Mich. Comp. Laws § 750.63

Sec. 63. Prima facie evidence of unlawful docking—The driving, working, keeping, racing or using of any unregistered docked horse or horses subsequent to 90 days after this act shall take effect shall be deemed prima facie evidence of the fact that the party driving, working, keeping, racing or using such unregistered docked horse or horses, unlawfully docked the tail of such horse or horses.