Office of Campus Veterinarian

Guinea Pig Biomethodology

(Material adapted from the University of Iowa Animal Care Unit)

General Biology

The Guinea Pig, Cavia porcellus, is a mammal of the order Rodentia, sub-order Hystricomorpha and family Caviidae. Three basic breeds of guinea pigs exist. The English (short-haired), Peruvian (long-haired) and Absynninian which has a rosette hair pattern.

Guinea pigs have several unique biological characteristics. Guinea pigs are herbivores and unlike most laboratory animals, except nonhuman primates, guinea pigs require a nutritional source of Vitamin C.

Guinea pigs can be grouped by their microbial colonization: Specific Pathogen Free (SPF) guinea pigs are free from known bacterial, viral, and parasitic pathogens, as opposed to "conventional" guinea pigs, which are not known to be free of pathogens. Both types of guinea pigs are available for purchase. To maintain the SPF microbial status of guinea pigs may require that animals be housed in more stringent conditions that prevent the introduction of other pathogens such as isolation in separate rooms or barrier housing. This type of housing is available at the University of Iowa, though it is typically not required or utilized by investigators.

Guinea pigs can also be categorized genetically. 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. Pigmented guinea pigs of all three breeds are also available. 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.

Behavior

Guinea pigs are very docile and rapidly become accustomed to gentle handling, in fact guinea pigs rarely bite. Aggression between females is uncommon and is more likely to occur between males in competition for a female in estrous. 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. Guinea pigs are considered crepuscular animals.

Biological Data

Adult body weight: male 800-1200 gm 5
Adult body weight: female 250-320 gm 5
Body surface area 9.5 (wt. in grams)2/3 5
Life Span 4-5 years 21
Food consumption 6 g/100 g/ day 5
Water consumption 10 ml/100 g/day 5
Puberty:male 8-10 weeks 33
Puberty:female 67.8 + (21.5 SD)days 33
Gestation Period 65-72 days 21
Body Temperature 37.2-39.5 C 5
Heart rate 230-380 beats per minute 5
Respiratory Rate 42-104 per minute 5
Tidal volume 2.3-5.3 ml/kg 5
Blood Volume 67-92 ml/kg 34

 

Basic Husbandry

Most guinea pigs are housed in shoebox cages composed of polypropylene (opaque) material with a wire bar lid used to hold the water bottle and feed (figure 1). Bedding is placed directly into the shoe box cage allowing the absorption of urine and the animal to burrow and/or den. This type of cage will hold two guinea pigs weighing 350 grams or greater. When removing the lid from this type of cage it is important to remove the water bottle to prevent spillage. If the cage is to be transported the bottle should be turned sipper tube up to prevent spillage during transport (figure 2). However, you should remember to turn the bottle back over to allow access to water after transport. The caretaking staff, change the cages twice per week, thereby providing the animal a clean cage with new bedding, food and water. Water bottles and feed hoppers are checked daily by 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 caretaking staff. The water provided to animals is chlorinated tap water.

The wirebar cagetop holds the animal feed preventing contamination with urine or feces. 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.

Identification

Cage cards are utilized to identify the strain of guinea pig, sex, number, principal investigator, and research protocol. Cage cards should not be removed from the cage 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. A more permanent form of identification can be acheived by the use of ear tags. However, fighting between cagemates 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 securing it by wrapping in a towel or holding against your body will lessen the frequency of struggle. 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.

Breeding

Guinea pig colonies tend to be very labor intensive and are discouraged for the production of commercially available guinea pig strains. For strains not available commercially or in instances where neonatal or fetal animals are required breeding colonies are occasionally maintained. Investigators requiring the establishment of breeding colonies should consult with the Animal Care Unit to assure proper management of the colonies. Breeding animals have different nutritional requirements, which if not provided, will have a detrimental effect on reproductive performance. Light cycles are important in breeding rats and are provided with 12 hours of light and 12 hours of dark. Deviations from this cycle will effect reproductive performance.

Sexing

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 in females which close the vagina, unless the guinea pigs is in estrous or about to deliver young. The anogenital distance is similar and cannot not be used for sex determination

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 bedded 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. Guinea pigs cannot be transported out of doors or by vehicles by other the vivarium personnel. Investigators can request transfer to other buildings by contacting the appropriate vivarium staff