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UNIVERSITY OF SOUTHERN MAINE
Office of Research Integrity & Outreach
Procedure #:
Date Adopted:
Last Updated:
Prepared By:
Reviewed By:
Procedure Title:
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6/9/2005
2/14/2012
Sarah Gilliam, Animal Facilities Manager
USM IACUC Committee
Rodent Breeding Policy
1.0 Purpose: To ensure that proper care and handling is utilized in order to maximize
breeding success.
2.0 Responsibility: It is the responsibility of the investigator, technician, or student
performing the task to follow the procedures established in this document.
3.0 Applicable Documents:
3.1 SOP 02-001: Animal Space Provision
3.2 SOP 02-002: Animal Identification Policy
3.3 SOP 03-003: Mouse Procedures
3.4 SOP 03-004: Rat Procedures
3.5 SOP 03-009: Observation of Vaginal Plugs
3.6 SOP 04-003: Rodent Husbandry
3.7 Appendix A: Breeder Cage Card Sample
4.0 Materials & Equipment:
4.1 Appropriate cage for species and size
4.1.1 Refer to SOP 02-001: Animal Space Provision
4.2 Nesting material
4.2.1 NestletsTM (Ordered through Ancare)
4.2.2 Other autoclavable nesting material approved by the Animal
Facilities Manager and the consulting veterinarian
4.3 Breeder Cage Cards
4.3.1 Refer to Appendix A: Breeder Cage Card Sample
5.0 Procedure:
5.1 Choosing the breeding pair:
5.1.1 Things to consider:
5.1.1.1 Type of research project
5.1.1.2 Type of breeder pair
5.1.1.2.1 Monogamous: one male & one female
5.1.1.2.2 Polygamous: one male & several females
5.1.1.2.3 Continuous or Non-Continuous breeding
5.1.1.3 Age of animals to breed
5.1.1.3.1 Mice: optimal breeding age is 6-8 weeks up to
6-8 months
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5.1.1.3.2
Rats: Female optimal age is 8-9 weeks up to
12-15 months, male optimal age is 10-12 weeks
up to 12-15 months
5.1.1.3 Strain of the animal-several strains are known to be poor
breeders.
5.1.1.4 Appearance & overall health of the animal
5.1.1.5 Prior reproductive performance
5.2 Setting up the breeding pair:
5.2.1 New breeder pairs should be placed into a clean cage &
nesting material(s) should be provided (unless the
investigator specifically requests that no nesting material be
placed into the cage).
5.2.2 A breeder pair cage card should be filled out and used on
each breeder cage. See Appendix A for an example.
5.2.3 The male should be placed into the cage first. The female(s)
are introduced to the cage second.
5.2.4 After the animals are placed into the cage, some aggressive
behavior may be observed, as well as vocalizations. The
animals should settle down after a few hours.
5.2.4.1 If the animals are overly aggressive (i.e.-fighting and
causing obvious injury to one or the other or both) then the
animals should be separated and another set chosen.
5.3 Detection of Pregnancy:
5.3.1 After mating, a vaginal plug forms and can be observed for
up to 24 hours. Refer to SOP 03-009: Observation of
Vaginal Plugs for the appropriate detection.
5.3.1.1 Presence of a vaginal plug does not guarantee pregnancy.
5.3.2 A pregnancy can also be detected beginning approximately at
day 10-12 post-conception. This is done by simple palpation.
5.3.2.1 First restrain the female in accordance with SOP 03-003:
Mouse Procedures and SOP 03-004: Rat Procedures.
5.3.2.2 Once properly restrained, use the free hand to press down
on the abdomen, towards the spine, and use the thumb and
forefinger to run down the sides of the animal. Initially, a
pregnant female will feel like she has a string of pearls
along each side of her body.
5.4 Gestation:
5.4.1
5.4.2
The gestation period for both rats and mice is 21 days, with
some variance due to litter size and strain of the animal.
If the breeders are polygamous, then the confirmed pregnant
females should be separated out into individual cages for
parturition.
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5.4.3
If the breeders are monogamous, then the male should be
separated out once the female is confirmed pregnant.
5.4.3.1 If the investigator or protocol calls for the breeders to
remain together as a ‘continuous’ breeder pair, then the
male will remain inside of the cage so the female will mate
during her post-partum estrus.
5.5 Postnatal Period:
5.5.1 Do not touch or manipulate the mother or pups until the pups
are at least 3 days of age unless there is a problem or unless
an IACUC approved protocol requires it.
5.5.1.1 Some problems that can occur & require the premature
handling of the animals: include cannibalism, inability to
nurse, rejection of the litter, death of the mother, or water
bottle leak.
5.5.2 Fresh gloves should always be put on before handling new
mothers and newborn pups. This will prevent the scent of
foreign litter or chemical from transferring to the newborn
litter. This can aide in retention of the litter.
5.5.3 Healthy newborns will nurse immediately and a ‘milk spot’ is
visible through their bodies.
5.5.4 Normal development: Newborn-pink & hairless with eyes
and ears close; Day 4-7- ears begin to open; Day 10-full
covering of hair; Day 10-14-eyes are open; Day 14-begin to
eat solid food.
5.6 Foster Parenting:
5.6.1 Reasons for a Foster Mother:
5.6.1.1 Newborn pups not receiving sufficient nutrition from the
original mother.
5.6.1.2 Experimental design of the protocol.
5.6.1.3 Too many pups for the original mother to care for properly.
5.6.1.4 Death of the original female.
5.6.1.5 Rejection of litter from the original female.
5.6.2 Procedure:
5.6.2.1 For the foster mother, choose an experienced female with
her own newborn litter (date of birth should be within 2
days of the litter to be cross-fostered).
5.6.2.2 Using fresh gloves, remove the entire litter from the foster
mother’s cage and place them into a separate, clean cage
temporarily.
5.6.2.3 The new litter should be a maximum of 9 pups, to prevent
overwhelming the foster mother. Some of the foster
mother’s pups may need to be permanently removed.
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5.6.2.4 If there is a need to determine between the foster mother’s
original pups and the pups that are being fostered, then the
pups should be identified or marked accordingly.
5.6.2.5 Once the pups have been identified, add the pups from the
original female to the foster mother’s cage. Then replace
the foster mother’s original litter.
5.7 Weaning:
5.7.1 Rats and mice are normally weaned at 21 days of age.
5.7.1.1 In some cases, such as an undersized litter, it may be
necessary to leave the pups with the mother until they are
able to survive on their own.
5.7.2 The pups should be divided by sex, with males and females
going into separate, clean cages. The animals should be
housed in accordance to SOP 04-003: Rodent Husbandry and
SOP 02-001: Animal Space Provision.
5.7.3 Identify each cage & the animals within on the cage card in
accordance with SOP 02-002: Animal Identification Policy.
5.7.4 The number of weaned animals and cages should then be
added to the census sheet.
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Appendix A:
Breeder Cage Card Sample
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