Rabbits are not in the order Rodentia but in the order Lagomorpha since they have an additional pair of incisor teeth directly behind the prominent pair in the upper jaw, which is not found in rodents. Rabbits have found wide and varied use in biomedical research. Not only are they used as models of disease, they are also used for serum antibody production, drug screening and to study atherosclerosis. The New Zealand white rabbit is the most commonly used breed in research.
Temporary methods of labeling rabbits include the use of water-proof pens and writing in the ear or on the back of the rabbit. Permanent methods include tattooing or the use of an ink or dye. Cage cards should also be used.
Handling and Restraint
Rabbits are characteristically timid and excitable. Occasionally they resist handling endangering themselves and their handlers. Gentle but firm manual restraint often causes the rabbit to relax and stop struggling. In an attempt to escape they may accidentally scratch the handler or kick their hind legs hard enough to break their own back.
To remove a rabbit from the cage, grasp the scruff of the neck with one hand and support the hind quarters and back with the other. (Figure 4) This helps prevent the rabbit from kicking with its powerful hind legs. Failure to support the rear end can result in injury to the handler and the rabbit.
When carrying a rabbit its head should be tucked into the crook of the arm that is supporting the hindquarters. (Figure 5) Rabbits should never be restrained by grabbing the ears since this can cause painful damage to the ear cartilage. A plastic or stainless steel restraining device or a canvas bag can be used for restraint. This type of restraint is often used when access to the ear is required for bleeding, intravenous injection, tattooing or treatment. The restraining device should be of the appropriate size for the rabbit and one should avoid having the rabbit struggle in them since this could result in spinal injury. For this reason an animal should never be left unattended in a restraining device and should always have its rear limbs firmly controlled.
Body temperature: 100.4° -104° F (38° -40° C)
Heart rate: 130-325 per minute
Respiratory rate: 30-60 per minute
Weight: Adult: 2-6 kg; newborn, 30-80 grams
Water consumption: 100-600 ml per day, or 50-100 ml per 1 kg body weight daily
Food consumption: 100-300 grams per day, or 50 grams per 1 kg body weight daily
Feces: Round pellets. Rabbits also produce stool called night feces which is very soft and covered with a thick mucus. This is a normal part of the animal’s digestive process and the animal eats this stool to recycle protein, water and vitamins. Eating stool is termed coprophagy and is common in rodents and rabbits although only the rabbit produces a special stool for this purpose.
Urine: Can vary in color from clear red or yellow to a milky yellow. High amounts of mineral in the urine account for this color.
Life span: 5-8 years
Sexing and Breeding
A male rabbit is called a buck and a female is called a doe. A buck has an obvious external scrotum that contains the testicles. The sex of young rabbis can be determined by examining the urogenital region. The vulva of a female may be seen as a pointed slit and the prepuce of a male appears as a round, doughnut-shaped opening. Rabbits are polygamous animals. The buck is capable of mating with many females. A doe is taken to the buck’s cage for breeding since does are territorial.
Female rabbits do not have a true estrous cycle. They do have certain rhythmic periods during which they are receptive to the bucks, but the length and frequency vary between breeds. The doe does not ovulate until after mating has occurred (induced ovulation). Rabbits need some form of nest box in which to give birth. The babies are born blind, naked and helpless.
Sexual maturity: 4-6 months
Estrous cycle: No regular cycle although females are usually receptive to breeding at 4-6 day intervals: Induced ovulator
Gestation: 29-35 days
Litter size: 4-10
Cannibalism: Does with new litters, especially first-litter animals should not be disturbed to prevent them from killing their young.
Weaning: 4-6 weeks, but baby rabbits begin eating dry food at about 3 weeks of age
Rabbits are active curious animals that spend a lot of time exploring objects in their environment. One should be sure to secure cage doors and cage cards or the rabbit may try to escape or destroy the cards. Rabbits normally sit on all four feet, with their body weight evenly distributed and the head held level with the top of the back. They move around the cage by hopping and sometimes stand on their rear legs. At rest, especially if hot, a rabbit may stretch out on its side or stomach with its head resting on the cage floor.
A frightened rabbit may race around the cage, kicking with its hind legs, or it may cower in a corner. Rabbits are mild-tempered animals. Occasionally, especially when stressed or frightened, they may attempt to bite or jump at a handler. Sometimes a rabbit may show aggressiveness or fear by stomping its hind feet and when injured or extremely frightened a rabbit may emit a high-pitched scream. They are sensitive to noise and may react violently to loud or sudden sounds. Rabbits nails grow rapidly so they must be clipped. Rabbits are more active at twilight than during the day. They eat and drink mostly in the late afternoon and early evening and sleep during the day.
Husbandry and Diet
The optimum room temperature for rabbits is 61° to 72° F. The lower temperature reduces the amount of shedding and subsequent problems with gastrointestinal blockage by hair balls. Rabbits are housed in suspended caging. Cages and accessories should be sanitized at least every other week. Pans should be cleaned three times a week and sanitized every other week. Pans are treated with an acid solution prior to washing to remove urine scale, which is dried urine containing large amounts of minerals.
Rabbits, like rodents, can develop overgrown incisor teeth. The teeth can be trimmed. Water is supplied ad libidum (continuously). Rabbits stop eating when deprived of water. Rabbits should be fed a pelleted diet usually from a hopper-type feeder. They feed by nibbling or gnawing their food. Commercially prepared rabbit diets are balanced for proper nutrition and have a high fiber content. Rabbits tend to overeat if fed ad libidum and thus are usually fed only measured amounts of feed. The adult New Zealand White rabbit only needs about 150 grams daily of a nutritionally balanced pelleted diet for maintenance. This helps prevent obesity, promotes good health and reduces feed waste. One of the first signs of illness in rabbits is loss of appetite. They should normally be waiting at their feeder. It is necessary to keep the rabbit’s nails trimmed.
Most IV injections are given in the rabbit’s marginal ear vein. This can be done with the rabbit restrained in a bleeding box. Intra-muscular injections are usually given in the muscular hindlegs. Subcutaneous injections are easily given into the scruff of the neck. Intra-dermal injections are given on either side of the back. The fur is shaved off for these. Intra-peritoneal injections are given with the rabbit on its back and its hindquarters elevated. The needle should be inserted on either side of the midline posterior to the umbilicus and in the lower quadrants of the abdominal area.
Blood is usually collected from rabbits from the marginal ear vein. The medial artery of the ear is also a good site for obtaining blood. Cardiac puncture can also be used to collect larger volumes of blood. The rabbit should be anesthetized for cardiac punctures and blood can be withdrawn by placing the rabbit on its right side and inserting the needle between the 3rd and 4th ribs on the rabbit’s left side. Alternatively, the needle can also be inserted below the sternum to the left of the xyphoid cartilage at a 45 degree angle.