Guinea Pig Biomethodology
(Material
adapted from the University of Iowa Animal Care Unit)
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.
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.
| 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 |
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.
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.
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.
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.
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
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