Rabbit Oryctolagus cuniculus

1
Rabbit Oryctolagus cuniculus

• Biology and Uses in Research

2
TAXONOMY

• Class Mammalia
• Order Lagamorpha
• Family Leporidae
• Genus Oryctolagus
• Species cuninulus
• Lagomorphs are distinguished from rodents by
  their incisor teeth.

3
Teeth

• Lagomorphs have six incisor teeth, including the
  small teeth (frequently called peg teeth)
  directly behind the large upper incisors. By
  contrast, rodents have only four incisors.

4
General Information

• Known as the domestic rabbit
• Derived from European wild rabbit
• Used as pets, meat producers or research
• Oryctolagus cuniculus is the only genus of the
  European rabbit
• Hares (lepus) and Cottontails (Sylvilagus) are in
  a different genera
• Fertile cross-genera mating do occur but
  offspring are infertile

5
Breeds and Varieties

• Over 40 different breeds/varieties recognized by
  the American Rabbit Breeder Assn
• Only a few used in meat production and labs
• Many bred just for show quality
• Most have definite molting period

6
Breeds

• Of the six genus in the Subfamily Leporinae, only
  the European rabbit, Oryctolagus cuniculus is
  commonly used in research, testing, or teaching.
  
• Three of the most commonly used breeds are the
  New Zealand White, American Dutch, and
  Californian.

7
New Zealand White

• Most commonly used
• White
• Most popular
• Used for food and laboratory
• Mature weight 10 lbs/4.5 kgs
• Docile

8
American Dutch

• The American Dutch rabbit, is less than half the
  size of the New Zealand White, reaching a mature
  weight of only two kilograms.
• There are several color varieties of the American
  Dutch breed, but the most common is the black and
  white
• Second most popular in research

9
California Rabbit

• Primarily for food
• White fur with dark brown tips on feet, ears,
  nose and tail
• Pigmentation thermolabile
• Mature weight 10 lbs/4.5 kg

10
Chinchilla rabbit

• Mature weight 10 lbs/4.5 kgs
• Steel grey

11
Flemish Giant

• Checkered giant
• Largest breed
• Weight 13 lbs
• Not commonly used too big
• Mature slowly

12
Angora

• Used for fur
• Fur is plucked every 3 months
• 2 2 1/2 inches

13
Netherland Dwarf

• Smallest
• Weight 2-3 lbs

14
Lop Eared

• Medium size
• Weight 5-6 lbs
• Lop ears

15
Hair growth patterns

• The hair growth patterns of the rabbit are
  somewhat unusual. After the rabbit's hair has
  been clipped, it may not grow back uniformly.
• Notice in this rabbit that some patches of hair
  are longer than others. This can make
  interpretation of some skin tests difficult.

16
Skeletal mass

• Only about 7 of the body weight of a rabbit is
  skeletal structure.
• Compare the bone density of a cat (on the top)
  with the rabbit of approximately the same weight
  (on the bottom).
• This is a lateral view radiograph.
• The muscle mass of a rabbit relative to bone
  structure makes it highly susceptible to lumbar
  fracture or dislocation.

17
Dental Formula

• 2x (2/1 I, 0/0 C, 3/3 P, 3/2 M) 28
• Teeth grown and wear continuously

18
Vital signs

• Normal vital signs will vary with the age and
  breed of the rabbit, but for a healthy animal
  they should fall within these ranges
• heart rate 130 - 325
• respiratory rate 32 -60
• rectal temp 101.3 F 104 F

19
Urine

• A healthy rabbit will produce about 50-75 mL of
  urine per kilogram of body weight each day. It
  will normally be dark yellow to brown and will
  appear turbid. This turbidity is due to mineral
  precipitates. Rabbit urine is normally alkaline
  with a pH of over 8.2
• The urine forms scale (a thick mineral coating)
  on cages as it dries.

20
Feces

• Healthy rabbits produce two types of feces.
• The droppings seen in the pan under the cage are
  hard fecal pellets that contain mostly waste
  fiber.
• The other type is a softer feces that is produced
  in the cecum, and is often called cecotrophs or
  night feces. This material is rich in vitamins
  and protein, and the rabbit may consume it
  directly from the anus

21
Ear

• An important feature of rabbits is the prominent
  blood vessels in their ears.
• Rabbit ears are NOT handles and must never be
  used for restraint! 
• The central artery is used for collecting large
  quantities of blood. The marginal ear vein is
  used for giving IV injections or collecting
  smaller quantities of blood

22
Hematology

• The blood volume of a rabbit is approximately 56
  ml/kg body weight.
• Generally, 10 - 15 of the total volume can be
  taken as frequently as every two weeks without
  endangering the rabbit.

23
Hematology

• The normal range for the red blood cell count
  is 4.5 - 7.0 x 103. The total white blood cell
  count and differential fall within the range
  expected of most other species of laboratory
  animals, as shown here
• Total WBC 4.6 - 13 X 103
• Lymphocytes 30 - 50
• Neutrophils 30 - 50
• Monocytes 0 - 3
• Eosinophils 0 - 2
• Basophils 0- 7 (Ref Kozma, et al.).

24
Neutrophil, eosinophil

• The rabbit neutrophil, shown on the left,
  contains granules that stain red with eosin.
• Because of this staining characteristic, rabbit
  neutrophils are sometimes called
  pseudoeosinophils, amphophils, or heterophils.

25
Let's look at a dissection of a rabbit to study
the internal organs that are most commonly
relevant to research uses

• This is a sagittal section of the head showing
  the long oropharynx (red pin), large fleshy
  tongue, and the sagittal niches. It also shows
  the relationship of the esophagus (yellow pin),
  to the trachea (blue pin), epiglottis (below the
  red pin), and nasopharynx (white pin). All of
  these features combine to make passing an
  endotracheal tube difficult

26
Thoracic cavity

• Dissection into the thoracic cavity, shows the
  heart, which is relatively small for the size of
  the animal -- about 1/2 that of a cat of the same
  size. This becomes important when attempting
  to collect blood via cardiac puncture.

27
Lungs

• The lungs differ from each other in size and
  construction. The right lung is normally
  larger, and it has three distinct lobes, whereas
  the left has only two.
• This image shows the bilobed left lung

28
Abdominal cavity

• The abdominal cavity is proportionately large,
  reflecting the high roughage content of the diet.
  The liver lies above the stomach.
• The gall bladder is buried deep in the liver, and
  cannot be seen on this image.
• The cecum is very large, and has about ten times
  the capacity of the stomach...

29
Stomach

• ...which is large, thin-walled, not
  compartmentalized, and relatively aglandular.
  The pH in an adult rabbit stomach is very acid

30
Female reproductive organs

• This image shows the female reproductive organs
  -- the ovaries, uterine horns, and vagina which
  has been cut open longitudinally.
• The uterine horns are separated their entire
  length. Each horn empties into a separate
  cervix and then into the vagina.

31
Placenta

• The placental barrier in the rabbit is
  hemochorial, which means that the membrane
  enclosing the fetus is in direct contact with
  maternal blood. This means it is similar to the
  human barrier, making the rabbit a good model for
  studying transmission of agents through the
  placenta.

32
Reproduction

• The female rabbit is called a doe  she is
  generally larger than the male.  Females have
  four pairs of mammary glands and often has a
  pronounced dewlap (roll of fur under her chin).
• Male rabbits are called bucks.  Bucks have no
  mammary tissue and their inguinal canals are
  open.  Group housed bucks may fight. 
• The rabbit is an induced ovulator and has no
  distinct estrous cycle, although she is typically
  a spring breeder.  The doe ovulates ten to twelve
  hours after mating.  When she is receptive to a
  male, she exhibits a posture called lordosis,
  elevating her hindquarters.
• Gestation in rabbits is 29 - 35 days. 
  Parturition
• ( kindling) occurs in the early morning in a
  nest that the doe makes by plucking fur from her
  dewlap, abdomen and sides. 

33
Sexing

• Differentiating mature males from females is
  fairly easy. As females mature, they develop a
  soft fold of skin below their chin, from which
  they pluck hair when nesting. This is called a
  dewlap. Compare the profile of the female,
  left, with the male at the right.

34
Sexing

• To determine sex by genitalia, gently press the
  skin back from the genital opening and stretch
  the perineum.
• In the male, this procedure will cause the penis
  to be everted.
• The vulva of the female has the appearance of a
  slit. This procedure is necessary when sexing
  young rabbits.

35
Use in research
36
History of the Rabbit in Research

• Rabbits were discovered in Spain in approximately
  100 BC.  They were transported throughout the
  Roman Empire as an easily portable food source. 
• Domestication of the rabbit probably occurred
  when French monks set up walled compounds during
  the 1500s. 
• Rabbits have been used in research for hundreds
  of years.  In the early 1600s, rabbit eyes were
  studied and glaucoma was described. 
• In the 1880s, Louis Pasteur did much of his
  research and testing of rabies vaccine using
  rabbits.

37
List of historical uses

• The cause and treatment of many human diseases
  have been studied using the rabbit as a model.
  Because of its response to different diets, the
  rabbit was the first animal model used to study
  atherosclerosis. Other noninfectious diseases
  studied in the rabbit include osteoarthritis,
  pregnancy toxemia, endometrial adenocarcinoma,
  drug teratogenesis, hydrocephalus, muscular
  dystrophy, glomerulonephritis, and gallstones.

38
List (cont.)

• Infectious diseases studied in the rabbit include
  staphylococcal infection, bacterial endocarditis,
  and Reiter's polyarthritis syndrome. Hereditary
  studies include familial hypercholesterolemia,
  dwarfism, and glaucoma.

39
Syphilis

• There are some diseases of man for which only the
  rabbit can serve as a model. One of these is
  syphilis. The rabbit is the only other mammal in
  which syphilis occurs naturally. The causative
  agent of human syphilis, Treponema pallidium,
  cannot be grown in vitro.
• But we can put the human organism into rabbits
  and study its growth there. If and when a vaccine
  is developed for human syphilis, trials will
  undoubtedly be conducted using the rabbit first.

40
Pet vaccination

• Animals have also benefited from research using
  rabbits. Pasteur developed a vaccine to protect
  dogs from rabies by using dried spinal cord from
  rabbits that had been experimentally infected

41
Analogous systems

• Four other characteristics of rabbits make them
  desirable for specific research tasks.
• First, by analogous systems, we mean that some of
  the rabbit's organ systems are very similar to
  systems in man.
• The rabbit is often the model of choice to study
  immune responses for this reason.

42
Size

• Rabbits may be preferred over other common
  laboratory animals because of their size. They
  have sufficient blood volume to allow for large
  blood samples to be taken either singly or
  serially. Because of their size, they may be
  preferred over rodents for studies that require
  temperature monitoring or surgical procedures.

43
Reasons Not to Use

• Size
• Expense
• Variable response to anesthetic agents
• Prone to cardiovascular failure
• Prone to stress related diseases (ex-coccidiosis)

44
Reproduction study

• A doe has two uteri, each of which opens into the
  vagina through a separate cervix. This unique
  reproductive anatomy allows for an experimental
  group and a control group within a single
  biologic host.
• Rabbits are also useful for studies that require
  precise timing during gestation, as a doe
  ovulates about ten hours after mating, and
  gestation is well defined at 30-32 days.

45
Susceptibility to disease

• The last of these characteristics that make the
  rabbit valuable for specialized studies is its
  susceptibility to spontaneous and induced
  diseases such as syphilis, herpetic
  conjunctivitis, tumors associated with papilloma
  viruses, glaucoma, hyperlipidemia, and
  nutritional muscular dystrophy.