The University of Iowa

Rodent Breeding Colony Management

Rodent Breeding Colony Management

***All breeding animals in the same cage must be under the same approved animal protocol number (AP) for which the breeding is intended for. This may require a "transfer" transaction slip being completed and processed before breeders are set up.*** 

  • Upon request, OAR will train research staff how to manage their breeding colonies:
    • Setting up breeding pairs
    • Weaning
    • ID system
    • Tail snips
  • Male rodents should never be combined for housing
    • Exception:  littermates that were always housed together and not used for breeding may remain housed together
    • For more details refer to the Policy on Housing of Social Species

Cage cards required in a breeder cage

  • A completed standard white cage card is needed for each animal
    • White card

  • A complete green breeder card must be placed in any cage where a litter may be born/expected
    • Examples of conditions where a litter may be born/expected include
      • Time pregnant dams
      • Mis-sexed cage
      • Sentinel dams in quarantine rooms
      • Recipient dams via embryo transfer
    • The green breeder card follows the female if she is removed from the cage
    • Breeder card

Procedure for paired breeding

  • House one male mouse with one female house (a pair) in a clean cage
  • Assure access to food and water
  • Cage cards
    • Male
      • Must have a completed standard white cage card
    • Female
      • Must have a completed standard white cage card
      • Must have a completed green breeder card

Procedure for harem breeding

  • Set-up one male mouse with up to three female mice in a cage
  • Cage cards
    • Each female
      • Must have a completed standard white cage card
      • Must have a completed green breeder card
    • Male
      • Must have a completed standard white cage card
      • Male may be rotated among the females that were separated (set up in clean cage) for future breeding
  • Required separation of animals
    • No more than two adults and one litter may be present in a mouse breeder cage at once
    • Each female housed in a harem must be separated into her own cage (by laboratory staff) once it shows signs of pregnancy
      • Separation of the pregnant dam must occur to maintain cage space requirements1 prior to delivery of the litter
    • Cage cards must move with the animals
      • Female: the green breeder card and the white cage card must move with her when separated
      • Male: the white cage card must move with the male when he is placed in a different cage

Procedures for weaning

  • What is weaning?
    • Weaning is the act of separating the young mice/rats into their own cage at a time where they are ready and able to live on their own
    • Rodent litters must be weaned at day 21 +/- 3 days (18-24 days) post birth
  • Procure new cages (filter top, food hopper/wire bars and cage bottoms)
  • Add feed to the cage and verify that the water valve is working properly
  • Assure you have generated additional white cage cards to identify the animals that will be weaned
    • Correctly enter the investigator, hawkID, animal protocol, account, date of birth, sex, and umber of mice per cage, contact staff and additional identifying information as requested/necessary
    • An individual white card (one card per rodent), is not necessary/mandatory; these individual cards may be generated at the discretion of the lab
  • Separate rodents by sex
  • No more than 5 non-breeding mice may be housed per cage
    • This may vary based on mouse size/strain and research use
      • See an OAR facility supervisor for further information
    • Each cage of weanlings must have a completed standard white cage card

Collection of genetic material for Genotyping

OAR Breeder Informational Cards


  • Please refer to the following link for details about conditions associated with breeding practices that will generate charges to an investigator

OAR Rodent Breeding Colony Management - Fee for Service

  • OAR can offer management of breeding colonies (must be approved by OAR) for a fee.  Fee structures may be found here

OAR’s cage and ear punch identification system

  • OAR has adopted a simple rodent identification system. 
  • This system is used when OAR husbandry and/or veterinary staff assist in identifying rodents (fee for service)
  • Each cage of animals is given a number
  • Each cage of animals will start with ear punch #1
  • No animal is assigned an ID # higher than 5 as this is the maximum number of weaned animals that may be housed in a cage



    1. Guide for the Care and Use of Laboratory Animals: Eighth Edition. Washington, DC: The National Academies Press.