Mouse Breeding Systems

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Mouse Breeding Systems

• General Mouse Information
• Factors That Influence Breeding
• Breeding Systems
• Record Keeping

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General Mouse Information

• Average lifespan is 2 years
• Breeding life is 8 months
• Reach sexual maturity at 28-42 days of age
• Breeding onset
• Females 6-8 weeks Males 8-10 weeks
• Gestation is 19-21 days
• Litter size 2-16 pups per litter
• Breeding retirement
• After having 5-6 litters or 6-8 months of age

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Factors That Influence Breeding Production

• Strain
• Age
• Health
• Technician
• Temperature
• Humidity
• Lighting

• Diet
• Water
• Nesting Material
• Number of mice
• Age Bred
• Disturbances

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Inbreeding

• Homozygous animals
• Inbred strains are desirable due to their high
  degree of homogeneity
• A strain is considered to be inbred after 20
  consecutive generations of brother/sister matings

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Line Breeding

• Homozygous animals
• More intensive form of inbreeding
• Animals must have common ancestor in order to be
  bred to each other

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Outbreeding

• Heterozygous animals
• Desirable due to their high degree of individual
  diversity
• Maintained by random matings. Usually a planned
  breeding scheme that ensures that only unrelated
  animals are bred
• Usually have bigger litters with stronger, larger
  pups than litters of inbred strains

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Breeding Systems

• Monogamous
• Polygamous
• Timed
• Observed

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MonogamousOne male continuously bred to one
female.

• Pros
• Ease of accurate record keeping
• Uses postpartum estrus
• Parents are known
• Dont have to separate mice
• Little male burnout
• Exact date of birth for each litter
• Maximum number of litters per female during her
  life span

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MonogamousOne male continuously bred to one
female

• Cons
• Higher number of males required
• Higher number of cages
• If one of the breeders in an inbred strain dies
  it can be difficult, if not impossible to replace
• If the male is aggressive he may cannibalize pups
  and possibly injure the female

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Polygamous, AKA Harem BreedingOne male bred to
multiple females

• Pros
• Requires fewer males
• Fewer number of cages needed
• Can reduce exposure of pups and females to male
  aggression
• Good way to get large number of litters quickly

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Polygamous, AKA Harem BreedingOne male bred to
multiple females.

• Cons
• Higher level of technician responsibility
• Fewer litters per female
• Higher male burnout than monogamous breeding
• Can be labor intensive
• Accurate record keeping more difficult
• May not be sure who the mother is
• More than one litter can be born in a pan
• May loose postpartum estrus breeding

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Trios

• Often left together
• Co-parenting
• Can mix females
• Can help conception rates
• Watch for overcrowding
• Can be hard to determine maternal lineage of pups

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Timed Matings

• Mice are bred for a specified period
• Predictable litter due date
• Stage of pregnancy
• Gestational age of pups
• Does not require checking for plugs
• Less labor intensive than observed mating

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Observed Matings

• Female is bred to male. The next day begin
  checking for vaginal plugs
• Females are separated from the male once a plug
  is found
• Predictable litter due date
• Plug is not a guarantee of pregnancy
• Requires handling of mice

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DOCUMENTATION

• DOB
• Lineage
• Identification
• Strain
• Sex
• Dates bred
• Weaning information
• Initials