Bikkurim 2:8-9

Bikkurim 2:8

A koy is a certain animal whose categorization is unclear. A koy is like a wild animal in some ways, like a domesticated animals in some ways, like both in some ways, and like neither in some ways.

Bikkurim 2:9

A koy is like a wild animal in that when it is slaughtered, the blood must be covered with dirt. A koy may not be slaughtered on yom tov and if one did slaughter it, he does not cover the blood. The forbidden fats (cheilev) of a koy convey ritual impurity like those of a wild animal but the state of the fat’s impurity is doubtful (because the koy might actually be a domesticated animal). One may not redeem a first-born donkey using a koy (because it might really be a wild animal).