Space Requirements for Rodent Housing. (breeding)
The following is a policy for “Minimum Space
Recommendations for Laboratory Animals". In order to
remain in compliance with the Guide, rodent density
must be maintained within prescribed limits. Case IACUC
policy regarding overcrowding of rodents is described
below.
All investigators or other animal users are required
to adhere strictly to the minimum space recommendations
as promulgated for all common species in the Guide,
unless a specific request for an exception to these
rules has been included in the experimental (or breeding)
protocol and approved by the IACUC.
Any request for a waiver of the established rules
must be accompanied by a sound scientific justification
for the practice acceptable to the Committee. Investigator
convenience or economies are not acceptable reasons
for granting a waiver of the regulations.
Litters of substantially different ages are not
permitted to share a cage unless the justification
for, and conditions of, such a practice are accepted
by the Committee on a case by case basis.
Requests for waivers must be accompanied by a specified
maximum necessary cage density for approval (or modification)
by the Committee and which, if exceeded, will authorize
the cage to be designated as overcrowded.
All cases of unacceptable rodent cage densities
are periodically reported by the Training & Compliance
Coordinator to the IACUC at its regular monthly meetings.
Investigators who are working with an already-approved
protocol, and whose experimental design necessitates
their employing cage densities in excess of the PHS
standards, must submit an addendum specifying the
maximum density they feel is necessary and providing
the required scientific justification for their position.
The placing of an "overcrowding" Morbidity and
Mortality Report on the affected cage will, in itself,
constitute sufficient notice to the investigator.
However the ARC will attempt to contact him/her by
telephone as soon as the card is placed. A single
(attempted) call to the investigator's laboratory
will be deemed sufficient additional notification.
If after expiration of the 48 hour grace period
(which includes holidays and weekends), the cage
overcrowding has not been relieved, the ARC staff
will proceed with the separation and will identify
the several cages into which the animals have been
placed in such a way as to permit the investigator
to reconstruct the composition of the original cage.
This technical time required to perform this service
will be charged to the investigator.
In cases where the observed overcrowding exceeds
200% of the PHS allowable minimum space requirements,
the ARC staff may proceed with the separation without
notification of the investigator or the provision
of a grace period. This service will is fully chargeable
to the investigator. An attempt to contact the investigator
will be made but animals in these cages will ALWAYS
be changed on the same day.
Where more than one pregnant rodent is housed in
a cage, the ARC may place an "ANTICIPATED OVERCROWDING" card
on the cage (and attempt to contact the investigator).
The ARC staff may then separate the animals after
48 hours have passed or at the birth of the litter(s)
whichever is later without further notice to the
investigator.
All rodent cage cards should record the mating
date(s) of the females and/or the birth dates of
the litters in addition to Investigator name, protocol
number and telephone number.
Non Breeding Mice per Cage Consideration.
Investigators should be aware that housing 5 mice
per cage can be noncompliant with regulations. Mice
heavier than 25 grams must have at least 15 square
inches of floor space per mouse. Standard mouse shoeboxes
used at the ARC provide 68 square inches of floor space.
According to current PHS and AAALAC regulations this
can accommodate 5 mice <25 grams, or 4 mice >25
grams. Supermouse cages in use in some ventilated microisolator
racks provide 75 square inches of floor space and can
therefore accommodate 5 mice of any size. The ARC will
be introducing standard cages which have 75 square
inches of floor space, however this will not be completed
for some time.
Breeding of Mice.
Recommendations of number of mice per cage (breeding
cages):
Pair breeding: 1 male and 1 female
Entire litter may remain with parents until 3-4
weeks of age or after birth of next litter whichever
is sooner.
Trio breeding: 1 male and 2 female
Providing that litters are born within 1 week of
each other, cages may be maintained with 3 adults
and 2 litters for one week after birth of the pups, then one mother must be removed with one half of the pups. As mice will co-nurse each others litters, it makes no difference which pups go with which moms.
Harem breeding: 1 male and 3 or 4 females
Remove 1 or 2 females when pregnancy determined
by physical examination (plug) or enlargement. Then
remove females to bring to situation as described
for trio breeding.
For some mutant strains with weak or neurologically
compromised immune systems, mice pup survival is improved
by keeping affected pups with their dam in excess of
4 weeks. If this practice is necessary it should be
described in your IACUC protocol.
Investigators should be aware that housing 5 mice
per cage can be noncompliant with regulations. Mice
heavier than 25 grams must have at least 15 square
inches of floor space per mouse. Standard mouse shoeboxes
used at the ARC provide 68 square inches of floor space.
According to current PHS and AAALAC regulations this
can accommodate 5 mice <25 grams, or 4 mice >25
grams. Supermouse cages in use in some ventilated microisolator
racks provide 75 square inches of floor space and can
therefore accommodate 5 mice of any size. The ARC will
be introducing standard cages which have 75 square
inches of floor space; however this will not be completed
for some time.
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