a wild animal nor to a domestic animal? It is forbidden because of kilayim with a wild animal and with a domestic animal.  One who writes his wild animal and his domestic animal to his son has not written him the koy.  If one said: “I am a nazir [on the condition] that this is a wild animal” or “a domestic animal,” he is a nazir.  And all the rest of its ways are equal to wild animals and domestic animals; it requires shechitah-slaughtering like this and like that; and it contaminates as neveilah and as a limb from a living creature, like this and like that.