Weaning

Mouse pups should be weaned in the range of 21-28 days of age. If the pups are small and the mother is not pregnant, it is permissible to go slightly beyond this age. If the mother is pregnant with conception on the day following birth of the first litter the first litter MUST be weaned by day 21 or you will have two litters in the cage
simultaneously. This violates NIH rules on crowding of the animals and can create a situation where the older pups eat the younger pups or interfere with their care.

Transgenic facility staff will place fluorescent stickers with a date
on cages that need to be weaned. The date will be one week after the day the sticker is placed. If the mice are not weaned by the date on the sticker, Transgenic Facility staff will wean them and the investigator will be charged a fee for weaning of calculated at $14/hour. The staff person who does the weaning will note on a log sheet kept in the room how many minutes were spent weaning and then the exact cost calculated. An attempt will be made to label the cage of weaned pups in a manner comprehensible to the investigators based upon the card on the overcrowded cage, but it is clear that one is better off weaning ones own mice.

No more than 2 pregnant females should be present in a cage at any one time.