Biomethodology of the Guinea Pig
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.
Inbred and outbred guinea pigs are available from many commercial
sources. Vivarium
personnel are familiar with many of the commonly available strains
and will assist in locating animals available for purchase.
To order
animals the investigator must provide the UC Riverside Animal Use
Protocol number.
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 gm5 |
| Adult body weight: female |
250-320 gm5 |
| Body surface area |
9.5 (wt. in grams)2/35
|
| Life Span |
4-5 years21 |
| Food consumption |
6 g/100 g/ day5 |
| Water consumption |
10 ml/100 g/day5 |
| Puberty:male |
8-10 weeks33 |
| Puberty:female |
67.8 + (21.5 SD)days33 |
| Gestation Period |
65-72 days21 |
| Body Temperature |
37.2-39.5 C5 |
| Heart rate |
230-380 beats per minute5 |
| Respiratory Rate |
42-104 per minute5 |
| Tidal volume |
2.3-5.3 ml/kg5 |
| Blood Volume |
67-92 ml/kg34 |
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.
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