identification-of-pre-weanling-7-day-old-mice-with-pinna-edge-biopsies

Identification of Pre-weanling 7-Day-Old Mice with Pinna Edge Biopsies

Identification and genotyping of mice is often an essential part of many in vivo scientific studies. Several methods have been described for ...

Massachusetts General Hospital Center for Comparative Medicine

Maximizing operational efficiency while maintaining appropriate animal housing conditions is a continuous focus of research animal care programs. Our institution's longstanding approach to cage-change management included scheduled cage changes every 2 wk, with spot changes if cages met established visual criteria during the intervening period. This 2-wk plus spot changing (2WS) practice for mice housed in IVC was problematic during the COVID-19 pandemic when the need arose to minimize workload to reduce on-site staffing out of concern for employee health and possible absenteeism. With the approval of the IACUC, a spot-change-only (SCO) process was adopted, with the requirement to evaluate microenvironmental parameters under both practices to confirm acceptable equivalence. These parameters (humidity, temperature, and ammonia) were evaluated in a controlled study that found no significant difference between the 2 groups. Ammonia levels did not exceed 10 ppm in any group throughout the study. To assess operational differences between these 2 approaches, we collected cage-change data and employee feedback from facilities operating under these schemes. The SCO method required fewer cage changes than did the 2WS method (10.3% per day with 2WS and 8.4% per day with SCO). Despite this benefit, through a Plan-Do-Check-Act process that has been regularly employed at our institution, employee feedback identified important operational challenges associated with the SCO practice. The SCO approach was thus refined into a scheduled spot change (SSC) practice that builds on the SCO model by incorporating a scheduled focused cage evaluation period. Based on subsequent feedback, the SSC was found to retain the efficiency benefits afforded by the SCO model and simultaneously alleviated staff and operational concerns. This result underscores the importance of integrating staff feedback with a performance standard-based approach when assessing cage-change management.

Evaluation and Refinement of a Spot-change-only Cage Management System for Mice.

Identifying and genotyping mice prior to weaning can be useful for mouse colony management. Mice of an undesired genotype can be identified prior to weaning and removed from further study, resulting in a reduction of housing costs, and labor time. We hypothesized that a pinna edge biopsy (PEB) performed by removing a portion of its edge with scissors is a reliable method for identifying and genotyping mice on postnatal day (PND) 7 consistent with PND 21, weaned mice. The pinnae of 54 C57BL/NCrl6 mice were biopsied on PND 7, and another 54 were biopsied on PND 21. Nine pinna patterns were tested. The accuracy of pattern identification was assessed on PND 7, 14, 21, 30, and 63. The mean times were compared for performing the biopsy on PND 7 and PND 21 mice, and the average time taken to identify the patterns were determined. Weight, milk spot presence, pup rejection, morbidity, and mortality were examined at various time points. During the biopsy, bleeding of the pinna, urination, vocalization, and flinching were assessed. No significant differences were detected in DNA quality, relative DNA quantity, genotyping reliability, or body weight ( ≥ 0.05) between mice biopsied on PND 7 and PND 21. Flinching at the time of PEB was significantly higher in PND 21 mice as compared with PND 7 mice ( < 0.00001). Pinna pattern identification accuracy for mice biopsied on PND 7 and PND 21 were 96% and 98%, respectively. This study validates the use of PEB for simultaneous identification and genotyping of PND 7 mice.

Article	Year
Evaluation and Refinement of a Spot-change-only Cage Management System for Mice. Journal of the American Association for Laboratory Animal Science : JAALAS\| PubMed ID: 36328418	2022
Pinna Edge Biopsy of 7 and 21 Day Old C57BL/6 Mice as a Method for Identification and Genotyping. Journal of the American Association for Laboratory Animal Science : JAALAS\| PubMed ID: 37751962	2023

Denise Molk

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