HAMSTER

HAMSTER

Pornchai Sanyathitiseree

Dept. of medicine

Introduction
Reproduction
Behavior
Diet
Housing
Restraint of Hamsters
Preanesthetic preparation
Disease

Hamster

Order Rodentia

Family Cricetidae

Mesocricetus auratus

There are over 20 species of hamster; the most commonly kept as a pet is the golden ( Syrian ) hamster. Some golden hamster mutants kept as pets are the ruby-eyed , the long haired , teddy(toy) bear and hamsters of different-colored coats.

Advantage to using hamsters in research

Short reproductive cycle and life span
Relative freedom from spontaneous disease
Susceptibility to experimentally induced disease
Acceptance of transplanted tissue and tumors because of its weak histocompatibility antigens.
Disadvantage to using hamster in research

Unpredictable and frequently aggressive behavior makes them difficult to handle.

Hamster urine is cream colored and turbid due to crystalluria and pH is 8.0. Hamsters have a pouchlike area anterior to the stomach which contains microorganism similar to those found in ruminants and their utilization of dietary nitrogen is more like that of ruminants.

The incisor teeth are nonrooted and grow continuously. The molars are rooted and do not grow continuously like the incisors.

Average life span	18 - 24 months
Gestation period	15 - 16 days
Average litter size	6 - 8 pups
Weaning at	20 - 25 days
Estrous cycle	4 days
Temperature	98 - 99 F
Weight	85 - 150 grams
Respiratory rate	35 - 135
Heart rate	250 - 500 bpm

Reproduction

Sexual maturity is reached at about 2 months of age. Although hamsters may show evidence of sexual activity as early as 30 days of age, they are usually not bred until they rerach 60 days of age. Females in estrous usually exhibit lordosis ( a downward arching of the back with the tail pointed straight up in the air). Estrous usually occurs in the evening.

Breeding : Take the female to the male ;remove the male from the female immediately after copulation. The hamsters must be watched to ensure that the female does not attack the male , since the female is the more aggressive of the species and may injure or kill the male. Breeding usually occurs in the evening. In the home where pet males and females are housed together , breeding occurs spontaneously.

Newborn hamsters are hairless atv birth and have their eyes closed. The weaning age of hamster is 28 days. The sex of weanlings can be determined by comparing the anogenital distance. The distance is greater in males than in females. When viewed from above , the adult male posterior looks round because of the protrusion of the testicles , whereas the adult female’s posterior appears square. Also the caudal end of female hamsters is more pointed than that of males.

Mothers will frequently cannibalize their first littter.

Do not handle the young during the first 7 days life.

Hamsters will start eating solid food at 7 - 10 days old. Weaning is complete at 21 - 25 days of age. Youngsters that are fed a varied diet from an early age are less likely to get digestive upsets later in life.

Male hamsters often cannibilize the young and female hamsters may aggressively attack the male to protect her young. Remove the babies at three weeks of age from their mother to prevent injury or death.

Care must be taken if the hamster is asleep in its nest as it is likely to be bite if startled. Hamsters are very short-sighted and may bite in defence if they do not recoghise the approaching hand.

Behavior

Crepuscular animals ( Active at dawn and dusk ) Nocturnal and solitary animal with sensitive to noise disturbance.

Males are usually more docile than females and they make better pets.

Docile unless surprised or awaken. If awakened suddenly out of a deep sleep and handled , the frequently bite.

Curious by nature.

It resembles a miniature bear and combines the hoarding habits of a squirrel with the acrobatics of a monkey. On each side of its face the hamster has a greatly distensible pouch , within which large amounts of food can be stored.

Hibernate when temperature drop below 5C ,however, animal is responsive to external stimuli. This appears to be a state of deep sleep. The hibernating hamsters will curl up in a ball and may look dead. Unlike other hibernating species , hamsters do not build up fat reserves before hibernation; if they do not awaken periodically to replenish their energy supply , they may strave to death.

Escape artists -well ( escapologist ) secured cages are mandatory.

With regard to the social environment of domesticated hamster , it is difficult to keep more than one hamster in the same cage because of fighting. It is possible to maintain animals of one sex from the same litter together but generally they are best kept alone.

House in separate cages. Occasionally hamster will do less fighting if housed together before sexual maturity.

Male hamsters carry out territorial scent-marking using glands on the costovertebral area which can be seen as area of dark pigmentation and coarse hair.Excessive cleaning of cage may not only cause direct disturbance stress but may also disrupt territorial marking.

When breeding hamsters one must observe the male and female closely and separate them if a fight breaks out.

Avoid disturbing female with newborn young - she may stuff babies into her cheek pouches , along with food , bedding or other objects. The young may suffocate in the pouches.

They are generally need to be kept alone to prevent fighting , can inflict a painful bite and have well developed gnawing capabilities which may lead to escape.

Hamsters are very sensitive to loud noise , odor , changes in bedding and the proximity to other animals , especially rats. When housed in the same room with rats , they frequently will not breed.

Diet

Hamsters are excellent hoarders and they possess elasticated cheek pouches in which they can carry large quantities of food and bedding. They are best fed once daily in the early evening , before they peak of activity. The food should be provideed in a hopper or heavy dish to prevent spillage and faecal contamination.

Hamsters differ from other rodents in having a well defined forestomach in which preliminary fermentation occurs. This enhances the breakdown of proteins and carbohydrates but generally increases the requirement for minerals and vitamins.

Compared to the rat , the hamster has a higher requirement for zinc , copper , and potassium.

In their natural state hamsters eat earthworms and mealworms.

Dry food - Proprietary hamster mixes contain mixed corn , maize , alfalfa , dried peas , sunflower seeds and peanuts.

Peanuts are cvery high in protein and an excess may lead to coat changes and digestive disturbances.

An excess of sunflower seeds may lead to obesity and calcium deficiency.

Often times rat feed is used as a basic diet and is then supplemented with rabbit chow or other similar diets.

Hamsters are generally assumed to have similar dietary requirement to other small rodents such as rats or mice or to be suited to a combination of rat and rabbit diet.

Commercial rodent diets containing seeds should be avoided because hamsters tend to eat the seeds rather than the pellets , thereby consuming an unbalanced diet.

Feed comercial rodent/hamster pellets with at least 16 - 24 % protein , carbohydrate 60 - 65 % and fat 5 - 7 %.

-Soybean meal provides a better protein supplement than fishmeal at about 16 % of the ration.

-Protein levels of 18 - 24 % promote more rapid growth but at the cost of higher incidences of nephritis.

Green food

In adults the feeding of green food is useful in preventing obesity.

Green food must be fed dry because wey green food will result in an increased water intake and subsequent loose feces.

Hamsters prefer to eat from the cage floor.

Fresh food should always be available because when the body temperature drops to one or two degrees above the ambient temperature and heart and respiratory rates decrease so as to become almost imperceptible , if ambient temperatures increase a hibernating hamster will wake up rapidly.

Apples and lettuce have been reported to be effective in reducing the incidence of canabalism of babies.

Softened pellets may be offered to babies < 3 weeks old.

Do not feed seed-type "pet" mixed as they do not provide adequate nutrition for growth and reproduction.Hamster may pick out few seeds he likes and stockpile or bury the rest.

Checked bedding , neat daily to remove uneaten food. Females with litters should have the food placed directly on the cage floor- young start eating and drinking at 7 - 10 days of age. It is important to ensure that at this age the baby hamster can reach the water.

Coprophagia in the adult is normal , aids digestion , and supplies vitamin B and K produced by gut microorganism. The redigestion of these fecess satisfies the requirement for vitamin B and K.

Housing

The basic caging requirements of sufficient space , privacy , warmth and opportunities for activity in an easily cleaned environment hold true for hamster. The material used for cages need to be without sharp projections and not liable to splinter , robust (escape-proof) and should enhance warmth by being a poor thermal conductor.

Cages should not be too tall because the hamster can readily fracture limbs if it falls.

An exercise wheel should be provide , the solid type is preferred because there is is less risk of injury. Wheel sold for mice are too small for hamsters and will lead to fur rubbing. If exercise is limited the hamster may appear stiff and reluctant to move. This condition is termed cage paralysis.

Cages must be cleaned weekly. As the hamster is a habitual hoarder , the store of food must be checked daily and anything that is damp or mouldy removed. Hamsters may often reserve one corner of the cage for toileting and this should be cleaned daily.

Space requirements :

Hamster < 60 gm. 10 s.q.in.
Hamster > 60 gm. 11- 20 s.q.in.
Hamster with litters 150 s.q.in.

Hamsters require suitable bedding material as a substrate to absorb moisture and require nesting material in a secluded area of the cage for sleeping during the day;this is of particular important if breeding is intended. Suitable materials include hay , shredded paper , sawdust , wood shavings or cellulose wadding. Cotton-wool should not be used because of the risk of constipation and care should be taken with any material comprising strands.

Pregnant animals will use soft paper for nest building.

Bedding should be replaced 1 or 2 times weekly and can be left as long as 2 weeks when is desirable to leave a litter undisturbed.

A 12 : 12 light/dark cycle is adequate , with 14 hours of phoitoperiods required for breeding colonies.

Hamsters are more adaptable to cold extremes than to warm extremes.

Prolonged room temperatures of less than 55 F may induce a hamster to seek refuge in his nest and sleep until it warmed up. This is not true hibernation , and is not recommended.

Restraint of Hamsters

Hamsters may bite if roughly handleed startled , injured or abruptly awakened or disturbed from a sound sleep.

In handling hamsters and administering treatment , they can be restrainted in several ways.

1. By cupping the hands around them

2. By scooping them into a thin can or paper cup

3. By grasping as much skin as possible over their shoulders

4. By grasping them with the hand facing the rear of body.

5. By placing the thumb and the index fingers around the neck , with the remainder of the fingers around the thorax.

Scruff -of the neck grip for picking up and restraining hamster. Because of the cheek pouches , a hamster has ample loose skin about the neck.

Mortality has been reported after oral or parenteral use of many antibiotics including

Penicillin Ampicillin Vancomycin Erythromycin Cephalexin Lincomycin Cefoxitin Cephalothin Carbenicillin Clindamycin Streptomycin Neomycin Tetracycline Chloramphenicol Gentamicin

Dihydrostreptomycin administration causes fatal ascending paralysis.

Hamsters are generally very resistance to diseases and have few health care problems.

Preanesthetic preparation

Preaneastic stravation is unecessary because regurgitation cannot occur due to the anatomy of the cardia of the stomach. Water should also remain available as any restriction can exaggerate the metabolic effects of anaesthesia.

Premedication; Atropine 40 mcg/kg

Anesthesia; Ketamine (60 - 80 mg/kg) and xylazine (10 mg/kg) IM improve degree of relaxation

Ketamine 40 - 150 mg/kg IM

Pentobarbital (60 mg/ml) 90 mg/kg IP 30 mg/kg IV

Even when an injectable anaesthetic is used it is recommended that oxygen should be administered thgrought the face mask during the operative procedure.

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