Consult your institution’s Animal Care and Use Committee (ACUC) for guidelines to determine the best husbandry practices at your institution.
Obtain 2-4 breeding pairs to establish a new colony. Additional breeders can significantly reduce the time needed to expand a colony.
Combining males from different litters is only appropriate at weaning (3-4 weeks). Males combined later are likely to be aggressive and to fight, causing wounds and/or death to their male cagemates. Males shipped in separate compartments likewise should not be combined.
Mate mice early, at 6-12 weeks of age. Mice tend to gain weight and be less productive if mated later.
Replace non-productive breeders. If matings have not produced a litter within ~60 days, replace them to maximize your colony production.
Retire breeders at 7-8 months of age. Rotating mice on a regular schedule will maximize colony production.
Breeding characteristics are strain- and environment-dependent. Establish normative breeding data for each strain at your facility to detect colony changes, indentify deviations, and maximize breeding efficiency.
Genetic drift can alter strain phenotype over time. Cryopreserve your unique strains with The Jackson Laboratory and refresh inbred colonies regularly to protect against genetic drift, natural disasters, breeding errors or disease outbreaks. See our Disaster Planning for more information.
Expect seasonal changes in breeding performance. Some strains produce more litters in the spring and summer than in winter and fall.
Weather & air pressure changes can alter behavior and production. Reduced breeding performance and/or hyperactivity may coincide with changes in weather.
Hybrid mice generally breed more efficiently than inbred mice. F1 and F2 hybrids and mice with mixed genetic backgrounds display hybrid vigor, producing more, larger, and healthier litters than strains on a pure inbred background.
Anticipate changes in breeding performance when transferring a mutation (knock-out) or transgene to a new genetic background. Breeding performance and phenotype of interest can change when a new background is introduced.
Avoid selection pressure. Be careful not to choose breeders that might select against your phenotype of interest. For example, if older mice develop a phenotype that limits their life span or breeding productivity, select breeders for the next generation from early 2nd or 3rd litters. Similarly, don’t select breeders based only on good breeding performance; you may unknowingly alter your phenotype.