The regulations contained in the Guide for the Care and Use of Laboratory Animals stress the importance of proper animal identification in sound research and humane animal care. The Guide, as well as a number of other sources, lists many acceptable identification methods for most common laboratory animal species.
One method of identification that has been used for rodents is toe-clipping. This method involves removal of phalangeal (toe) bones of one toe on one or more limbs. The different digits removed code the identifier.
Because toe-clipping can alter the gait or weight-bearing ability of a rodent's rear limbs, the Guide limits its use to justified instances. According to the 1996 edition, toe-clipping "should be used only when no other individual identification method is feasible and should be performed only on altricial neonates." The IACUC has adopted the following policy in accordance with these guidelines: