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Biomethodology of the Guinea Pig

·        General Biology

·        Experimental Uses

·        Sources and Ordering

·        Behavior

·        Biological Data

·        Basic Husbandry

·        Identification

·        Handling

·        Sexing

·        Transport

·        Environmental Enrichment

·        Occupational Health /Zoonosis

·        Health Surveillance

·        References

General Biology:

Nomenclature and Breeds

·        The guinea pig, Cavia porcellus , is a mammal of the order Rodentia, sub-order Hystricomorpha ("porcupine-like") and family Caviidae.

·        Three basic breeds of guinea pigs exist. The English (short-haired), Peruvian (long-haired) and Abyssinian which has a rosette hair pattern. Pigmented guinea pigs of all three breeds are also available.

·        Most guinea pigs used in research are "outbred" animals of the various breeds. The common Dunkin Hartley guinea pig (future picture) is an albino outbred guinea pig of the English (short-haired) breed.

·        Several "inbred" guinea pig strains are also available. The "strain 2" and "strain 13" guinea pigs are the most widely used inbred guinea pig strains.

Unique Biological Characteristics

·        Guinea pigs are herbivores and unlike most laboratory animals, except non human primates, they require a nutritional source of Vitamin C.

·        Kurloff cells are unique to the guinea pig. The cell is a mononuclear leukocyte that has round to ovoid inclusions. While the origin and function of the cell is not known, their numbers increase with higher levels of estrogen and the cells migrate to the placenta in pregnant guinea pigs.

·        Guinea pigs have a cervical thymus making it easy to access for experimental manipulations.

·        Guinea pigs are considered to be a steroid resistant species.

·        The ECG of guinea pigs resembles that of humans with easily identifiable P,Q,R,S and T waves. Their T wave is distinctly separate from the QRS complex.

·        The majority of pulmonary stretch receptors in guinea pigs are located in small airways and in pulmonary parenchyma

Experimental Uses

·        Anaphylaxis

·        Histamine sensitivity in acute bronchospasm

·        Reproductive biology

·        Nutrition studies

·        Tuberculosis

Routine Technical Procedures

Blood Collection Sites

·        large volumes – cranial vena cava (terminal only)

·        moderate volumes – jugular vein, saphenous vein, dorsolateral penile vein, retro-orbital

·        small amount – clipping toenail short

Sources and Ordering

·        Inbred and outbred guinea pigs are available from many commercial sources. The DLAR office staff is familiar with many of the commonly available strains and will assist in locating animals available for purchase.

·        Commercially bred guinea pigs from Charles River must be ordered by Tuesday at 9:00 a.m. for delivery on Thursday of that week. Animals should be held for 48 hours before experimental use to allow recovery from the stress of shipping.

Behavior

·        Guinea pigs are very docile and rapidly become accustomed to gentle handling.

·        Guinea pigs rarely bite. Aggression between females is uncommon and is more likely to occur between males in competition for a female in estrous.

·        Fighting is rare - even between males.

·        Guinea pigs are easily alarmed and will often "freeze" for extended periods (30 minutes) when startled. Group housed guinea pigs may stampede when startled which may result in injury to young guinea pigs, orthopedic injuries, and abortion in pregnant dams.

·        The primary interaction between guinea pigs is "huddling". Social grooming is rare. Dominant animals may "barber", or chew/clip the fur of subordinate animals.

·        Guinea pigs are considered crepuscular (most active in "twilight" hours) animals.

·        When placed in a comfortable environment, guinea pigs may be active for more than 20 hours per day.

·        Guinea pigs will eat as long as food is available.

Biological Data

<DIV align=center>

<TBODY>

Adult body weight: male

800-1200 gm1

Adult body weight: female

250-320 gm1

Body surface area

9.5 (wt. in grams)2/31

Life Span

4-5 years2

Food consumption

6 g/100 g/ day1

Water consumption

10 ml/100 g/day1

Puberty: male

8-10 weeks3

Puberty: female

67.8 + (21.5 SD)days3

Gestation Period

65-72 days2

Body Temperature

37.2-39.5 C1

Heart rate

230-380 beats per minute1

Respiratory Rate

42-104 per minute1

Tidal volume

2.3-5.3 ml/kg1

Blood Volume

67-92 ml/kg4 </TBODY>

</DIV>

Basic Husbandry

·        Specific Pathogen Free (SPF) guinea pigs are free from certain bacterial, viral, and parasitic pathogens. To maintain the SPF microbial status animals must be housed in more stringent conditions that prevent the introduction of other pathogens. Examples of housing include isolation in separate rooms or maximum isolation housing.

·        Conventional guinea pigs are not known to be free of pathogens.

·        Most guinea pigs are gang housed in large pens. The pens have hardwood chip bedding on the bottom to collect urine and feces. Water bottles and feeders are affixed to the sides of the pens and are elevated. If feeders are not elevated, guinea pigs will sit in the feeders and urinate and defecate in them, contaminating the feed.

·        Some guinea pigs are singly or group housed in stainless steel cages on raised slatted floors. Wire flooring is not recommended because it can cause pododermatitis ("sore hock") which is inflammation and infection of the foot pads. This condition occurs because guinea pigs are relatively heavy in proportion to the size of their feet.

·        The husbandry staff change cages twice per week. Water bottles and feed hoppers are checked daily by the caretakers to insure the provision of water.

·        Some guinea pigs learn to play with the water bottle and will drain the bottle. Investigators should check the water bottles when they are in the room and bring any empty or low water bottles to the attention of the husbandry staff.

·        Feed is provided daily. Pelleted natural ingredient diets are used to feed all rodents and are composed primarily of cereal grains which are supplemented with additional protein, vitamins and minerals. Due to the nature of this type of diet the exact composition can vary substantially from each vendor.

·        Guinea pigs are one of the few mammals other than primates that require a nutritional source of Vitamin C. For that reason guinea pig chow is has a shorter shelf life (90 days) than standard rodent chow and is manufactured specifically for guinea pigs.

·        Housing parameters:

-         Room temperature - 64-70 F

-         Humidity - 30-70%

-         Ventilation - 10-15 air changes per hour

Identification

·        Cage cards are utilized to identify the strain of guinea pig, sex, number, principal investigator, and IACUC protocol number.

·        Cage cards should not be removed from the cage/pen to avoid misidentification of the animals.

·        Temporary identification of individual animals can be accomplished by dyeing the fur or clipping the hair. Various dyes such as trypan blue, picric acid, fuschein or methyl violet can be utilized. This form of identification will last only 1-2 weeks.

·        Permanent forms of identification can be achieved by the use of ear tags, ear punch or ear notch. Fighting between cage mates will result in the occasional loss of an ear tag.

·        Toe clipping is not a recommended form of identification.

·        Colored guinea pigs can be individually identified by noting the pattern of coloration.

Handling

·        When handling guinea pigs it is advisable to wear latex gloves to prevent the development of allergies.

·        Guinea pigs seldom bite but are timid or easily frightened and usually make determined efforts to escape when held. Guinea pigs typically become accustomed to repeated handling.

·        To pick up a guinea pig one hand should be gently placed dorsally over the thorax or ventrally under the thorax and the other hand should be used to support the animals hindquarters. Care should be taken not to apply to much pressure over the thorax to avoid damaging the viscera or compressing the lungs thereby compromising respiration.

·        Special care should be exercised in supporting the lower part of the body of pregnant females since they may become very heavy and awkward in late pregnancy.

·        After grasping the guinea pig secure the animal by wrapping it in a towel or holding it against your body to decrease struggling.

·        Do not attempt restraint by solely grasping the skin. The lack of loose skin in guinea pigs will result in hair depilation if this technique is utilized.

·        Neonatal guinea pigs can be handled from the day of birth.

Sexing and Reproduction

·        A female guinea pig is called a sow. A male guinea pig is called a boar.

·        Male and female guinea pigs can be differentiated by palpating the penis or extruding the penis of the male by gently applying pressure above the urethral orifice. This technique will expose the vaginal membrane, which in females closes the vagina unless the guinea pigs is in estrous or about to deliver young.

·        The anogenital distance is similar in males and females and cannot be used for sex determination.

·         Gestation in guinea pigs is 58-75 days. Labor is short. Parturition may occur at any time of the day.

·        Young are precocial (eyes open, fully haired) and will usually be walking, eating and drinking by one day of age.

·        The young are weaned at 3 weeks of age.

Transport

·        Guinea pigs that are moved indoors can be transported in a rat cage. A clean rat cage can be obtained from the cage wash area and filled with one half inch of bedding material. If you cannot locate a clean cage, ask a supervisor or caretaker in the area for assistance.

·        A wire bar lid should be placed over the cage to secure the animal during transport. If the animal is going to be in the laboratory for more than an hour a water bottle should also be obtained.

·        During transport the water bottle should be placed upright in the cage lid to prevent spillage.

·        Transport always results in some stress to the animal, however, animals should recover from indoor transport within their own cage within an hour. No recovery time may be needed if the animals are moved with care and have become accustomed to routine transport.

·        It is recommended that a permeable drape be placed over the cages to darken the cage and prevent over-arousal of the guinea pigs during transport.

·        Only DLAR husbandry or veterinary staff members can transport guinea pigs 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.

Environmental Enrichment Opportunities:

·        Group housing is the main form of housing for guinea pigs in DLAR. This allows social interaction.

·        Handling by personnel is important and increases the ease of working with these animals.

·        Food/chewing items can be made available such as wood chew sticks and vegetable treats.

·        If animals cannot have environmental enrichment opportunities because of the nature of the research, please contact the DLAR Director or the Clinical Veterinarian (444-2194).

Occupational Health /Zoonosis:

·        Occasionally personnel may be scratched by a toenail when handling the animal. Personnel may also receive a puncture wound from the cage equipment. As always, it is important to clean the wound promptly and seek medical attention if appropriate.

·        A tetanus vaccination is required for all personnel working with animals.

·        Allergy to guinea pig 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.

Health Surveillance

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 any experimental manipulations performed

-         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.

·        References

1) Harkness JE, Wagner JE. The Biology and Medicine of Rabbits and Rodents ; 3rd Edition, Lea and Febiger, Philadelphia, PA, 1989.

2) The UFAW Handbook on the Care & Management of Laboratory Animals, 6th Edition; Editor Poole, TB. Longman Scientific & Technical, England, 1986.

3) Wagner JE, Manning PJ. The Biology of the Guinea Pig; Academic Press, 1976.

4) Joint Working Group on Refinements. Removal of blood from laboratory animals and birds. Lab. Anim. 27:1-22,1993.

5) Assistant Laboratory Animal Technician Manual, American Association for Laboratory Animal Science, Memphis, TN, pgs. 119-120, 1999.

6) Terril LA, Clemons DJ. The Laboratory Guinea Pig, CRC Press, Boca Raton, NY, 1998.