Ammonia levels were high by day
seven in cages housing four mice but
this appeared unrelated to cage-cleaning
as it was observed in both control and
Reducing labor, water, and energy are
some of the benefits that may result from
decreasing the frequency of washing
cages. This study provided preliminary
data relevant to establishing a validated
frequency for sanitization of rodent caging.
Gabriela Fuentes-Creollo, Ph.D., is the
Animal Facility Manager at Lawrence
Berkeley National Lab, she received her
doctorate in veterinary medicine from the
Universidad Autonoma Metropolitana
in Mexico City and has over 15 years of
extensive experience in the veterinary
Nina Hahn, DVM, Ph.D. (UC Davis
’84) is Attending Veterinarian overseeing
animal care and directing personnel for
many institutions in the San Francisco
Bay Area including Lawrence Berkeley
There are many reports relating to fre- quency of bedding change, however, there is no published information
supporting the biological rationale for
weekly cleaning of the solid cage itself.
Decreasing the frequency of cage-wash-ing could have considerable impact on
labor, energy, and water-use efficiency
in a rodent facility. In this study, organic
contamination of cages that had weekly
bedding changes but no additional sanitation for six weeks was compared to contamination of cages that were completely
sanitized every seven days.
There were no evident differences in
body weights, ammonia levels, ATP, or col-ony-forming units as measured by RODAC,
between control cages that were replaced
with freshly sanitized cages every week,
and experimental cages that had only
soiled bedding changed.
MATERIALS AND METHODS
Female ICR mice (n= 17, 30 weeks old)
were obtained from a commercial vendor
and housed in one large room held in one
of five self-contained areas.
The static microisolater cages contained
autoclaved corncobs and paper nesting
material. The protocol was approved by
the Lawrence Berkeley National Laboratory
(LBNL) Institutional Animal Care and
Use Committee, and was performed in an
Two control cages containing 4 and 2 mice
were completely cage-changed (including
cage and bedding/nesting) according to
standard practice at LBNL, every 7 days.
Four experimental cages housing 4 (n=1)
3 (n=1) and 2 (n= 2) mice were not
changed or washed, but soiled bedding/
nesting was dumped and
fresh autoclaved material
added at each time-point: 7,
14, 21, 28, and 36 days. The
ammonia concentration was
measured in each group prior
to dumping the bedding at
each time point. The ammonia was measured using a gas
detection pump. RODAC and
ATP samples were obtained
from inside the cages after the
bedding was dumped in both
groups (Figures 1 and 2).
Body weights were taken at
every time-point for all cages.
RODAC and ATP were difficult to interpret, and there were not enough cages
for meaningful statistical interpretation.
However, there was no indication based
on ammonia levels, RODAC, or ATP that
cage-sanitation resulted in cleaner environmental conditions for the mice.
Is Weekly Sanitation of the Entire
Mouse Cage Really Necessary?
Reducing Labor, Energy, and Water Use
Figure 1: Sampling ATP at center of cage
Figure 2: Bedding before dumping