Colony Planning
It's important to determine the number of breeding pairs you need to supply sufficient mice for your experiments. The Breeding Colony Size Planning Worksheet (pdf) is a very useful resource.
Mating combinations
- Mating pair- one male, one female; common for strains with good fecundity. Leave pair together continuously, whenever possible, to maximize production.
- Mating trio- one male, two females; maximizes cage space for breeding and mothers assist in raising each other’s pups. Leave trio together continuously, whenever possible.
- Male rotation- single male placed with 1-2 female(s) per week; useful to quickly establish a colony. Once male is removed, do not return until pups are weaned.
Reproductive characteristics
Mating age: 6-8 weeks of age
Gestation: ~19-21 days
Wean age: ~21 days; up to 28 days if preferred
Litter size: 2-12 pups; highly strain-dependent
Replace breeders: ~7-8 months of age (several mutant strains have considerably shorter windows of optimal breeding performance)
How to select appropriate breeding schemes
Homozygous mutant (-/-) x homozygous mutant (-/-):
- Can be used if both sexes are viable and fertile as homozygotes
- Offspring: 100% homozygous; genotyping not required
- Controls: see Considerations for choosing controls
Heterozygous mutant (-/+) x homozygous mutant (-/-)
- Can be used if only one sex is viable and fertile as a homozygote
- Offspring: 50% homozygous; 50% heterozygous; genotyping needed
- Controls: see Considerations for choosing controls
Heterozygous mutant (-/+) x heterozygous mutant (-/+)
- Must be used if neither sex is viable or fertile as homozygotes
- Offspring: 25% homozygous; 50% heterozygous; 25% wildtype; genotyping probably required
- Controls: see Considerations for choosing controls
Timed Pregnant Females
How many breeding pairs should I obtain to start my own colony?
A minimum of two to four breeding pairs are recommended for most strains; additional pairs are suggested for strains challenging to breed, or to expedite colony expansion. Alternatively, it may be more cost-effective to have JAX provide study-ready mice for your experiments (see JAX® Breeding and Phenotyping Services).
What breeding information is available for JAX® Mice?
Consult the JAX® Mice datasheet for your strain of interest. Breeding performance is environment dependent; detailed baseline breeding statistics should be generated under your facility conditions.
My mice aren’t breeding well, what should I do?
See our Tips for poor breeders webpage.