Mich. Comp. Laws § 287.845

Sec. 45. All swine presented to a livestock auction or collection point licensed under Act No. 284 of the Public Acts of 1937, being sections 287.121 to 287.131 of the Michigan Compiled Laws, shall be considered to have entered interstate commerce and shall be identified prior to sorting and grouping in accordance with title 9 of the code of federal regulations, and all amendments thereafter adopted pursuant to rules promulgated by the director.