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Of the many breeds of the domesticated European rabbit (Oryctolagus
cuniculus), the albino New Zealand White is the most common breed utilized
in biomedical research. The visibility of the peripheral vasculature in
albino rabbits is advantageous to the biomedical use of this rabbit.
Non-albino breeds such as the black and white Dutch belted rabbit tend to
be preferred where pigmentation is required (i.e. ophthalmological
research). Rabbits like rodents have two large upper incisors and two
large lower incisors. Unlike rodents, however, an additional pair of
incisors is located caudal to the large upper incisors (peg teeth). This
additional pair of upper incisors is greatly reduced in size and is why
rabbits are members of the order Lagomorpha rather than the order Rodentia.
Rabbits have several unique anatomical characteristics. As previously
mentioned the long slender ears of the albino New Zealand White breed
facilitate phlebotomy procedures. The long backbone predisposes rabbits to
spinal fractures, if not captured and restrained properly. Rabbit teeth
continue to grow throughout life. Malocclusion occasionally occurs in
rabbits preventing normal tooth wear resulting in severe overgrow of the
teeth inhibiting normal mastication. The neutrophil of the rabbit
resembles an eosinophil due to the numerous intracytoplasmic eosinophilic
granules.
Rabbits can be grouped by their microbial colonization: "Specific
Pathogen Free" (SPF) rabbits are free from several common pathogenic
organisms such as Pasteurella , Encephalitzoonois, and Coccidiosis. SPF
rabbits are bred specifically for research use. "Conventional" rabbits
tend to be colonized with the preceding organisms which can occasionally
be detrimental to their health and longevity. Conventional rabbits are
bred primarily for food and fur. Unlike SPF rabbits, conventional rabbits
are widely available and if appropriate for the project can represent a
substantial savings upon purchase. The investigator must weigh these
considerations when choosing the type of rabbit for purchase. Numerous
genetic mutations have been noted in the rabbit15
and several inbred rabbit strains have been produced.
Conventional rabbits are readily available from several commercial
sources. Vivarium
personnel are familiar with many of the commonly available strains
and will assist in locating animals available for purchase.
To order
animals the investigator must provide the UC Riverside Animal Use
Protocol number.
The rabbits are gentle animals and if care is taken become accustomed
to handling if they are not upset by the experience. Inappropriate
handling can result in toenail scratches to the handler from the toe nails
on the powerful rear legs . Rabbits are herbivores and have the unique
characteristic of reingesting soft fecal pellets directly from the anus.
This process of "pseudorumination" allows the acquisition of B vitamins
that have been produced by microorganisms in the cecum.
| Adult body weight: male |
2-5 kg5
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| Adult body weight: female |
2-6 kg5
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| Life span |
5-6 up to 15 years5
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| Food consumption |
5 g/100 g/ day5
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| Water consumption |
5-10 ml/100 g/day22 |
| Rectal Temperature |
38.5-39.5C20
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| Heart rate |
205-235/minute21
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| Respiratory rate |
30-60 per minute5
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Most rabbits are housed in stainless steel cages with a fenestrated
floor to allow feces to drop through into a pan. Absorbent material is
placed in the pan to collect urine and minimize ammonia release due to the
bacterial breakdown of urea. Caged rabbits are typically housed
individually, however, some cages allow for pair housing. Rabbits less
than 2 kg in weight are provided with 1.5 square feet of floor space.
Rabbits weighing from 2-4 kg are maintained in 3 square foot cages. Water
is typically provided through a lixit that provides water at all times.
The lixit on cages is checked frequently to make sure it has not become
plugged. Water may also be provided via a standard 1 liter water bottle
attached to the wire front of the cage. Food is provided by a J-hopper
attached to the front of the cage. J-hopper's prevent the rabbit from
defecating in their food, which occurs with the use of food crocks
(bowls).
The drop pans are changed by the caretaking staff twice per week, and
the rabbit is placed into a new sanitized cage every two weeks. Water
lixits and feed hoppers are checked daily by caretakers to insure the
provision of food and water.
Pelleted natural ingredient diets are used to feed all rabbits and are
composed primarily of cereal grains which are supplemented with additional
protein, vitamins and mineral. Rabbits receive a high fiber diet which
tends to minimize common gastrointestinal disorders. Due to the nature of
natural ingredient diets, the exact composition can vary substantially
from each vendor. Rabbits are fed a specified amount of diet daily in
order to prevent obesity which tends to occur if rabbits are fed ad
libitum. The water provided to animals is chlorinated tap water.
Rabbits are provided with a 12 hours of light each day with the light
phase starting at 6 am. The temperature in the room is maintained between
60.8 and 69.8 F with a relative humidity ranging from 40-70%.
Cage cards are utilized to identify the strain of rabbit, sex, number,
principal investigator, and research protocol. Cage cards should not be
removed from the cage to avoid misidentification of the animals. Temporary
identification of individual rabbits can be accomplished by pen marks on
the fur, or dyeing the fur. Pen marks or dyes will only last 1-2 days.
Permanent identification methods can be achieved by ear tattooing which
will be performed by vivarium personnel upon request.
When handling rabbits it is advisable to wear latex gloves to prevent
the development of allergies and to provide some safety from rabbit
scratches to the handler. Rabbits seldom bite but can inflict painful
scratch wounds, especially with the hind feet. They should be held in a
way that directs their hind feet away from the handler's body. Grasping
the loose skin over the neck and shoulder with the head directed away from
the holder is the best method of initial restraint (figure
1).
When lifting a rabbit, the lower part of the body must be supported by the other hand to prevent
serious injury to the rabbit's back (figure 2,
figure 3).
Rabbits should never be restrained or lifted by the ears. If the rabbit
begins to struggle violently, it should immediately be placed on a solid
surface and calmed. Struggling frequently leads to fracture of lumbar
vertebrae and injury to the spinal cord that may necessitate euthanasia.
If properly used, commercially available rabbit restrainers help to
avoid injuries (figure 4).
Rabbits may exhibit sudden violent efforts to escape during restraint.
In the process, intravenous needles, gavage tubes, etc. can be dislodged
causing spills or otherwise endangering themselves or personnel.
Therefore, complete restraint should be accomplished before attempting
such procedures and rabbits should never be left unattended in restraint
devices.
Rabbit colonies tend to be very labor intensive and are only
appropriate for rabbits which are not readily available commercially (i.e.
Watanabe rabbits). Investigators requiring the establishment of breeding
colonies should consult with the vivarium manager and the Office of the
Campus Veterinarian to assure proper
management of the colonies. Breeding animals have different requirements
(i.e. nutrition), which if not provided, will have a detrimental effect on
reproductive performance.
Several types of devices are commercially available to restrain
rabbits. Quality devices prevent the animal from turning around or
twisting yet allow easy access to the head and ears (figure
4). Care should be taken
when placing a rabbit in a restraint device since struggling may result in
damage to the spine. Struggling is reduced if the device snugly secures
both the head, back and hindlegs.
Rabbits can be sexed by causing eversion of the penis or vulva when
slight pressure is applied to the external genitalia. (future picture)23
Rabbits should always be transported in a transport cage. Investigators unable to locate an available transport cage should ask the
vivarium supervisor for assistance. Once a transport cage has been used it
should be returned to the cage wash area for sanitation before reuse.
Transport always results in some stress to the animal, however, animals
should recover from indoor transport within an hour. No recovery time may
be needed if the animals are moved with care and have become accustomed to
routine transport. It is recommended that a permeable drape be placed over
the cages to darken the cage and prevent over arousal of the rabbits
during transport. Rabbits cannot be transported out of doors or by
vehicles by other than animal care unit personnel. Investigators can
request transfer to other buildings by contacting the appropriate
husbandry staff.
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