Rabbits

Rabbits
Rabbits 2016-04-14T13:05:15+00:00

Rabbits

ALL PETS VETERINARY CENTER
1219 Dorsey Lane
Louisville, Ky 40223
502-384-0551

Missy Jewell, MS, DVM

Biology and husbandry:

Rabbits are not rodents, they belong to the family Lagomorph, along with hares and pikas.  They differ from rodents by the presence of 2 small additional upper incisors called “peg teeth” that are situated behind the major upper incisors.  Domestic rabbits come in a variety of breeds from the tiny Dwarfs at 2.5 pounds all the way to the French Lop at 24 pounds.  Most rabbits are gentle and quiet and have distinct personalities, but all are capable of kicking, scratching and biting if they become threatened or anxious.  Rabbits have extremely powerful hind limbs and can injure not only you, but themselves if handled improperly.  A rabbit’s back quarters must ALWAYS be supported when picking them up.  A kick in midair can be strong enough to hyperflex and fracture a vertebrae resulting in a paralyzed animal.  A good trick for calming nervous rabbits is to “hypnotize” them by placing them on their backs in your arms like a baby.  When held this way, they fall into a sort of trance.  Be careful, however, if not supported securely they can “awake” suddenly and jump from your arms.  A rabbit should NEVER be lifted by its scruff or its ears.

Wild rabbits dig for a living making burrows, uprooting food, etc., and their nails are worn down naturally by this activity.  Pet rabbits do not have opportunity to dig and special attention must be paid to keeping their toenails trimmed to an appropriate length.  Excessively long nails can break, causing painful wounds, they can cause abnormal weight bearing on the bottoms of the feet and result in sores on the hocks, and they can cause angular deformity of the toes causing painful arthritis.  Nails should be trimmed every 3-4 weeks.

Rabbit’s teeth grow continually throughout their lives.  Proper alignment is necessary to keep the teeth worn down in a normal fashion.  Sometimes, due to poor diet, genetics or illness, the incisors (front teeth) or cheek teeth (molars) get out of alignment and will result in overgrowth of teeth with sharp points that damage the cheek or tongue.  ONLY in these instances do the teeth need corrective trimming.  Most rabbits will never need this procedure.  Corrective trimming of teeth should NEVER be done with nail clippers or any type of cutting/crushing instrument.  These tools can cause the tooth to crack or shatter, possibly into the live root area leading to severe pain and infection.  Any tooth trimming should be done with a high speed grinding wheel or dental bit while under sedation.

To ensure proper wear of teeth naturally, a rabbit’s diet must contain adequate roughage in the form of hay or leafy greens.  The long stem fiber found in these food items is also critical to normal function of the intestinal tract. Pelleted food was designed for the research, fur and meat industry as an easy means of feeding rabbits that were not expected to live very long.  It provides high quantities of nutrients with minimal chewing effort, thereby promoting heavy weight gain and ineffective tooth wear.  Rabbit’s do not process simple carbohydrates well either, so foods high in sugar should be avoided or severely limited.

Just as a rabbit’s teeth are constantly growing, their intestinal tracts are in perpetual motion.  The rule is…FOOD IN: POOP OUT ; 24/7.  Any change in a rabbit’s normal food intake or fecal output must be acknowledged as a sign of illness.  A rabbit’s normal fecal production is copious amounts of solid, round, dry looking pellets.  They also produce a special kind of feces, called cecotrophs, (night feces) 2-3 times daily that are darker, softer, moister and clumped together, which should be ingested by the rabbit immediately upon production.  These cecotrophs contain high levels of volatile fatty acids and b-vitamins that are important to the rabbit’s health.  They also contain millions of live bacteria that are crucial to continued normal digestion.  Any indication of fewer, smaller or clumped feces should be cause for immediate concern.  Diarrhea in a rabbit should be considered an emergency.  Abnormal bacterial growth can cause GI stasis, and/or toxin production that could lead to death in as little as 24 hours.  A rabbit’s stomach is never empty, and they cannot vomit.  There is always a gastric mat of food, hair and fluid churning in the stomach.  In addition to proper roughage and fiber, a rabbit needs an unlimited supply of fresh water to keep the whole gastric food mat moist and pliable.  Rabbits like to dump over bowls, so sturdy ceramic crocks or water bottles should be used.  Dehydration in a rabbit is a direct predisposing factor to the development of gastric stasis.  Anything that negatively affects water intake by a rabbit must also be considered an emergency.  Therefore, the basis of treatment for nearly every rabbit patient in the hospital will be centered around re-establishing or maintaining normal GI function and hydration.

Physiologic facts:

Rectal Temperature  100-103 F

Heart rate          150-300

Respiratory rate    30-60/min

Tidal volume    4-6ml/kg

Blood pressure      90-130 mmHg

Dental formula      2-0-3-3/2-0-2-3

GI transit time     4-5 hours

Average lifespan    7-8 years (lg breeds)    10-12 (sm breeds)

Sexual maturity     4-7 months (male)  5-9 months (female)

Gestation       29-35 days

Litter size         4-10

Weaning age     4-6 weeks

Diagnostics:

Many routine diagnostic and therapeutic procedures used for dogs and cats can be easily performed on rabbits with a little patience and practice.  Respiratory rate should be obtained while the animal is still in the carrier or while sitting comfortably on the exam table.  It will be fast.  The heart rate should also be obtained prior to causing any stress, and it will also be fast. The chest cavity of a rabbit is small compared to its body and heart sounds are best heard between the front legs. Temperature can be taken either with the rabbit in normal ventral recumbency or in trance position.  If the rabbit has respiratory issues, it should not be placed in trance position.  The weight should be obtained using an infant or small animal digital scale.

Blood collection can be performed from several sites.  If the rabbit is well tempered, blood can be collected from the jugular with similar restraint to a cat.  Female rabbits (Does) commonly have a large flap of skin and fat under their chin called a dewlap which makes jugular venipuncture nearly impossible.  My choice for blood collection in nervous rabbits is the lateral saphenous vein.  Rabbit veins are small and fragile.  You must have a steady hand and a patient heart to be successful.  Use a small gauge (25-27) needle and a 1ml or 3ml syringe.  Blood can also be collected from the cephalic vein, but if you plan to place an IV catheter or induce anesthesia later, these veins should be saved for that purpose.  With the possible exception of an emergency glucose level, blood should NEVER be collected from the ear veins.  Thrombosis of these veins after venipuncture can lead to necrosis and sloughing of part of the pinna.  Besides, a rabbit’s ears are very sensitive, and I believe this to be unduly painful.   A low glucose level in an anorexic rabbit is an extremely poor prognostic finding as it signals the beginning of toxic shock.

Fecal examination should be done with standard flotation techniques.  However, the high level of fiber in a rabbit’s feces makes reading the slide difficult.  A filtration system should be used if possible to remove bulky debris.  You must scan up and down through several focal planes so as not to miss small parasites.  Coccidia are common, but are commonly confused with a normal fecal yeast called Saccharomycetes guttulatus and should be differentiated.  Tapeworms and roundworms can also be found.

Urinalysis in rabbits is complicated by an exceptionally high level of calcium normally excreted in rabbit urine which makes it cloudy and gritty.  Specific gravity is not useful due to the presence of these minerals.  Normal color can vary from pale yellow to orange or even brownish red that can look similar to blood.  The pH is normally alkaline approximately 8.0-8.2.  Trace glucose and protein can be normal.  Sediment can be examined for bacteria, inflammatory cells, and RBC’s.  Gram stain of urine sediment may identify spores of Encephalitozoon cuniculi.  The presence of ketones in rabbit urine is a poor prognostic sign as it usually indicates onset of hepatic lipidosis in anorexic animals.

Dermatologic lesions can be evaluated using skin scrapings for mites, tape impressions for other parasites, DTM culture for ringworm, and cytology for bacterial or yeast infections.  Ear mites can be found in waxy debris from the ears and usually are associated with severe inflammatory reaction and secondary infections.  This condition is extremely painful and cleaning of the ears should be done very carefully and possibly under sedation.

Radiography is essential to diagnosing and treating many conditions of the pet rabbit.  Good quality radiographs can be obtained of specific areas as well as the whole body without sedation (again with a little patience).  VD views are easy to obtain by placing the rabbit in trance position and moving your hands very slowly into proper positioning.  Lateral recumbency is more of a challenge but can be achieved with two people working together.  Each person places their hands along the sides of the rabbit either next to the shoulders or the hips.  The rabbit is gently placed on its side and the handler’s hands are slowly moved toward the extremities until proper positioning is achieved.  If the rabbit begins to struggle you must release it and start over.  Further restraint of a struggling rabbit can lead to cardiac arrest.  Skull films for evaluation of teeth roots must be made under sedation.  VD, lateral, lateral obliques and AP views are all necessary.

Hospitalized Patients:

If it is necessary to keep a rabbit in the hospital for treatment, there are a few items to address.  The bottom of the caging should have heavy layers of newspaper  and possibly a towel.  You must watch to make sure the rabbit does not chew on the towel and rubber mats should never be placed in with a rabbit.  The urine will leave mineral deposits on steel and laminate cages, but can removed with”Lym-away” if severe.  All rabbits should be provided a box in which to hide and should be kept as far away as possible from sights, sounds and smells of cats and dogs.  Unless instructed otherwise, food and water should be available to rabbits at ALL TIMES.  They do NOT need to fast before surgery because they cannot vomit.

Rabbits placed on IV catheters are usually too sick to cause much problem, but as they recover, they will chew on lines, ports and any wrap on their legs.  Vet-wrap and rabbits do not belong together.  They tend to chew at the material and compress it tighter and tighter until it forms a tourniquet.  All bandage material should be white tape.  E-collars can be used, but I feel it stresses them and reduces their likelihood of normal eating.

Medications can be given through IV catheters, by subcutaneous injection, intramuscular injection or orally.  Rabbit’s skin is VERY fragile.  Shaving should be done extremely carefully.  Subcutaneous injections are usually given in the dorsal skin folds between the shoulders.  Intramuscular injections should be done in the quadriceps (cranial muscle) or biceps femoris (caudal muscle) of the hind leg.  Oral medicating can be easily done with liquid forms.  Occasionally, a tablet or powder must be given and can be crushed and added to applesauce or yogurt.  Rabbits in the hospital setting will frequently require syringe feeding.  A special syringeable formula called Critical Care is available for this purpose.  Vegetable baby food is also acceptable but not as well balanced.  I find most rabbits tolerate syringe feeding best if left in normal ventral position and released to resume chewing.  Occasionally, a rabbit make have to be picked up to be given a mouthful, but should be put down to chew.  They should not be held on their backs while syringe feeding as this could lead to aspiration.

Fecal production is very important in gauging the patient’s response to treatment.  Frequently, we will place a plastic baggie on the patient’s cage and collect all fecal matter every hour to monitor continued output and total production.

Medications:

Because of the rabbit’s specialized digestive physiology, certain medications must be used cautiously and in some instances avoided altogether.  This matter is most noteably illustrated by antibiotic associated diarrhea and enterotoxemia. Some antibiotics have the potential to cause enteritis by selectively killing certain bacteria and allowing pathogenic species to proliferate, such as  Clostridium, E. coli, and Enterobacter.  Oral antibiotics are more likely to cause diarrhea than those given parenterally, but many factors play into the actual effect a given antibiotic has on the rabbit’s system including, stress level, fiber content of diet and even age.  Antibiotics that should NEVER be given by oral route to a rabbit consist of penicillins (Amoxicillin, Clavamox), cephalosporins (Cefa-drops, Cephalexin), clindamycin (Antirobe) and lincomycin.  Penicillins and cephalosporins are safe when given parenterally at recommended dosage levels.  Oral antibiotics that are safe even for long term use include enrofloxacin (Baytril), metronidazole (Flagyl), potentiated sulfas (Albon, Sulfatrim), and azithromycin (Zithromax).  Any rabbit placed on any antibiotic should be monitored for diarrhea and the medication should be stopped if this occurs.

Surgery:

Whatever the procedure that a rabbit may be scheduled for, the first concern must be for adequate pain control.  Pain has a direct effect of slowing down the digestive tract and can lead to anorexia and stasis after a surgical procedure.  Rabbits should NOT be fasted before surgery and should be offered food and water as soon as they are awake enough to hold their head up.  Preventive pain control should start before surgery and continue several days after any procedure that you would consider painful.  Use of several medications together can lower the dose of individual drugs and provide better pain control through synergistic action.

The anesthetic drug of choice for rabbits is Isoflurane.  Anesthesia can be induced with isoflurane but the gas is noxious, and they will hold their breath until they absolutely must breathe.  This breath holding can cause severe bradycardia and lead to arrythmias.  Instead, I prefer to use some kind of IV induction agent that prevents breath holding without prolonging recovery times.  I have found that a combination of ketamine, diazepam and propofol works very nicely.  With some practice, the small dosage can be given IV through the cephalic vein.

Because of anatomical structure, rabbits are very difficult to intubate.  It can be done blindly by carefully listening to breath sounds and advancing a small tube size into the trachea of an already sleeping animal.  Believe me, it’s mostly luck and it cannot be relied on in an emergency.  Tracheal intubation is easily achieved with the use of a small rigid endoscope, however, the cost of such equipment usually precludes their use in most practical settings.  Instead, rabbits are usually maintained on gas anesthetic via a small face mask during surgery.  A small muzzle can be used to hold the cone in place over the nose, but be sure that the mask does not pinch closed the nostrils.  Rabbits are obligate nasal breathers, therefore any gas that enters their nose, gets inhaled into the lungs.  This allows work to be performed in the mouth without an endotracheal tube.  Heart beat should be constantly monitored during anesthesia and can be done with a Doppler probe clipped to the inner ear or with a stethoscope manned by the anesthetist.  Breathing rate and depth must also be constantly monitored during anesthesia as changes occur suddenly and without warning.

Any sutures used to close skin incisions should be buried under the skin because rabbits are fastidious groomers and are notorious for chewing out stitches.  Bandages are likewise chewed off or obliterated, and should not be used in most cases.  Recovery from anesthesia is best done in a quiet area. Rabbits are prey species and certain sounds and smells that are experienced while half awake and confused could cause over excitement leading to thrashing, bolting, or possibly heart arrythmias and death during the recovery period.

Summary:

Until you have lived with a rabbit, it is hard to understand all the subtle characteristics that make them so special.  They are very affectionate, easy to care for and can provide many years of companionship, but they have special needs when it comes to veterinary care.  To disregard any of them will do great disservice to your patient.