Tosefta for Chullin 268:6

[The laws pertaining to the priestly gifts of] "the shankbone, the cheeks, and the maw" (Deut. 18:3) apply to kilayim (the mixed-breed offspring of two kosher animals) as well as to a k'vi. Rabbi Eliezer says, as to kilayim, it applies to [the offspring of] a ewe and a goat, but as to a k'vi, the burden of proof lies with the claimant. One who slaughters for medicinal purposes, to feed idolaters, or to feed dogs is liable in the gifts. One whose slaughter renders the animal carrion, one who ripped open [or] tore loose [the gullet or windpipe], and the slaughter of an idolater are exempt from the gifts. A Kohen and an idolater that sold their animal to an Israelite to slaughter are liable in the gifts, [but if it] was slaughtered with their permission and afterwards he sold it, he is exempt from the gifts. An Israelite that sold his animal to a Kohen to slaughter is exempt from the gifts, [but if it] was slaughtered with his permission and afterwards he sold it, he is liable in the gifts.