Guinea Pig
Cavia porcellus
Biology and Anatomy
Origin
Cavia porcellus –
domesticated
Cavia aperia – wild
Wild – Peru, Argentina,
Brazil, Uruguay
Also known as Cavies
Domesticated 16th
century – England
Uses of Guinea Pigs
Pets
Scientific research
Food
The guinea pig (Cavia porcellus or cavy), is
a docile rodent used in the United States as
a pet and as a research animal
The first reports of domestication of the guinea pig
were around 1530, when Pizarro conquered Peru.
The rodents were used for food and religious
sacrifices.
“CUY CHAQTADO”
A recipe for fried Guinea Pig
Fried Guinea Pig (Ayacucho-style)
1 guinea pig, de-haired, gutted, and cleaned
1/2 c. flour
1/4 - 1/2 t. ground cumin salt and black pepper
to taste
1/2 c. oil
Pat dry the skin of the guinea pig and rub in
the cumin, salt, and pepper. Preheat oil. Dust
the carcass with the flour and place it on its
back in the oil, turning to cook both sides.
Alternately, the guinea pig can be cut and fried
in quarters.
Serve with boiled potato or boiled manioc
root, and a salad of cut tomatoes and slivered
onion bathed in lime juice and a bit of salt.
“Taste like chicken”
“Have some Pisco in hand”
Taxonomy
The guinea pig is in the order Rodentia, the largest
mammalian order, which includes rats, mice and
squirrels.
Guinea pigs are placed in the suborder
Hystricomorpha, along with chinchillas and
porcupines, and in the family Caviidae.
The Caviidae, which include the capybara, are
herbivorous South American rodents characterized
by a stocky body, vestigial tail and long gestation.
Uncle Skeeter
Cousin “Booger”
Erethizon dorsatum
Hydrochoerus hydrochaerus
Aunt Charlene
Cousin “Bubba”
Chinchilla laniger
Octodon degu
Varieties of Guinea Pigs
Traditional
American or English – short hair
Abyssinian – whorls of short rough hair
Peruvian – long hair
Varieties of Guinea Pigs
New varieties
Silky – medium length soft hair
Teddy – short, coarse hair
American Crested – short hair with
contrasting whorl on forehead
Rex – very short, soft hair
Hairless
Traditional varieties of guinea
pigs
The most common pet varieties are the English
Shorthair and the American Shorthair.
The Abyssinian has short rough hair
arranged in whorls or rosettes.
The Peruvian, or 'rag mop' variety, has long silky
hair. Guinea pigs of each variety may be monocolored, bicolored, or tricolored
New varieties of guinea pigs
Silky – soft, medium hair
Teddy – short, coarse hair
American crested – contrasting
whorl on head
Rex – very short, soft hair
Hairless – (well, almost)
Lab stocks-outbred
In the laboratory, the stocks include the
Hartley, also known as the Dunkin-Hartley, an
outbred shorthair albino; the NIH Outbred, a
multi-colored guinea pig; and the hairless,
euthymic guinea pig.
Basic Guinea Pig
compact stocky body
tailless
diurnal – actually
short naps night and day
sebaceous marking glands - rump
open rooted teeth
Additional characteristics
vocalize – at least 11 sounds
http://www.guineapigs-online.com/html/piggiesounds.html
good swimmers
seldom jump
rarely bite or scratch
need frequent handling
lifespan – 4- 5 years
Group housed guinea pigs establish maledominated hierarchies. This is often expressed by
circling and vocalizations.
USES IN RESEARCH
According to the U.S.
Department of Agriculture, in
1990 approximately 350,000
guinea pigs were used in
research, teaching and testing.
This number is in contrast to the
estimated number of mice and
rats used annually, which is 10
to 20 million.
Similarity to humans
Guinea pigs have anatomical and physiological
features that make them excellent models for
specific studies. Guinea pigs and humans share
several features, including a need for dietary
vitamin C, similar placentation and hormonal
control of pregnancy, delayed hypersensitivity
reactions, and susceptibility to tuberculosis.
Other research uses
Other research uses of the guinea pig
include immunological studies, for which
they are a source of serum complement;
auditory research; teratology and toxicity
research;
The guinea pig is also being used as a
model for spontaneous diabetes mellitus
ANATOMY AND PHYSIOLOGY
Guinea pigs have 7 cervical, 13-14 thoracic, 6
lumbar, 2-3 sacral and 4-6 coccygeal vertebrae.
Vertebral formula:
C7 T13-14 L6 S2-3 Cy4-6
Dental formula
Guinea pigs are monophyodont, that is, they get
one permanent set of teeth. Their dental formula
is unique for rodents, as most rodents do not have
premolars. All the teeth are hypsodont, or open
rooted.
Dental formula:
2(I 1/1 C 0/0 PM 1/1 M 3/3) = 20
Digits
Guinea pigs have four
digits on the forelimbs
and three digits on
their hindlimbs.
Ears
The ears of the guinea pig
are small and access to the
veins is difficult. Guinea
pigs have large tympanic
bullae and the internal
structures of the ear are
easily reached features that
facilitate auditory research.
TEATS
Both the male and
female have teats.
The female has a
single pair of
inguinal mammary
glands.
The thymus
The thymus of the
guinea pig surrounds
the trachea. This is in
contrast to rats, mice
and other murid
rodents, in which the
thymus is deep within
the thoracic cavity,
overlying the heart.
The adrenal glands
The adrenal glands are
bilobed and large
compared to most rodents.
They are situated cranial
to each kidney. In this
image, in which the
animal's head is to the left,
the kidney is obscured by
renal fat, but the left
adrenal gland is indicated
by an arrow.
Gastrointestinal
Guinea pigs are
monogastric, but they
have a lower intestinal
tract typical of herbivores.
The large intestine
occupies most of the
abdominal cavity, and the
cecum, identified by the
arrow, contains up to 65%
of the total gastrointestinal
contents.
Vaginal closure
The female guinea pig
(sow) can be distinguished
from the male by a
shallow, U-shaped break
in the ridge between the
urethral orifice and the
anus. This break is
covered with a vaginal
closure membrane which
is only open during estrus
and parturition.
Which one is the male?
Everted Penis
Sexing is more easily
accomplished by applying
gentle pressure to evert the
penis of the boar, or male.
The mature boar has extraabdominal paired testes,
which lie in the scrotal
pouches and open inguinal
canals.
Penile style
The os penis, or baculum,
is found within the dorsal
surface of the entire length
of the glans. The
intromittent sac, unique to
hystricomorph rodents, is
in the ventral aspect of the
glans. When the penis is
erect, the intromittent sac
everts, revealing two
keratinaceous, horn-like
styles attached to its
caudal end.
Female and male reproductive tracts
The male guinea pig, on the left, has large vesicular glands,
shown by the larger arrow, that are bilateral, smooth and
transparent. These may be mistaken for the uterine horns
of the female, which are identified by the smaller arrow on
the right.
Physiologic values
Normal body temperature of the guinea pig
is 99.0-103.1 F and the average life span
is four-five years.
Respiratory rate is 42-104 per minute
The heart rate is 230-380 beats per minute.
Adult body weight for the sow is 700-900
grams and, for the boar, 900-1200 grams.
Page 154
Physiologic values cont..
Puberty 45-70 days
Breeding age 3-4 months
Gestation period 59-72 days
Litter seize 2-5 pups
Weaning age 14-21 days
Unique future
Guinea pigs are the only rodents known to
require a source of vitamin C in their daily
diet. This is because they lack Lgulonolactone oxidase, an enzyme required
for the synthesis of vitamin C.
REPRODUCTION
Sow and Boar
The sow is a nonseasonal, continuously
polyestrous breeder, with an estrous cycle of 1517 days. The sow also exhibits a fertile estrus
approximately 12-15 hours postpartum.
Usually the sow is bred at two-three months of
age, which corresponds with a body weight of
350-450 grams. A sow should be bred for the first
time before 7 months of age.
For the boar, age at first breeding is typically
three-four months (600-700 grams body weight)
Placentation
Placentation in the guinea pig is discoid and
hemomonochorial. Gestation is between 59
and 72 days, with an average of 68 days;
gestation length varies inversely with litter
size.
discoid placenta
a placenta in which the chorionic villi are arranged in a circular plate
as in human and rodent placentae.
hemochorial placenta
a type of placenta in which all maternal layers are lost so that fetal
tissue is in contact with frank maternal blood, as occurs in
insectivores, rodents, rabbits and most primates.
Handier w/sow
In late gestation,
abdominal distention is
obvious and body weight
may nearly double. The
pubic symphysis begins to
separate in the last half of
gestation due to increased
production of relaxin. The
diameter of the separation
48 hours prepartum is
approximately 15 mm and
may be as large as 22 mm
at parturition.
When are
you due?
Within 24 hrs!
Hey doc, can’t you at
least wear a glove?
Newborns
A litter of two to five piglets is
born within about 30 minutes,
with 3 to 7 minutes between
births. Each newborn weighs
between 60 and 100 grams, with
individual birth weights inversely
proportional to the litter size
Care of Young
precocial – born
furred, eyes open, teeth
erupted
walking within 2 hours
two nipples – inguinal
region
can care for four young
litters 3-4 (range 1-6)
Identification
Guinea pigs may be
identified individually.
Permanent methods
include color pattern
records, ear notching,
microchip, and tattoos.
An ear tag, as shown
here, is another
acceptable
identification method
Resources
LABORATORY ANIMAL MEDICINE AND SCIENCE SERIES II
GUINEA PIGS:
Biology and Use in Research
V-9023
L. J. Tambrallo, DVM, MS
R. E. Fish, DVM, PhD
Office of Laboratory Animal Medicine
University of Missouri
Columbia, Missouri