Colony planning

Determine number of breeders required to produce a cohort of mice for experiments, based on breeding scheme and strain reproductive capabilities.

You can determine the number of breeding pairs you need to supply sufficient mice for your experiments using our Breeding Colony Size Planning Worksheet (pdf).

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 for most strains

Breeding Schemes

Homozygous mutant (-/-) x homozygous mutant (-/-):

Heterozygous mutant (-/+) x homozygous mutant (-/-)

  • Can be used if only one gender 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 gender is viable or fertile as homozygotes
  • Offspring: 25% homozygous; 50% heterozygous; 25% wildtype; genotyping probably required
  • Controls:  see Considerations for Choosing Controls

Breeding scheme resources