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Biomethodology of the Rabbit
•Routine Technical ProceduresA. Nomenclature and Breeds
•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.
•Non-albino breeds, such as the black and white Dutch belted rabbit, tend to be preferred where pigmentation is required (i.e. ophthalmological research).
B. Unique Biological Characteristics
•The rabbit“s skeleton comprises only 7% of their total body weight (versus the cat skeleton which is 13%). The light skeleton leads to a greater opportunity for spontaneous vertebral fractures (broken backs) due to kicking of the rabbits strong rear legs if they are restrained improperly.
•The "dewlap" is a large fold of skin under the chin and is most prominent in female rabbits.
•Rabbits have hyposegmented neutrophils called Pelger-Huet cells.
•The long slender ears and visibility of the peripheral vasculature in albino rabbits is advantageous for blood collection.
•Rabbits like rodents have two large upper incisors and two large lower incisors. Unlike rodents, however, an additional pair of incisors(peg teeth) are located caudal to the large upper incisors. 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.
•Rabbit teeth continue to grow throughout life. Malocclusion occasionally occurs in rabbits preventing normal tooth wear. This results in severe overgrow of the teeth by inhibiting normal mastication.
•The neutrophil of the rabbit resembles an eosinophil, due to the numerous intracytoplasmic eosinophilic granules, and are called pseudophils.
•Numerous genetic mutations have been noted in the rabbit2 and several inbred rabbit strains have been produced.
•Polyclonal antibody production
•Orthopedics
•Ophthamology
•Infectious disease
•Atherosclerosis
•Pyrogen testing
•Draize testing
A. Blood Collection sites
•large volume — intracardiac (terminal procedure only)
•moderate volume—marginal ear vein, lateral thoracic vein, central ear artery
•small volume—lateral metatarsal vein, toe nail clip
B. Polyclonal Antibody Production
•Conventional rabbits are readily available from several commercial sources. SPF rabbits and genetically unique animals are not as readily available and may take longer to acquire.
•For routine orders, commercially bred rabbits from Charles River animals must be ordered by Tuesday at 9:00 a.m. for delivery by Thursday of that week.
•A source list of mutant and inbred rabbits is available from the Institute of Laboratory Animal Resources.3
•Conventional rabbits will be entered into a conditioning program on arrival and will be held for 7 days before experimental use to allow for prophylactic treatment for coccidia and to allow for recovery from the stress of shipping.
•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 severe scratches to the handler from the toe nails on the rabbits powerful rear legs.
•Rabbits are herbivores and have the unique characteristic of re-ingesting soft fecal pellets ("night feces") directly from the anus. This process of "pseudorumination" allows the acquisition of B vitamins that have been produced by microorganisms in the cecum.
•Defensive behavior in rabbits includes thumping on cage floor with rear feet. Some aggressive rabbits will also charge the front of the cage.
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<TBODY> Adult body weight: male |
2-5 kg1 |
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Adult body weight: female |
2-6 kg1 |
|
Life span |
5-6 up to 15 years1 |
|
Food consumption |
5 g/100 g/ day1 |
|
Water consumption |
5-10 ml/100 g/day6 |
|
Rectal Temperature |
38.5-39.5C4 |
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Heart rate |
205-235/minute6 |
|
Respiratory rate |
30-60 per minute1 </TBODY> |
•Rabbits can be grouped by their microbial colonization and both are available for purchase.
•Specific Pathogen Free (SPF) rabbits are free from several common pathogenic organisms such as Pasteurella, Encephalitzoonois, and Coccidiosis and 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.
•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.
•Rabbits may also be gang housed in a large room, directly on bedding. Bedding material should be placed over cardboard liners to prevent damage to the underlying floor from urine. Care should be taken in selecting bedding materials—the ink on shredded newspaper can discolor the rabbits fur, and straw, which is dusty, can cause upper respiratory problems and conjunctivitis. A shredded, white paper material, such as Enviro-dri™, has proved to be efficacious.
•Water is typically provided through either a "lixit valve" that provides water at all times or by a 1 liter bottle. The “lixit valve” on cages must be checked frequently to make sure it has not become plugged. The water bottle is attached either to the front of the cage or pen. Food is provided by an elevated “J” hopper also attached to the front of the cage or pen. Use of the “J” hopper prevents the rabbit from defecating in their food, which can occur with the use of food crocks (bowls). Water lixit valves and feed hoppers are checked daily by caretakers to insure the provision of food and water.
•The drop pans are changed by the husbandry staff twice per week, and the rabbit is placed into a new sanitized cage every two weeks. Bedding in gang-housed areas is changed once weekly.
•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. Newly received rabbits are placed on an incremental feeding regimen over a 4 day period to acclimate them to the new feed and prevent diarrhea.
•Rabbits are provided with a 12 hours of light each day.
Housing parameters:
•Room temperature - 64-70 F
•Humidity - 40-70%
•Ventilation - 10-15 air changes per hour
•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 via ear tattooing is commonly performed by the vendor before the rabbits are shipped to the facility (add picture).
•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.
•Grasping the loose skin over the neck and shoulder, with the head directed away from the holder, is the best method of initial restraint. 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. If the rabbit begins to struggle, 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.
•Rabbits should never be restrained or lifted by the ears.
•If properly used, commercially available rabbit restrainers help to avoid injuries.
•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.
•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 hind legs.
•Rabbits should never be left unattended in restraint devices. Training in the use of these devices can be arranged through the DLAR veterinary staff.
•A male rabbit is called a buck. A female rabbit is called a doe.
•Rabbits can be sexed by causing eversion of the penis or vulva when slight pressure is applied to the external genitalia.7
•Rabbits are induced ovulators and can have pseudopregnancies.
•Gestation in the rabbit is 29-35 days.
•Parturition in rabbits is known as kindling.
•Rabbit pups are born fully furred with their eyes closed.
•Pups are weaned at 28 days of age.
•Pups are normally nursed only once a day by the doe.
•Rabbits that are moved indoors can be transported in a cat carrier. A paper liner should be placed in on the bottom of the carrier to catch urine and feces. Cat carriers can be obtained from the DLAR veterinary staff.
•Transport always results in some stress to the animal, however, rabbits should recover from indoor transport within their own cage in an hour. No recovery time may be needed if the animals are moved with care and have become accustomed to routine transport.
•Only DLAR husbandry or veterinary staff members can transport rabbits to other buildings or to other animal facilities. Investigators can request animal transportation by contacting the business office at 444-2194. Transport requests should be made 48 hours in advance to allow scheduling of staff.
•Group housing is the main form of housing for rabbits in DLAR. This allows for social interaction.
•Frequent handling by personnel is important and increases the ease of working with these animals.
•Food/chewing items can be made available as rabbit enrichment including wood chew sticks and vegetable treats.
•Rabbits enjoy enclosed areas to use as "burrows" such as large bore plastic tubes.
•If animals cannot have environmental enrichment opportunities because of the nature of the research, please contact the DLAR Director or the Clinical Veterinarian.
•Personnel can receive severe scratches by the rabbit’s hind feet. These scratches can easily become infected. As always, it is important to clean the wound promptly and seek medical attention, when appropriate.
•A tetanus vaccination is required for all personnel working with animals.
•Allergy to rabbit dander is not uncommon. Sensitive personnel should wear face masks and/or respirators (properly fitted), gloves and a lab coat. Personnel should alert Occupational Medicine during their annual health risk assessment and if allergy is a problem, obtain advice and treatment from the Occupational Medicine physician.
A. Monitoring
•Investigators should monitor their animals routinely for common signs of illness, such as:
•loss of appetite
•weight loss
•diarrhea
•nasal or ocular discharge
•lethargy
•unkempt appearance
•The frequency of monitoring of the animal by the investigator is stated in their approved IACUC protocol. Early endpoints are also defined in the protocol and the investigator is responsible for euthanize their animals when these early endpoints are reached.
B. Reporting Sick Animals
•Research personnel are responsible for monitoring their experimental animals as approved in their IACUC protocols.
•If an animal is identified with either experimental or non-experimentally related illness, the investigator should notify the DLAR veterinary staff at 444-2194 between the hours of 8:00 a.m. and 5:00 p.m., Monday through Friday.
•If the investigator needs to contact a veterinarian on the weekend, the veterinary “on-call” list is posted in the main entry area of all DLAR facilities and provides the name, home phone number and pager number of the veterinarian on duty.
•When contacting the veterinarian, please provide the following information:
•Investigators name/ your name
•Species of animals and animal ID number
•Location of the animal (building, room #, rack or cage #)
•Signs of illness
•Description of the experimental manipulations performed, if any.
•Phone number where you can be reached.
•In emergency situations, if an animal needs immediate veterinary care, call the main DLAR office at 444-2194. The DLAR office will send an emergency (911) page or radio the veterinarian. If the emergency occurs after hours, call the veterinarian directly as described above.
1) Harkness JE, Wagner JE. The Biology and Medicine of Rabbits and Rodents, 3rd Edition, Lea and Febiger, Philadelphia, PA,1989.
2) Manning PJ, Ringer DH and Newcomer CE.The Biology of the Laboratory Rabbit, Academic Press, New York, NY, 1994.
3) Institute of Laboratory Animal Resources, National Academy of Sciences, National Research Council, 2101 Constitution Avenue, Washington, DC.
4) Ruckebusch,Y, Phaneuf LP, and Dunlop R, Physiology of Small and Large Animals. Editor Dekker, Philadelphia, PA, 1991.
5) The UFAW Handbook on the Care & Management of Laboratory Animals, 6th Edition; Editor Poole TB, Longman Scientific & Technical, England, 1986.
6) Fox RR, Crary DD. A simple technique for the sexing of newborn rabbits. Lab. Anim. Sci . 22:556-8, 1972.
8) Assistant Laboratory Animal Technician Manual, American Association for Laboratory Animal Science, Bookcrafters, Chelsea, MI, pg. 125-128, 1999.
9) Suckow MA, Douglas FA. The Laboratory Rabbit, CRC Press, Boca Raton, NY, 1997.