Iowa Code § 189A.18: Humane slaughter practices.

Every establishment subject to the provisions of this chapter engaged in the slaughter of bovine, porcine, caprine, or ovine animals or farm deer shall slaughter all such animals in an approved humane slaughtering method. For purposes of this section, an approved humane slaughtering method shall include and be limited to slaughter by shooting, electrical shock, captive bolt, or use of carbon dioxide gas prior to the animal being shackle hoisted, thrown, cast, or cut; however, the slaughtering, handling, or other preparation of livestock in accordance with the ritual requirements of the Jewish or any other faith that prescribes and requires a method whereby slaughter becomes effected by severance of the carotid arteries with a sharp instrument is hereby designated and approved as a humane method of slaughter under the law.