Cage Density Control and Weaning Activity

Standard mouse caging is designed to meet NIH Guide for the Care and Use of Laboratory Animals. In meeting this requirement, CLAC allows the housing maximum of: five mice weighing 15-25 grams per cage, or no more than one adult pair and a litter which is less than weaning age, or when mice are harem bred, there should be no more than one male and four females in a cage. Pregnant females should be segregated prior to delivery to avoid multiple litters in one cage. Cages that exceed the above limitations are considered overcrowded.

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WEANING ACTIVITY

Generally, mice should be weaned at twenty-one days of age, assuming that the pups are mature enough to be able to reach food and water on their own. Exceptions can be made for any pups that are too small to eat regular chow or reach the sipper tube or who may have health issues that require staying with their dam past 21 days. CLAC staff will place a dated "Please Wean" card on cages with pups at 21 days of age or at a point where, in their professional judgement, they feel the litter is ready to wean. The appearance of the "Please Wean" card is the only notification to be provided. Research personnel are expected to closely monitor breeding cages and wean offspring within the 5 days from the point the "Please Wean" card is displayed. After the 5^th day, or in case of an urgent situation, WeaningByStaff and the PI will be charged for this activity. Exemptions to this policy should be discussed with CLAC and may require submission, review and approval by the Animal Care Committee on a case by case basis.

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BREEDING CAGE DENSITIES

Where harem breeding has been set up, the Animal Care Technician will identify cages housing mice needing to be separated out when it becomes evident that the birth of a litter is imminent, by mounting a dated "Please Separate" card behind the standard cage card. From this point, the research staff has 5 days in which to remove the soon to be mom to another cage. The appearance of the "Please Separate" card is the only notification to be provided. After the 5"' day, or in case of an urgent situation, CLAC staff will separate out the pregnant animal, or, if born, the mom and litter, and the PI will be charged for this activity. Exemptions to this policy should be discussed with CLAC and may require submission, review and approval by the Animal Care Committee on a case by case basis.

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ABOUT THE AVAILABILITY OF CLEAN CAGING

Clean caging will be available on "investigator racks" which are staged in the hallways within every barrier floor. Animal Care Technicians determine the on hand cage inventory needed partially based on their expectations on research staff separating/ weaning their animals in a timely fashion. CLAC acknowledges the frustration that has sometimes been expressed when caging is no longer available on the research staff's schedule, which may not have coincided with the time frame listed in our standard procedures. Nor can CLAC predict when there will be a "run" on caging due to other research activities, especially when this occurs after regular business hours. Furthermore, sometimes caging identified as specifically reserved for an investigator is nevertheless taken by unknown others. CLAC has always suggested that research staff check the availability of investigator caging staged on barrier floors just prior to weaning/ separating activities, as well as providing CLAC with 24 hours advanced notice for requesting large quantities of caging.

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