Biomedical Engineering Reference
In-Depth Information
Cages should accommodate a method to affix identifi-
cation of the animal(s) housed within the cage. Cage cards
are frequently used for this, but if used, the cage cardholder
should be designed and attached to the cage in a manner
and location that prevents the inhabitants from removing or
soiling the card. Stamped metal tags attached with locks or
other fasteners are an alternative. Identifiers need to be
moved to the clean cage during cage wash, but should also
be sanitized. Technologies utilizing barcode scanning or
radio frequency identification (RFID) are being developed
and utilized for animal identification (
Lucid and Lepid,
2010
).
dependent on multiple facility design issues that should be
considered before cage racks are purchased. Casters should
be constructed with materials that do not mark or dent
floors, but can be processed through cage washers with
water temperatures exceeding 180
F. Racks used in appli-
cations that will require sterilization should be equipped
with casters that will withstand the pressure and tempera-
ture conditions produced in the autoclave. Casters should
be sized appropriately to allow easy movement over floor
gaps such as thresholds or elevators. Larger-diameter
casters increase overall rack height, so doorway dimensions
should be checked before selection, if several caster sizes
are available.
Cage Support System
Cages may be wall mounted with brackets or be supported
by moveable cage racks. Wall-mounted systems require the
cages to be washed in place or removed from the bracket
system. Cages may be removed by lifting them from the
supporting brackets, either manually or with the aid of
a mechanical hoist. Although wall-mounted cage systems
may be less costly than the cage rack system, the support
brackets impede sanitation and provide harborage for
vermin. As cages become larger and heavier, the weight
and torque placed on the wall and the supports may cause
damage to these structures. Heavier cages are also more
prone to cause human injury.
Movable rack-mounted cage support systems may hold
from one to six cages depending upon the cage size. Racks
are usually mounted on casters to allow mobility and may
be sanitized in a rack washer. Cage racks must be sized to
move easily through animal rooms, corridors, and service
room doors of the facility. One-over-one racks are being
utilized because of flexibility and ease of movement
compared to larger racks. However, they generally are more
expensive, per cage. Cage racks used to house medium to
large nonhuman primates should be able to be secured to
a wall or other permanent building structure so that animals
cannot move or tip over the racks.
A very important part of mobile caging is casters
(wheels). Casters come in a variety of designs, and some
are better designed for turning and locking than others.
Advancements in caster technology should be considered
when specifying features of caging to be purchased. For
example, at the time the original chapter was published
(
Kelley and Hall, 1995
), it was a common requirement to
have grease zerks on the wheel axel and the swivel race
because of the rusting of bearing materials. Today, there is
hardly a new caster purchased without stainless steel ball
bearings in the swivel race, and sometimes in the wheel
axel. Self-lubricating Delrin sleeve-type bearings are
generally used in the wheel axel. These features eliminate
the need for greasing the bearings on the casters. The
necessity to have four casters turn or only one set turn is
Waste Collection
Most nonhuman primate cages with welded wire floors
have waste pans located under the cage floor. Some facil-
ities instead allow the waste to fall onto the floor or into
a trench where it is flushed into a drain. Regardless of the
type of waste collection system used, the surface should be
located far enough below the cage floor so the inhabitant
cannot reach the waste pans. This may be difficult to
accomplish because of the height of the entry door or the
height of the room ceiling. If cages are stacked in tiers of
two units, the distance available between the upper and
lower cage may be limited. This may increase the likeli-
hood of injuries caused by fights between animals when the
pan is removed for cleaning. A short distance between
cages may also further block light into the lower cage.
Removable Pans
Waste may collect in individual removable pans located
underneath the cages. Pans are then removed for dumping
waste and sanitization. Waste pans should not be cleaned in
animal rooms. Absorbent, noncontact bedding may be used
in the pans to absorb moisture. Sanitization is best
accomplished in a mechanical washer. However, washing
and disinfection of equipment by hand with hot water and
detergents or disinfectants can be effective but require
attention to detail (
National Research Council (Institute for
Laboratory Animal Research), 2011
).
Removable pans reduce the potential for transfer of
disease between cages and minimize creation of the aero-
sols during sanitization procedures. They also allow more
types of environmental enrichment than flush pans, where
clogging drains is an issue. Additionally, removable pans
may be useful for procedures requiring monitoring of
output or collection of urine or feces for analysis.
Disadvantages of removable pans are: they may be
difficult to transport, they are more labor intensive, and they
may require extra equipment for frequent changing. Also,
some primates learn to push pans onto the floor if not securely
clamped. During pan cleaning, primates may be able to
