Mouse Breeding colony management

PURPOSE:

The purpose of this policy is to address the health and well-being of mice by ensuring safe breeding schemes and population densities. Overcrowding can be a significant animal welfare issue and is in direct violation of University policies as well as The Guide for the Care and Use of Laboratory Animals. The UW-L IACUC has established the following guidelines for mouse breeding and cage density expectations and requires that all Animal Use Protocols follow one of the common breeding schemes below when breeding laboratory mice (Mus musculus).

REFERENCE: 

Guide for the Care and Use of Laboratory Animals, 8th edition, pages 56-57, 75-77, 107.

GENERAL INFORMATION:

• Optimal reproductive age span: 2 – 10 months; some males can be productive longer 
• Estrus cycle: 4-5 days 
• Post-partum Estrus: estrus that occurs within 24 hours of parturition; thus if a male is left in the cage, the female is likely to become pregnant again while lactating and nursing the new litter.
• Gestation period: 19-21 days
• Weaning age: Generally 21 days old, must be able to eat solid food and reach water source. 
• Mouse Pup: 0-22 days of age, prior to weaning. 
• Adult Mouse: Six weeks of age and older. 
• Spot Change – removal of soiled bedding. New bedding may be added if needed. 

POLICY:

• PI’s are responsible for designating a colony manager, someone who has received specific training on managing mouse breeding colonies, and who will be the primary contact person for the lab. The colony manager is responsible for pregnancy and birth checks, cage card documentation and for separating and weaning according to the guidelines below. Any recurring problems with mouse breeding colony management will be brought to the attention of the IACUC.
• One of the following breeding schemes may be used. Only one male per cage, more than one male would be an exception to this policy and would require IACUC approval.

1. Monogamous non-continuous: Male is removed BEFORE the litter is born

One male and one female are housed together for mating. When the female is noticeably pregnant the male is removed from the cage. This is a preferred method to prevent overcrowding and allows for identification of the dam and sire of the litter. 


2. Monogamous non-continuous: Male is removed AFTER the litter is born.

One male and one female are housed together for mating. To provide more space for the pups, the male is removed at first cage change after parturition. This model takes advantage of postpartum estrus and allows the female to become pregnant and nurse at the same time. It is a preferred method to prevent overcrowding and allows for identification of the dam and sire of the litter. Litters are born approximately 21 days apart. The 3-week old litter must be weaned prior to the birth of the new litter.

3. Monogamous continuous

Male and female left in cage with pups. This model takes advantage of postpartum estrus and allows the female to become pregnant and nurse at the same time and for identification of the dam and sire of the litter. Litters are born approximately 21 days apart. The 3-week old litter must be weaned prior to the birth of the new litter to prevent overcrowding. 

4. Polygamous mating

This method houses two (trio) or three (harem) females in a cage with one male. During routine health/breeding checks, each noticeably pregnant female is removed and placed in her own cage. The male may be kept with one of the females to take advantage of postpartum estrus but must be removed at the first cage change after parturition. Only one nursing female and litter is allowed per cage.

• All mouse cages must have nesting material.

• After pups are born, the cage should be left undisturbed for at least three (3) days except to replenish food and water as needed. If the cage gets very dirty or wet, it may be spot changed.

• Weaning age for pups is routinely 21 days of age. Exceptions must be approved by the IACUC or the veterinary staff (based on medical necessity). Allowing a 3 week old litter to stay in the cage with a lactating female that also has a newborn litter is NOT permitted. If a litter contains only one pup of a given sex, provisions must be made to house this pup with others of the same sex. At the time of weaning, a small amount of chow must be provided on the cage floor for the next seven days. In some cases, it is beneficial to provide weanlings with gel packs to ensure hydration. 

• Male and female pups are separated at the time of weaning, with each sex being placed in a separate cage. It is recommended that sexing of the pups be verified one week later. When mice are weaned, they are weaned to adult specifications to avoid needing to separate them and re-house them in 2–3 weeks.

Maximum Cage Densities
The following is the maximum cage density for a standard mouse cage:
• Five compatible adults (<25g).
• One adult breeding pair with or without nursing litter (monogamous pair).
• Only one lactating female with nursing litter are allowed per cage.
• Certain strains may have small litters or do not lactate well so it may be beneficial to house two lactating females together in one cage so they can raise their litters cooperatively. This must be pre-approved by IACUC.

Required Documentation and Cage Cards
An animal use record must be maintained. This record must include the number and disposition of all animals produced. 
General cage cards must include the following information:
• Principal Investigator (last name)
• IACUC protocol #
• Source
• Strain or stock and specific GEM or mutant nomenclature
• Date of birth (DOB)
• Number of animals and sex

Breeding cards must also include:

• Date paired 
• Date separated 
• DOB 
• Projected weaning date of new litter
• # Born 
• Date weaned

  
Adoption Date: 1/18/16 
Amended: 
Reference minutes: 1/18/16