Effects on animal wellbeing and sample quality of 2 techniques for collecting blood from the facial vein of mice.

When sampling blood from mice, several different techniques can be used, with retroorbital sinus sampling traditionally being the most common. Given the severe tissue trauma caused by retroorbital sampling, alternative methods such as the facial vein route have been developed. The aim of this study was to evaluate 2 techniques for facial vein bleeding in conscious mice to ascertain whether differences in clinical outcomes, practicability of sample collection, and hematologic parameters were apparent. Blood samples were obtained from the facial vein of 40 BALB/c mice by using either a 21-gauge needle or a lancet. Subsequently, the protocol was repeated with isoflurane-anesthetized mice sampled by using the lancet method (n = 20). Behavior immediately after sampling was observed, and sample quantity, sampling time, and time until bleeding ceased were measured. Clinical pathology data and hematoma diameter at necropsy were analyzed also. The mean sample quantity collected (approximately 0.2 mL) was comparable among methods, but sampling was much more rapid when mice were anesthetized by using isoflurane. The only other noteworthy finding was a significantly reduced number of platelets in samples from anesthetized mice. Adverse, ongoing clinical signs were rare regardless of the method used. The results revealed no significant differences in welfare implications or blood sample quality among the methods or between conscious and anesthetized mice. Therefore, any of the methods we evaluated for obtaining blood samples from the facial vein are appropriate for use in research studies.