Tailing Of Mice

Background: "Tailing" involves cutting a piece of tissue from the terminal end of the tail for the purpose of obtaining a small tissue sample for laboratory determinations of the genetic characteristics of mouse stocks or lines. People have routinely performed this procedure without anesthesia when less than 5 mm of tissue is removed, particularly in young mice (less than four weeks of age), where anesthetic risk is higher and direct observation suggests that pain is minimal. Experience suggests that taking such tissue samples in older animals may be painful. Less invasive techniques have been reported that might offer more humane alternatives. For example, genetic characterization has been accomplished using small tissue samples from ear punching or the cells present in very small saliva samples.

Policy: "Tailing" of mice may be permitted if investigators demonstrate that less invasive alternatives (ear punch, buccal mucosa, etc.) are unsuitable and if ACC approval is obtained. Under these circumstances, tailing may be performed in mice without anesthesia provided that they are no older than four weeks of age and that no more than 5 mm. of tissue is removed. Tailing mice older than four weeks of age or removal of more than 5 mm. of tissue should be performed under appropriate anesthesia (e.g., ketamine/xylazine, metofane, etc.). If required, mice may be tailed a second time but not at an interval of less than one week from the first biopsy and anesthesia must be used. A procedure must be described in protocols about how bleeding is to be controlled that follows tailing. Obtaining samples by removing digits is unacceptable.