Basic Animal husbandry for maintenance and breeding of your transgenic founder or ES cell chimeric mice:
1.Transgenic founders should be individually backcrossed to an inbred strain or outbred strain of choice. Do NOT intercross different founders, since each founder results from a separate transgene integration event.
Male ES cell chimeras should be backcrossed to the inbred strain of choice, often C57BL/6. Males that are 25%-100% chimeric based on agouti coat color should be tested.
2. Male mice must be housed one per cage or they will fight. If you want to carefully time the mating, females (one to three) can be added to the male’s cage every evening and then checked for the presence of a vaginal plug early each morning and removed to a new cage. Mice are born 19-21 days after vaginal plug detection (i.e. successful mating).
3. Alternatively, females (one to two) can be kept with the male as a family. If the male is kept continuously with the females, they will often not cannibalize the young, and will usually mate again at the time of the birth of the young. In this case, pups should be weaned promptly at three weeks to keep the newborn pups from being trampled by the older litter. If you do not check plugs each morning (the plugs dissolve after several hours), pregnancy can be detected at about 13 days by the swelling of the mother’s abdomen or an increase in the weight of the female.
4. DO NOT touch neonates with bare hands, as the scent may cause the mother to abandon the litter.
5. If neonates do not show white stomach (milk) 24 hours after birth, the mother may be bad. The pups must be cross-fostered to a lactating female or the pups will die.
6. Litters should be weaned (separated from the mother) at 3 weeks.
7. Sexual maturity of the females is approximately 6 weeks; of the males is approx. 8 weeks. Males should be housed individually starting at 5-6 weeks, as they can become aggressive and may kill one another. They must be housed individually after mating.
8. Watch for water bottle leaks; neglected wet cages can result in the death of the animals.
9. Contact the Center for Comparative Medicine staff for animal health problems in your colony or other information.