THE GUINEA PIG:
BIOLOGY, CARE, IDENTIFICATION,
NOMENCLATURE, BREEDING, AND
GENETICS
Ron Banks
USAMRIID Seminar Series
17 February 1989
NOTE: A shaded statement indicates that an ACLAM boarded
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I.
INTRODUCTION
A.
History and Origin
1.
Origin of the guinea pig is unclear.
a.
Wild guinea pig is Cavia aperea
b.
Widely distributed in Argentina, Uraguay, and
Brazil
c.
Cavia cutleri is still wild in Peru
2.
Spanish found Andean Indians had domesticated
Cavia cutleri
a.
Used as food and for religious sacrifices
b.
Used for food around Spanish Colonial Empire.
3.
Paintings such as the last supper have included
the guinea pig as main course meal.
4.
Guinea pigs are often apartment reared in Peru
today.
5.
1500's: Dutch sailors introduced the guinea pig
into Europe.
6.
1770's: Probably reached the United States as
pets and fancy animals.
7.
Origin of "guinea pig" name is vague.
used by fanciers is "cavy".
Common name
a.
Does resemble a suckling pig
b.
Is prepared for eating by scalding/scraping
c.
Some suggest "guinea" was derived from the
fact that trading ships may have travelled
via Guinea in West Africa, or via Guiana
d.
Adult females called sows, and adult males
called boars. Parturition referred to as
farrowing.
B.
Taxonomy
Kingdom - Animal
Phylum - Chordata (with notochord and gills)
Subphylum - Craniata (Vertebrata): Chordates with
organized head region
Class - Mammalia (Warm-blooded craniates with hair
coat. Young nourished from mammary glands)
Subclass - Theira (Viviparous Mammals = Live
Young)
Infraclass - Eutheria (Placental mammals, versus
Metatherial marsupials, and
Protherial egg layers)
Order - Rodentia (single row of upper and
lower paired incisors which grow
continuously; no canine teeth)
Suborder - Hystricomorpha ("porcupine like")
All except Coypu have (1) a
vaginal closure membrane and
(2) a masseter muscle
insertion that passes through
the large infraorbital
foramen. Other suborders
include Sciuromorpha:
"squirrel-like" ... such as
squirrels, marmots, gophers,
beavers, and Kangaroo rats and
the suborder Myomorpha: "ratlike" ... house mouse, norway
rat, hamsters, voles, gerbils,
etc.)
Family - Caviidae (tailless South
American rodents with (1) one
pair of mammae and (2) four
digits on front feet and three
digits on hindfeet.
Genus - Cavia
species - porcellus
C.
Varieties ("types" or "breeds") - Characterized by
length, texture, and direction of growth of hair)
1.
ENGLISH:
a.
Short, smooth, straight hair (3.8 cm)
b.
Solid colors: albino, white, black, agouti,
sandy, red, chocolate, cream, etc.
c.
Bicolored and tricolored animals also.
d.
Most inbred and outbred laboratory guinea
pigs are the English variety.
D.
2.
ABYSSINIAN:
a.
Short, course hair that radiates from
multiple centers on the body to form
rosettes.
b.
Variety of colors.
3.
PERUVIAN:
a.
Has long silky hair up to 15 cm (6 in) long.
b.
Absence of two hip rosettes are referred to
by fanciers as "angora" or "shelties".
Laboratory Stocks and Strains
1.
Listings of available stocks and strains are
provided in the ninth edition of the ILAR
publication "Animals for Research", and the "NIH
Rodents 1980 Catalogue"
2.
Outbred English stocks listed in above sources:
a.
Dunkin-Hartley--("albino")
b.
Hartley--("albino")
c.
Pirbright-Hartley
d.
Shorthair
3.
Inbred Strains:
a.
Strain 2 and 13 are the only two inbred
guinea pig strains used to any extent.
b.
Only remaining strains developed by Wright at
the U.S. Bureau of Animal Industry in 1915.
4.
Mutant Stocks/Strains:
a.
Complement 4 Deficient (C4D/N):
(1) Developed from spontaneous mutation in
NIH multipurpose guinea pig stock in
1970.
(2) Partially dominant mode of inheritance;
i.e., heterozygotes have intermediate
levels of C4 activity.
(3) Most immunologic reactions are normal.
b.
Waltzer (Wz)
(1) Wz mutation occurred spontaneously in
NIH guinea pig stock in 1953.
(2) "Waltzing" or circling and deafness
develop due to atrophy of organ of Corti
cells.
(3) Inherited as an autosomal dominant gene
with full penetrance.
(4) Homozygous condition results in high
perinatal mortality.
II.
c.
Hairless and Immunodeficient Mutant (LAS
29(6): 744-748, 1979):
(1) Spontaneous mutant strain from Hartley
stock at Eastman Kodak Company in 1979.
(2) At birth, are smaller, have tannish skin
with numerous wrinkles, and have stunted
vibrissae.
(3) Shortened lifespan; many die during
first week, one lived for 9 months.
Body hairs rare, short, and poorly
retained; a few have temporary fuzzy
hairs.
(4) No grossly visible thymic tissue, cystic
spaces found where thymus should have
been. Germinal follicles reduced or
absent in lymph nodes and intestinal
lymphoid tissues.
(5) Hypogammaglobulinemic.
(6) Deaths due to systemic cytomegalovirus
(intranuclear inclusion bodies in
cardiac fibers), systemic balantidiasis,
and Pneumocystis carinii.
d.
Hairless Euthymic Guinea Pigs:
(1) Now available from Charles River
Laboratories.
(2) Hair bulb, erector pili, and sebaceous
glands do exist.
(3) Produces defective hair shaft
(4) Reduced number of shafts
(5) Normal functional thymus
BIOLOGY
A.
Anatomy
1.
Skin and external features
a.
Hair and skin:
(1)
Consist of coarse large guard hairs
surrounded by undercoat of fine hair.
(2)
Each hair follicle has associated
sebaceous gland
(3)
Sudoriferous glands absent
(4)
5-6 rows of tactile hair (vibrissae) on
lateral nose
(5)
Prominent hairless area (1-1.5 cm diam)
just caudal to pinna of each ear.
(6)
b.
2.
Perineal Sac: Bilateral diverticula in
circumanal region containing large
accumulation of sebaceous glands. White
waxy accumulations termed "scrotal
plugs" in males.
Mammary Glands:
(1)
Both males and females have a single
pair of inguinal teats surrounded by a
hairless area.
(2)
A single large papillary duct opens to
exterior.
Dental Formula:
1 01 3
2(I-C-PM-M-) = 20 teeth.
1 01 3
a.
Diastemal space between incisors and
premolars.
b.
A11 teeth continue to grow for lifetime of
the animal.
3.
c.
The molars are hypsodontic = prism shaped
teeth with high crowns
d.
With medial inclinement of the teeth and
continuous growth, encasement of the tongue
may occur
e.
Only one set of teeth (monophydont)
Bones
a.
Vertebral formula:C7,T13-14,L6,S2-3,Co4-6
6 sternebrae. 13 or 14 pairs of ribs:
1st-6th sternal
7th-9th contribute to costal arch
10th-14th are floating
b.
Feet:
Forefeet have 4 digits each:
(3 phalanges in each digit except
4th which has 2)
Rear feet have 3 digits each.
c.
Vestigial clavicles present.
d.
Pelvic Girdle:
(1)
Consist of ilium, ischium, acetabulum,
and pelvis bones.
(2)
Pubic symphysis generally remains
fibrocartilage throughout life of
animal.
(3)
The pubic symphysis degenerates 2 weeks
prior to parturition resulting in
complete destruction by parturition
(4)
Palpation of separation can be used to
estimate parturition.
4.
5.
Muscular System
a.
Well developed masticatory muscles (Masseter
and digastricus)
b.
Reflects the gnawing behavior and
corresponding mastication by grinding (versus
chewing).
Cardiovascular/Respiratory System
a.
b.
c.
6.
Pharynx:
(1)
Soft palate is continuous with base of
the tongue and lateral walls of the oral
cavity
(2)
Opening into larynx is a small
intrapharyngeal ostium (AALAS Abstract
#96, 1983)
Lungs:
(1)
3 left lobes (cranial, middle, caudal)
and 4 right lobes (cranial, middle,
caudal, accessory)
(2)
Pleural cavities are continuous (LAS
16(5): 411, 1966)
Arteries: 3 deviations from normal mammalian
vascular pattern (Amer. J. Anat. 139, 269284. 1974):
(1)
There may be 2 or 3 pairs of renal
arteries (versus normal 1 pair in most
mammals).
(2)
The abdominal aorta gives rise to a
celiomesenteric trunk instead of
separate celiac and cranial mesenteric
arteries.
(3)
A bronchoesophageal artery passes from
the right subclavian, the right internal
thoracic, or the brachiocephalic trunk
instead of from the aorta.
Hemolymphatic System
a.
Thymus:
(1)
Present in immature animal
Gradually involutes as the animal
matures.
b.
7.
(2)
In adults may be completely gone or
persist in caudal cervical or cranial
mediastinum.
(3)
Thymic tissue is replaced primarily with
fat as age progresses.
(4)
In immature animals it is composed of 2
compressed lobulated glands on each side
of the ventral cervical midline.
(5)
Extends from the angle of the mandible
approximately halfway to the thoracic
inlet (Cooper and Schiller, 1975).
(6)
Accessory thymic lobes in most guinea
pigs; usually paired and adjacent to the
parathyroid gland or fused to it (Cooper
and Schiller, 1975).
(7)
Guinea Pig used extensively for
immunologic studies because the cervical
thymus is easily removed (LAS 25, 82-84,
1975).
Parathymic Lymph Nodes:
(1)
Located in cervical region.
(2)
Receive lymph from the thymus.
(3)
Studied to determine the immunologic
inter-relationship between the thymus
and lymph nodes.
Gastrointestinal System
a.
b.
Tongue:
(1)
Rostral one-third is free.
(2)
Remainder attached to floor of oral
cavity.
(3)
Small filiform papillae anteriorly,
large fungiform papillae posteriorly.
Stomach:
(1)
c.
No keratinized non-glandular portion
present i.e., all glandular.
Small Intestine:
(1)
About 125 cm (50 in) in length
(2)
d.
e.
Cecum:
(1)
Occupies left side of abdominal cavity
(2)
Large thin-walled sac 15-20 cm long.
(3)
Accounts for about 15% of body weight.
(4)
Has 3 taenia coli (dorsal, ventral and
medial)
(5)
Produces out-pouchings called haustra.
Peyers patches:
(1)
f.
h.
About nine flat white 1 mm diameter area
of lymphocyte aggregates on mucosal
surface.
Colon:
(1)
g.
Common bile duct enters duodenum 1 cm
caudal to pylorus.
Ascending, spiral ascending, transverse,
and descending portions.
Liver:
(1)
6 lobes: right and left lateral, right
and left medial, caudate and quadrate.
(2)
Cystic duct from gallbladder joins
common hepatic duct to form common bile
duct.
Pancreas:
(1)
Divided into cranial and caudal lobes.
(2)
Pancreatic duct enters duodenum 7 cm
distal to common bile duct.
i.
Salivary Glands: 4 pairs present
Parotid
Mandibular
Sublingual
Molar (Zygomatic).
j.
Microscopic Features of GI tract:
(1)
Pseudohemosiderosis: normal
accumulation of hemosiderin in the
lamina propria of the villa of small and
large intestines.
8.
Reproductive System
a.
Male:
(1)
Os penis present
(2)
Inguinal canal remains open throughout
lifetime
(3)
Vesicular glands (seminal vesicles):
large, coiled. tubular, long (10 cm)
(a) Intra-abdominal glands
(b) Contain a creamy thick white fluid
that forms concretion (vaginal
plug) when mixed with coagulating
gland secretions.
(4)
b.
9.
10.
Other accessory sex glands include:
(a) Coagulating gland:
i)
Duct opens into the calyculus
seminalis of the urethra
ii) A small white median papilla
which protrudes into the
urethral lumen.
(b) Bulbourethral glands
(c) Prostate
Female:
(1)
Ovaries:
(a) Corpora lutea produced each 16-17
day cycle
(b) Grossly visible as small pink
structures.
(2)
Vaginal closure membrane:
(a) Usually perforate only at estrus
mid-gestation, and parturition.
(3)
Cervix:
(a) Each horn of the uterus opens into
the cervix
(b) A single os cervix opens to the
vagina.
Urinary System:
a.
Kidney: Has a single longitudinal renal
papilla with lateral calyces.
b.
External urethral orifice in female opens
independently from the vagina onto the
perineum.
Adrenal Glands:
a.
Triangular in shape; bilobed; with lateral
lobe larger than medial.
b.
Larger in males than females
c.
Strain 2's have significantly larger adrenals
than outbred stocks (Am.J. Anatomy 63(2):273295, 1938)
B.
d.
Are the largest adrenals relative to body
weight among animal species; the larger size
is due to a thicker cortex
e.
Guinea pig and human secrete cortisol as
their main glucocorticoid hormone (vs.
corticosterone in most rodent species)
Physiology
1.
(Reference BGP 63-98)
Hemo-Lymphatic System
a.
b.
c.
White Blood Cells
(1)
Neutrophils
38%
(2)
Lymphocytes
55%
(3)
Monocytes
3%
(4)
Others
4%
Chemistries
(1)
Glucose
60 - 100 mg%
(2)
BUN
8 - 20
(3)
Plasma Protein
5.2 - 6.0
(4)
Serum Calcium
4.5 - 6.0
mg%
Erythrocytes:
(1)
RBC Numbers:
4.5-7.0 x 106/mm3.
(2)
PCV:
(3)
Mean Corpuscular Vol. (MCV):70.3-85.0
(4)
RBC Life Span:
(5)
RBC's are fairly fragile.
37-48%.
60-80 days
d.
e.
(6)
Hemoglobin: 11.0-15.2 gm/100 ml blood.
(a) Resistant to oxidation by nitrites
to methemoglobin (also rat, mouse,
hamster, and gerbil) versus species
very susceptible to nitrite
oxidation (man, monkey, dog, and
rabbit)
(b) Has high oxygen affinity because of
high levels of 2,3-DPG (as do rat,
rabbit, dog, horse, man, and guinea
pig) versus those species with low
oxygen affinity (cat and ruminants)
(7)
MCHC = 30.5%
(8)
Acute hemolytic anemia in response to
excess dietary cholesterol (versus
cardiovascular lesions in most animals).
Kurloff Cells:
(1)
Unique mononuclear leukocytes containing
round or ovoid cytoplasmic inclusions
called Kurloff bodies: from 1-8 microns
in diameter.
(2)
Inclusion is prob. a mucopolysaccharide
substance secreted by the cell itself.
(3)
Numbers increase markedly during:
(a) Pregnancy
(b) Exogenous estrogen treatment
(c) Increases are rare in fetus and
neonates.
(4)
0.24% of WBC's in males
(5)
Number in females varies with estrous
cycle.
(6)
High numbers found in placenta. They
may constitute a physiologic barrier
separating fetal antigens from
immunologically competent maternal cells
(7)
Originate from spleen and thymus
Lymphocytes: Lymphomyeloid complex (LMC)
studied because:
(1)
The neonatal guinea pig possesses a very
mature lymphocyte, similar to human
infants
(2)
The guinea pig more nearly resembles man
immunologically and hormonally than rats
and mice
(3)
f.
g.
2.
Thymus:
(1)
At one year, most thymic tissue is
involuted with fat deposits.
(2)
Thymectomy reduces lymphoid organ
weights and produces lymphopenia.
(3)
Guinea pig (also ferret, monkey and man)
is considered a corticosteroid-resistant
species because steroid treatment does
not readily affect lymphocyte count or
thymus. (Other species respond with
decreased thymus weights and lymphocyte
counts).
Bone Marrow:
that of man:
Guinea pig marrow similar to
(1)
Easily dispensed
(2)
Stains well
(3)
Actively erythropoietic at birth (unlike
rat).
Cardiovascular System
a.
3.
Cervical thymus is readily accessible
for thymectomy / modification.
Blood Distribution:
(1)
Plasma volume:
(2)
Blood volume:
3.88% of body weight
6.96% of body weight
b.
Heart Rate: resting (by telemetry) was 275
(229-319) per minute.
c.
Blood Pressure:
100 mm Hg.
d.
ECG:
systolic rarely greater than
similar to human.
Reproductive Physiology
a.
General:
(1)
Guinea pig a good animal model because:
(a)
It is easy to handle
(b)
Has distinct signs of estrus
(vaginal membrane opening)
(c)
Predictable reproductive behavior.
(2) Most closely resembles woman of all
small laboratory animals because:
(3)
b.
(a)
Has a long cycle (15-17 days)
(b)
Ovulates spontaneously
(c)
Has an actively secreting corpus
luteum.
In the laboratory, guinea pigs are
polyestrous, nonseasonal breeders.
Puberty:
(1)
Female: First estrus at 30-134 days
(mean 67.8+21.5 SD)
(2)
Male:
56-70 days
c.
d.
Estrous Cycle:
(1)
Length:
13-20 days average is 16 days.
(2)
Proestrus: (lasts 1-1.5 days)
(a) Signs include increased activity
and vigorous pursuit of cagemates
(b) Vigorous mounting in the ten hours
prior to estrus.
(3)
Vaginal membrane:
(a) Opening precedes estrus
(b) Open for about 2 days during cycle.
(c) Open for average 11 days during 1st
cycle; 5 days on future cycles
(d) Closure occurs after ovulation.
(4)
Estrus: (lasts 9-11 hours):
(a) Exhibit copulatory reflex (lordosis
or opisthotonos)
(b) Receptivity occurs during darkness.
5 p.m. to 5 a.m.
(5)
Ovulation: Occurs 10 hours after onset
of estrus and is spontaneous.
(6)
Postpartum estrus:
(a) Occurs with a 12-15 hours
postpartum
(b) Lasts approx. 3.5 hours.
(7)
Vaginal Smears:
(a) A better indicator of estrus than
vaginal opening.
(b) Onset of estrus indicated by
rounded cornified cells.
(c) Influx of leukocytes indicates
ovulation.
Hormonal Control of Ovarian Activity:
(1) Corpus luteum (CL):
(a) Secretes progesterone, which
increases rapidly after ovulation.
(b) Luteal cells hypertrophy between
days 3 and 9
(2)
FSH (follicle-stimulating hormone):
(a) Increases about day 13
(b) This promotes estrogen synthesis by
the developing follicle.
(3)
e.
f.
An LH (luteinizing hormone) surge
effects ovulation.
Fertilization and Implantation:
(1)
Fertilization occurs in fallopian tubes:
(a) Must occur within 20 hours of
ovulation.
(b) Usually only 3.4 ova (range 1-5)
ovulated.
(2)
Implantation:
(a) 8-12 cell stage enters uterus on
day 3
(b) Implants on day 6-7.
(3)
Postestrus insemination
(a) Within 0-16 hours
(b) Intraperitoneal AI of semen
reported to be as successful as
natural mating during estrus.
Gestation:
(59-72 days; mean = 63 days)
(1)
Length is inversely related to number of
fetuses carried.
(2)
Females may double weight due to fetal
mass
(3)
Hormonal Control of Pregnancy Involves:
(a) CL of pregnancy continues to grow
until day 18-20
(b) CL remains functional throughout
the pregnancy.
(c) Placenta begins endocrine
(Progesterone) activity after day
15
(d) Pregnancy can be completed
subsequent to bilateral ovariectomy
after day 21.
(e) Progesterone: plasma levels
increase rapidly after 15 day postcoitus; peak between days 30-45.
(f) Estrogens: Appear at day 20; peak
at day 56-60; undetectable
following parturition.
g.
Placentation:
(1)
h.
Discoidal, Labyrinthine Hemomonochorial
(a) Has a single layer fetal capillary
membranes that are in direct
contact with maternal bloodstream
(b) Very similar to humans.
ARM Hemochorial: also found in rat,
mouse, hamster, rabbit, &
armadillo).
Parturition:
(1)
Symphysis pubis begins to relax in
response to relaxin
(2)
Returns to normal within 24 hours
postpartum.
(3)
Parturition lasts 10-30 minutes with an
average interval between deliveries of
7.4 min (range = 1-16 minutes).
(4)
Average age of sow at first litter is
175 days (range 93-420).
(5)
Litter Size: Ranges from 1-8; Ave. is 3.
(6)
Neonate Viability, Size Growth:
(a)
(b)
(c)
(d)
(e)
(f)
(g)
i.
Optimal survival if litter size is
2-4.
Stillbirth incidence increases with
size of litter.
Lowest mortality with 69 day
gestation.
Asphyxia from fetal membranes a
frequent cause of death.
Fetalphagia not observed in the
guinea pig.
Stillbirth incidence reported as
high as 45% in some colonies;
especially Strain 13's.
Weight at birth inversely related
to litter size; average is 80 g,
60-130 g range.
Lactation:
(1)
Estrous cycle continues normally after
parturition regardless of whether sow is
or is not lactating.
(2)
Most offspring will survive if no
nursing, but weak, runty pigs may
result.
j.
C.
(3)
Peak lactation period is during days 58; agalactia by day 18-23, or 24 hours
after pups removed. (Weaning usually at
14 - 21 days).
(4)
Rate of pup growth directly related to
milk yield of sow.
Male Reproduction:
(1)
Puberty (presence of sperm in semen) at
around 10 weeks: sexual maturity (adult
concentrations of sperm) usually not
until 14-19 weeks.
(2)
Ejaculation occurs in the first or
second intromission; followed by a
refractory period of one hour before
copulation can reoccur.
(3)
Electroejaculation has been performed
with lumbar and rectal electrodes.
(4)
Liquification of coagulated semen can be
done with 0.1% chymotrypsin phosphate.
(5)
Vaginal plug is the portion of ejaculate
secreted by seminal vesicles which
coagulates instantaneously on emission
(characteristic of ORDER Rodentia).
Plug falls out of the vagina a few hours
after its formation.
(6)
Cobayin is a toxin found in the seminal
fluid of guinea pigs. Produces death in
0.5-2.0 hours when given IP to rabbits.
Behavior (Ref. BGP pp. 31-52)
1.
Behavior in the Wild
a.
b.
C. porcellus, C. aperea, C. cutleri:
(1)
Do not dig burrows, but use burrows
excavated by other animals, crevices in
rocks, or shrubbery.
(2)
The alpha male is intolerant of sexual
activity by lower ranking males.
(3)
Mutual grooming not excessive.
Diet:
c.
2.
(1)
Green grass and vegetables
(2)
Are especially fond of alfalfa
(3)
Do not store food
Activity:
(1)
Most active in morning and evening
(2)
Little evidence of parental defense of
young
(3)
Response to danger is either immobility,
or sudden explosive scattering of
animals.
Perception and Individual Behavior Patterns
a.
Perception
(1)
Vision: Eyes open at birth, but poorly
developed depth of vision and object
discrimination
(2)
Audition: Maximum sensitivity between
500 and 8000 Hz. Range: 125-40 or
50,000.
(3)
Gustation:
(4)
b.
c.
(a)
Avoid sweet foods, especially if
more than 0.5M glucose
(b)
Reject overly bitter, salty, or
chemically pure diets
Other: Olfaction (pheromones esp.)
probably important in behavior.
Activity Patterns:
(1)
Under constant illumination, almost
continual activity mostly feeding and
self-grooming.
(2)
Less activity with excessive heat (7585oF).
Responses to Dangers:
(1)
"Immobility response":
(2)
(3)
(a)
Tend to freeze in response to unfamiliar sudden sounds
(b)
A self-protection response; last a
few seconds, or up to 20 minutes
(c)
Electrical shock may also evoke
this immobility response; thus not
good subjects for pain or shock
avoidance studies.
"Scatter Response":
(a)
Usually elicited by sudden
movements
(b)
Involves stampeding in all
directions, jumping from a cage,
trampling young, or rapid circling.
Preyer reflex: Cocking of the pinna of
the ears in response to a short signal
from a Galton whistle (Clapped hands
will work)
d.
Feeding and Elimination Behavior:
(1)
Feeding:
(a)
(b)
(c)
(2)
Drinking:
(a)
(b)
(c)
(d)
(3)
With sipper tubes guinea pigs don't
lick, draw out water by grasping
tube and pulling head back.
With ball bearing antidrip devices
in tubes, gnawing occurs.
With a water dish the head is
tilted back after each sip.
Newborns can learn to drink from
sipper tube within 48 hours of
birth.
Elimination:
(a)
(b)
(c)
e.
Generally occurs during daylight
hours especially at dawn and dusk
Laboratory-reared animals feed both
at night and during the day.
Newborn animals can eat solid food
within the first day after birth.
Newborn guinea pigs usually
incapable of voluntary micturition
for several days postpartum (up to
1 week)
Maternal licking stimulates both
defecation and urination.
Coprophagy is commonly observed in
adults and weanling age young.
Usually eat fecal pellets directly
from the anus.
Social Behavior:
(1)
Tolerate close physical contact with
each other at rest
(2)
Seem to seek contact when moving about
(3)
Lactation: mothers assume a sitting
position to allow young to crowd under
the mother.
f.
g.
Grooming:
(1)
Little mutual grooming
(2)
Self-grooming observed as early as
birth; usually after feeding.
(3)
Hairpulling is common in pups pulling
hair from mother during or shortly after
end of lactation.
(4)
Hair pulling and ear-chewing can be
exaggerated under crowding and stress.
Communication
(1)
Olfactory:
(a)
(b)
(2)
Auditory:
(a)
(b)
(c)
(d)
h.
3.
Scent marking with anal glands is
common
Males mark with supracaudal gland
by rubbing rump.
"chutts" - brief vocalizations (.05
sec.); single or paired
"chutter" - 2 to 4 components
"whine" - during flight, discomfort
or evasion
Also have whistle, tweet, purr,
drr, scream, squeal.
Dominance Relations:
(1)
Conflict arises over space, access to
food, drink, objects to gnaw on.
(2)
Offensive responses:
(a) Range from vocal response to
chasing to deep bite wounds
(b) Male adults: when caged with
females may result in death of the
less dominant males
Reproductive Behavior:
a.
Mating Behavior:
(1)
Male Behavior: Anogenital investigation
by sniffing or licking, mounting with a
forepaw clasp, pelvic thrust, intromission and ejaculation.
(2)
Female Behavior:
(a)
(b)
b.
Female displays lordosis, wide
stance of hind feet, and perineal
dilation (opening of vaginal
closure membrane).
Estrous cycle:
i)
Behavioral estrus is 8 hours
ii) Best indicator of receptivity
is lordosis posture in
response to a male or gentle
stroking toward head over
rump
iii) Occurs nocturnally
Female Parental Behavior:
(1)
Parturition
(a)
(b)
(c)
(d)
(2)
First pup born after 5 minutes of
labor
Born head first; the mother then
licks and nibbles until fetal
membranes are consumed and pup is
cleaned.
Interval between pups usually less
than 3-4 minutes
Placenta usually expelled after
pups are born; most are eaten by
mother or others in pen.
Maternal Solicitude:
(a) Once the dam enters postpartum
estrus, shows little interest in
offspring till mating is completed.
(b) Maternal care is limited
i)
Passively allows nursing
ii) Neonatal grooming limited to
anogenital stimulation.
III. CARE AND MANAGEMENT OF GUINEA PIGS
A.
Environment
1.
2.
3.
Temperature
a.
Optimal temperature range is 65-75oF (1724oC). Slightly higher for the hairless GP
(75 - 79oF)
b.
Above 90oF may see:
(1)
Heat prostration and deaths especially
in advanced pregnancy
(2)
Abortions
(3)
Sterile matings from males
c.
Poor growth in young if below 55oF (13oC)
d.
Guinea pigs tolerate cold better than hot
temperatures
e.
Type of caging affects optimal room
temperature; i.e., higher temperature needed
for wire-bottom cages.
f.
Control of temperature fluctuations more
important that actual temperature as guinea
pigs are more sensitive to variations than
other laboratory species.
Relative Humidity:
a.
40-60% (50% optimal)
b.
Survival of airborne organisms is lowest at
this level.
Ventilation
a.
10-15 air changes per hour.
b.
Air velocity and direction of flow should be
designed to produce a draftless and even
distribution of air.
c.
Auxiliary power should be available for the
environmental control system.
4.
Space requirements for guinea pigs
a.
Animal Welfare Act
(1)
Minimum height:
(2)
Minimum floor space:
size
under 350 gm
over 350 gm
breeders
b.
space (square inches)
60
90
180
NIH ("Guide for the Care and Use of
Laboratory Animals, 1985)
(1)
Minimum height : 7 in (17.8cm)
(2)
Minimum floor space:
size
under 350 gm
over 350 gm
5.
6.5 inches
space (square inches)
60
101
Caging
a.
Usually constructed of stainless steel,
fiberglass, polycarbonate, or plastic.
b.
Usually in batteries on portable racks (some
breeders us fixed tiered compartments, but
regular disinfection difficult)
c.
Solid bottom, bin type cages are most common;
especially for breeding animals.
d.
Wire floors should be welded, rather than
interwoven mesh; recommended sizes vary from
1/2" to 1 1/2" square; (smaller size should
be avoided to preclude broken legs).
e.
Tumblebrook cage is commonly used for
breeding. It is a portable 5 cage rack: each
solid bottom cage is 30 x 30 x 10 inches.
6.
7.
B.
Bedding
a.
Peat moss, dried corn cobs, cedar shavings,
pine shavings, straw, hardwood chips
b.
Pine shavings are popular
c.
Any bedding should be free of dust
d.
Sawdust has been reported to cause
infertility in guinea pigs due to adherence
to genital mucosa (vulva or prepuce) and
interference with copulation.
e.
Cereal straw and wood chips may produce upper
G.I. (mouth, esophagus) injuries with
resultant infection and mortality.
Cage Sanitation
a.
High concentrations of mineral salts in
guinea pig urine result in accumulation of
mineral scale
b.
Weekly rotation of acid and alkaline
detergents has been effective in removing
this scale
c.
Should be sanitized, i.e., water heated to
180oF, live steam, or effective chemical
disinfectant
Feeding
1.
Vitamin C
a.
Guinea pigs and primates are the only
commonly used laboratory animals which
require an exogenous dietary source of
Vitamin C (ascorbic acid). Vitamin C is also
required by fruit-eating bats and some birds.
b.
Are unable to convert glucose to ascorbic
acid because they lack the microsomal enzyme
L-gulonolactone oxidase.
c.
Ascorbic acid required to:
(1)
Prevent scurvy
(2)
Maintain natural disease resistance
(3)
To maintain blood complement
(4)
d.
e.
f.
Essential coenzyme in the hydroxylase
reactions forming hydroxyproline and
hydroxylysine, which are components of
collagen.
Deficiency results in:
(1)
Formation of defective collagen
(2)
Enlarged costochondral junctions
(3)
Disturbed epiphyseal growth centers
(4)
Hemorrhages in various tissues
(5)
Delayed wound healing
(6)
Impaired bone and tooth formation.
Daily Ascorbic Acid requirements:
(1)
Immature guinea pigs:
weight
0.5 mg/100 g body
(2)
Maintenance (over 300 g BW):
(3)
Breeding females:
6 mg
20 mg
Sources of Vitamin C:
(1)
Commercial Guinea Pig feed:
(a) Feed within 4-6 weeks of
manufacture (although under
"proper" storage conditions,
adequate ascorbic acid levels
should be present for 90 days).
Commercial feeds usually contain
1000 mg/kg.
(b)
(c)
(2)
Supplementation with ascorbic acid in
drinking water:
(a)
(b)
(c)
(d)
(3)
(b)
(c)
(d)
3.
Should be added only to distilled
or deionized water since
chlorinated tap water will
inactivate ascorbic acid.
Add at the rate of 200-400 mg/L
Undergoes rapid oxidation and
requires frequent preparation (or
use of automatic dispenser)
Copper and other metals should not
be used in the watering system as
they catalyze ascorbic acid.
Stainless steel is satisfactory.
Green Vegetable Supplementation:
(a)
2.
Should store at 50oF or less for
best preservation of ascorbic acid.
Ascorbic acid deteriorates rapidly;
accentuated by heat.
Kale:
i)
115 mg ascorbic acid per 100g
ii) Should be washed in a
hyperchlorinated solution to
minimize bacterial
contamination.
Carrots, cabbage, sprouted grains,
chicory, marigolds have also been
used.
Lettuce is a poor source of Vit C.
10-44% average increase in weaned
offspring with the use of green
vegetable supplements has been
reported.
Feeders:
a.
Standard "J" type feeders or wall-mounted
feeders with a baffle work well in keeping
guinea pigs from climbing into the feeders.
b.
Bowls are not desirable because guinea pigs
tend to sit, sleep and defecate in the bowls.
Feed Consumption:
a.
Growing guinea pigs eat about 8% of their
body weight in feed daily. Adults eat about
6% body weight daily
b.
Pelleted diets preferred (label and date
secondary feed containers to avoid confusing
with rabbit chow)
c.
4.
5.
6.
C.
Alteration in composition of a feed or
introduction of a new feed may result in a
sharp decline in feed consumption to the
point of starvation or signs of vitamin
deficiency occur.
Protein:
a.
Have an usually high requirement for certain
amino acids (arginine, methionine, and
tryptophan)
b.
Requirements can be met by providing 18-20%
protein diet usually of plant origin.
Roughage:
a.
Crude fiber should be 13.5% (ILAR, 1967)
b.
Many breeders advocate feeding hay; may
reduce boredom and decrease "barbering"
c.
Has been reported to decrease hair thinning
often associated with late pregnancy.
Experimental Diets:
a.
Guinea pigs discriminate between feeds within
a few days of birth. Dietary preparations
for nutritional studies should therefore be
introduced within a few days of birth.
b.
Acceptance can be enhanced by pelleting
powdered diets in gelatin, moistening feed,
or transitory mixing.
Water
1.
2.
Requirements (Adults):
a.
With "greens" supplement - 50-100 ml per day
b.
Without "greens" supplement - 250-1000 ml per
day (excess amount required because of
spillage).
Spillage:
D.
a.
Occurs because guinea pigs play with sipper
tubes and rapidly empty water bottles
b.
Can be controlled by:
(1)
Fitting drinking bottles with ballbearing equipped sipper tubes.
(2)
Mounting automatic watering systems
slightly (3/4") outside the cage (must
adjust valve pressure to prevent water
from squirting into the cage).
3.
Water bowls not recommended because guinea pigs
rapidly foul the water with excreta.
4.
Guinea pigs will blow food and other materials
from their mouth up through the sipper tubes.
5.
Sipper tubes should be made from stainless steel
or other hard material since guinea pigs chew
rather than lick the end of the tube
Breeding
1.
2.
Males:
a.
Fertile matings before 8-10 weeks of age
b.
Usually mated at 3-5 months (450-600 gm)
c.
Many breeders mate at weaning. Efficient
reproduction until 27-30 months of age.
Females:
a.
First estrus as early as 4-5 weeks of age
b.
Usually mated between 2.5-3 months of age, or
when reach 450-600 gm.
c.
Should be bred by 6 months of age to lessen
likelihood of the animal:
(1) Becoming excessively fat
(2) Having firm fusion of the symphysis
pubis, both of which may result in
contributing to dystocias or pregnancy
toxemia.
E.
d.
Efficient reproduction until 27-30 months of
age.
e.
Females should have produced five or more
litters.
Breeding systems:
1.
Monogamous pairs:
a.
One male and one female are mated in a single
cage.
b.
Most commonly used to maintain pedigreed
nucleus or foundation colonies of inbred
strains which require brother x sister
matings.
\A
Intensive:
d.
2.
(1)
Male remains with female throughout
parturition and breeds during the
postpartum estrus which occurs 3-4 hours
after parturition
(2)
Results in an average of 5 litters per
year per sow.
Non-intensive:
(1)
Female separated from the male just
prior to parturition.
(2)
Female bred during the first regular
estrus following postpartum estrus.
(3)
Results in 3.5 litters per year per sow.
Polygamous Mating (Harem Breeding)
a.
Used for outbred production
b.
One boar mated with 4-6 sows.
maintained as:
(1)
Can be
Intensive groups:
(a)
The group is maintained as a stable
colony and held intact throughout
their useful breeding life
(b)
Maximizes advantage of postpartum
breeding and communal rearing of
young
(2)
Non-intensive groups:
(a)
Sows in advanced pregnancy are
isolated either individually or in
groups for farrowing
(b)
After weaning the sows are returned
to the mating pens.
3.
Reproductive Index:
female per month.
a.
b.
4.
5.
The number of weanlings per
Outbreds:
(1)
Average litter size 3-4
(2)
Reproductive index is 1.0 for most
commercial breeders
Inbreds:
(1)
Average litter size 2-3
(2)
Reproductive index is 0.7 weanlings per
month per female.
(3)
Lower index is attributed to a decline
in vigor and fertility displayed by a
reduced frequency of farrowing and
smaller litters.
Breeding Colony Mortality:
a.
Abortions in one report of 8.3%
b.
Stillbirth incidence increases with larger
litters. Stillbirths are frequent in
primiparous animals.
c.
Other causes include embryonic resorptions,
uterine hemorrhage, pregnancy toxemia,
dystocias, and exhaustion from prolonged
labor are common causes of death in breeding
colonies.
Birth Weights and Growth:
a.
Depend on nutrition, genetics, a litter size,
gestation length, and litter interval.
b.
Average weight in litter of 3-4 is 85-95 gm
c.
Young weighing less than 50 g usually die
F.
d.
Should weigh 165-240 g at 21 days
e.
Weaning usually between 15-21 days, or 180 g
weight
f.
Gain 2.5-3.5 g per day during first 2 months
g.
Weight gains slow but continue to 12-15
months of age
(1)
Adult sows
700-850 gms
(2)
Adult boars 950-1200 gms
Handling
1.
The guinea pig is easily excited
2.
Vocalize frequently when excited
3.
Should be approached and handled in a gentle quiet
manner.
4.
Are docile, easily handled and seldom bite.
5.
Guinea pigs are very susceptible to stressful
situations.
a.
Transportation and handling may result in
significant weight losses (up to 50g) within
24-48 hours.
b.
This weight is regained rapidly if conditions
are stabilized but may alter experimental
data.
6.
Abortions are not uncommon in late pregnancy
following movement or frightening events.
7.
Restraint:
a.
Should be grasped firmly and quickly around
the thorax from above with one hand.
b.
The thumb should be behind a front leg and
fingers forward of the opposite limb.
c.
As the animal is lifted, the free hand should
be placed under the hindquarters to support
and control the caudal portion of the body;
especially late pregnancy females.
G.
H.
Sexing
1.
In young guinea pigs, females exhibit a "Y"-shaped
fold in the genital area. The female also has an
external urethral orifice separate from and
ventral to the vagina.
2.
Young males have a slit in the anogenital area.
The penis is easily extruded from the prepuce with
gently pressure and is located just anterior to
the "slit".
EM
Note: the anogenital distance is the same for
females and males.
Identification:
1.
Multicolored animals may be identified by their
natural markings.
2.
Ear tags: Not too satisfactory because they are
easily torn from the ear or fall out due to earchewing by cagemates. Used successfully by some
breeders.
3.
Ear notching: Notches may heal closed or the ears
become shredded from fighting, obliterating the
notches.
4.
Ear tatoos: Use a cutting edge suture needle or
special pliers. Use black ink on white and green
ink on pigmented ears.
5.
Fur Dyes:
a.
Used temporarily for up to 6 weeks
b.
Clean fur with 70% alcohol to remove fur
grease and allow to dry
c.
Use any of the following solutions, made up
in 70% alcohol:
(1)
Saturated picric acid (yellow)
(2)
3-5% acidic, basic, or carbol-fuchsin
(red)
(3)
3-5% methyl or gentian violet (purple)
(4)
3-5% brilliant, ethyl, or malachite
green
(5)
I.
3-5% trypan blue
Drug Administration
1.
2.
3.
Intramuscular injections:
a.
Give in the posterior lateral thigh 0.5 to 1
cm above the stifle.
b.
In large guinea pigs, the lumbar musculature,
although caution should be exercised.
Intraperitoneal injections:
a.
Inject slightly to the right of the midline
about one inch anterior to the pubis at a low
(30o) angle.
b.
Elevate rear of animal to shift viscera
anteriorly.
Subcutaneous injections:
a.
Easily made in dorsal location (nape of
neck).
b.
The flank mat also be used, but caution
should be exercised.
4.
5.
6.
Intravenous injections:
a.
Use 23-27 gauge needle.
b.
Facilitated by sedation (e.g., Ketamine HC1)
various routes used, including:
(1)
Caudal auricular vein (LAS, Feb 1981, pp
85-86)
(2)
Cephalic vein
(3)
Femoral vein
(4)
Lateral metatarsal vein - largest
superficial vein
(5)
Dorsolateral penile veins
(6)
Lingual vein
Chronically implanted catheters:
a.
carotid artery
b.
jugular vein
Oral Route:
a.
b.
One report suggest this is easily
accomplished by using:
(1)
Bulbed needles
(2)
5 french infant feeding tubes
This may damage the mouth (due to small
intrapharyngeal ostium), so use a small
syringe and feed the medication per os
J.
Blood Sampling
1.
2.
3.
4.
5.
Anterior vena cava (Lab Animal, 11(6): 66-68,
1982)
a.
Lightly anesthetize guinea pig
b.
Use 23 gauge, 1 inch needle inserted at notch
between manubrium and first left rib
c.
Yields several cc's blood rapidly
Femoral Triangle (artery and vein) (LAS, 25(2),
1975, pp 216-217)
a.
Use 23 ga, 3/4 inch needle
b.
Yield 3 cc or more blood
Cardiac Puncture:
a.
Requires light anesthesia
b.
Insert needle at the intercostal space and
apical beat, or lay animal on back and insert
at 30o angle in the xiphoid area.
c.
Should be used as a terminal procedure only.
Vacuum assisted bleeding (LAS, 25(1), 1975, pp
106-107)
a.
Nick the superficial surface of the lateral
metatarsal vein distal to malleolus. Coat
the leg with silicone grease petroleum jelly.
b.
Use - 0.5mm Hg vacuum over leg.
c.
Yields 3 cc blood per minute.
Orbital Sinus puncture
a.
Microhematocrit capillary tubes introduced
into medical canthus of the eye.
b.
Should be lightly anesthetized.
K.
6.
Toenail clipping - small volumes
7.
Ear Veins:
(LAS, 33(1), 1983, pp. 70-71)
a.
Punctured with a mechanically-activated
lancet: blood collected in capillary tubes
b.
Allows frequent, multiple small volume
samples to be collected
Anesthesia of Guinea Pigs
1.
General considerations
a.
b.
Fasting for 12 hours prior to anesthesia
recommended to:
(1)
Prevent regurgitation of stomach
contents
(2)
So that the weight measured just prior
to anesthesia is more apt to represent a
true value.
Stage 3 surgical anesthesia plane
characterized by:
(1)
Flaccid skeletal muscles
(2)
Disappearance of reflex responses
(3)
Shallow, regular respiration.
c.
During stage 3, may exhibit peculiar
squirming movements in one leg or entire body
which cease spontaneously (additional
anesthetic at this point may be fatal).
d.
Atropine sulfate may be used as a
preanesthetic to decrease salivation.
2.
Inhalation Anesthetics:
a.
b.
c.
Methoxyflurane (Metofane)
(1)
Excellent anesthetic for guinea pigs
(2)
1% for induction, 0.3% for maintenance
(3)
Induction takes 15-18 minutes; recovery
10 or more minutes.
Halothane, Isoflurane
(1)
Considered "high risk" because guinea
pigs first hold their breath and then
breathe deeply
(2)
Halothane: reported to be hepatotoxic
in guinea pigs following repeated
dosages. Causes a 35-40% decrease in
blood pressure.
Administration of Inhalation Agents:
(1)
Anesthesia chamber
(2)
Nose cone
(3)
Bell jar
(4)
Endotracheal intubation:
(5)
3.
EMA
Use a canine otoscope to visualize
larynx
(b)
A 5 french urinary catheter can be
used as a tracheal tube (JAVMA
179(11), 1981, p 1295).
Tidal volume of 3.8 ml/kg body weight.
Injectable Anesthetics:
a.
Sodium Pentobarbital:
(1)
Dose: 28-35 mg/kg I.P. gives 30-100
minutes of surgical anesthesia.
(2)
Should be diluted 50% in normal saline.
b.
Thiopental (Pentothal):
(1)
Dose:
20-55 mg/kg IP; 20 mg/kg IV
(2)
Dilute to 1% concentration
c.
Thiamylal Sodium (Surital):
d.
Ketamine Hydrochloride:
e.
f.
20 mg/kg IP
(1)
Dose: 22-44 mg/kg IM gives excellent
sedation for venipuncture, tattooing,
etc.
(2)
Combine with 5-10 mg/kg xylazine IM to
produce light anesthesia
(3)
Surgical anesthesia with 44 mg/kg
Ketamine plus 5 mg/kg xylazine IM
(Abstract No. 88, LAS
32(4), 1982, p. 434)
(4)
Self-mutilation has been associated with
IM Ketamine in guinea pigs, (LAS, 34(5),
1984, p. 516); (IP injection should be
considered)
Fentanyl-Droperidol (Innovar-Vet):
(1)
Dose:
0.22 ml to 0.88 ml/kg IM
(2)
High dose may produce nerve, vessel, and
muscle necrosis and self-mutilation of
digits at 7-10 days post-injection.
(3)
Causes vasodilation which may aid in
venipuncture at peripheral vessels.
Telazol:
(1) Dose: 10 - 140 mg/lb plus 8 mg\kg IM
mixed
(2)
Provides good anesthesia for most
procedures
(3)
Gives about an hour of working time
L.
Antibiotic Therapy
1.
Many antibiotics apparently cause an alteration in
the intestinal flora which leads to diarrhea or
death within 3-5 days. Clostridium difficile
toxin has been suggested as the cause (LAS 31(2):
156-160, 1981)(Med Micro & Imm 169:187-196, 1981)
P5
"Toxic" antibiotics include:
3.
M.
a.
Penicillin
b.
Bacitracin
c.
Erythromycin
d.
Clindamycin
e.
Lincomycin
f.
Chlortetracycline
g.
Oxytetracycline
h.
Streptomycin
"Safe" antibiotics include: (from Williams,
C.S.F., 1976):
a.
Chloramphenicol palmitate:
daily for 5-7 days
60 mg orally
b.
Chloramphenicol succinate:
IM
10-30 mg/kg BID
c.
Sulfamethazine: 4 ml of 12.5% solution/500
ml of drinking water for 1-2 weeks
d.
Cephaloridine: 10 mg/animal/day
Euthanasia
1.
Carbon dioxide in a closed container
2.
Barbiturate overdose IP
3.
T-61 Euthanasia Solution
IV.
GUINEA PIG GENETICS
A.
Background:
1.
B.
1900-1960's genetic research was concerned with:
a.
The genetic analysis of coat colors
b.
The texture
c.
Studies on the effects of inbreeding.
2.
Genetic research today is directed at the analysis
of biochemical, physiological and immunologic
characteristics.
3.
Many mutants that have been described are no
longer obtainable.
4.
Diploid chromosome number is 2N=64, with one pair
of sex chromosomes and 31 pairs of autosomes.
5.
Sex determination is xx (female) and xy (male).
Pigmentation:
1.
15 loci are known to influence coat color in
guinea pigs. Most are known to have a single gene
mode of inheritance.
2.
Individual loci:
a.
Agouti locus (A):
(1) This locus controls amount and
distribution of:
(2)
:\W
Eumelanin (black or brown pigment)
(b)
Phaeomelanin (yellow and reddish
pigment) both in individual hairs
and in the coat. Two alleles
recognized.
Light-bellied agouti allele (A): Agouti
with light belly. This is the wild type
for Cavia porcellus with terminal or
subterminal yellow band (phaeomelanin)
and rest of the hair black or brown
(eumelanin).
(3)
b.
c.
Non-agouti allele (a): Eliminates the
phaeomelanin band from individual hairs
and animals are therefore black (or
brown, or variation).
Brown locus (B):
(1)
Wild type allele (B):
(eumelanin)
Black color
(2)
Brown allele (b): changes eumelanin in
hair, skin, and eyes brown black to
brown. When combined with agouti wild
type, a cinnamon-agouti color results.
Color, or albino locus (C):
(1)
A series of mutants at this locus
reduces the amount of pigment. There is
no true albino allele homologous to that
in mice(c).
(2)
Wild type allele (C): full
pigmentation. Examples include blacks,
reds, golden agoutis. All of these have
black eyes.
(3) Acromelanic albino (ca):
(eumelanin reduced to patches on
extremities (nose, feet, ears). Yellow
(Phaeomelanin) eliminated completely.
Eyes are pink due to lack of pigment in
the iris and retina.
(4)
C.
Black
The ca allele interacts with the
extension allele (e) at the E locus to
give a synthetic albino (ca/ca e/e) color
in the common laboratory DunkinHartley"albino" guinea pig.
Pelage Variations:
1.
Rough (R) locus: the dominant gene R is necessary
for any "roughness" rosette patterns.
a.
"Roughness" or rosettes: this hair pattern
is characteristic of the Abyssinian breed and
is regulated by four loci.
b.
2.
V.
The action of this gene is modified by the
incompletely dominant genes M and Re.
Long Hair (l):
a.
Autosomal recessive character
b.
Hair length up to 8, 12. or 16 cm at 3, 5,
and 7 months
c.
Peruvian breed: has long hair (1/1) and
rough (R) alleles, resulting in 2 hip
rosettes which throw hair forward over head.
d.
Smooth coated long haired type referred to as
"angoras" or "shelties"
"GERM FREE AND SPECIFIC PATHOGEN FREE" GUINEA PIGS (BGP, pp.
21-30)
A.
Background
1.
2.
3.
Germ-free Guinea Pigs
a.
Not commercially available
b.
Impractical to maintain breeding colonies
because enlarged cecum contributes to poor
breeding performance.
c.
Usually obtained by hysterotomy /
hysterectomy of conventional animals.
d.
Germ-free neonates are marked by precocious
behavior requiring little or no handfeeding
(sterile milk unnecessary), easily reared to
maturity.
e.
First germ-free pigs derived by cesarean
section in 1895 (Nuttall and Thierfelder).
Gnotobiotic Guinea Pigs
a.
Preferred term for disease-free guinea pigs.
b.
Obtained by germ-free derivation and then fed
a defined bacterial flora.
Germ-free Husbandry-- Often individually housed
to:
B.
a.
Avoid tendency to nurse at the anal end of
cagemates
b.
To avoid hair pulling and chewing
Germ-Free vs. Conventional
51
Cecal distension
a.
Conventional animals' cecum is 15% of body
weight, 30% in germ-free.
b.
Same weights as conventional when corrected
for increased cecal size.
c.
Attributed to lack of resistance to
stretching in the cecal wall.
d.
Predisposes to cecal rupture, herniation,
torsion, volvulus, and uterine prolapse.
e.
Anal and rectal prolapse has increased
incidence of about 5%.
2.
Kurloff bodies not observed in germ-free guinea
pigs--reason unknown (observed however with
induced protozoal infections).
3.
Hypoplastic GI lymph nodes and lymphatics
4.
WBC:
5.
6.
a.
Total WBC: 1900 in germ-free vs. 5 -12,000
in conventional
b.
Neutrophils:
conventional
55% compared to 10-20% in
c.
Lymphocytes:
42% vs. 80% in conventional
Immunoglobulins:
a.
Gamma globulins same until 8-10 weeks of age,
then decrease in germfree to 20-50% of
normal.
b.
Hemolytic complement activity same.
Pregnancy
a.
Frequent in germ-free, but rarely reach term
b.
Sows abort; prolapse uterus, often death
c.
Cecal distention postulated as cause of
reproductive problems
7.
Germ-free are slower to develop signs of scurvy.
8.
Miscellaneous Abnormalities
a.
Enlarged gall bladder
b.
Decreased muscle tone
c.
Thin gut wall
d.
Reduced lymphoid tissue
VI.
SELECTED BIBLIOGRAPHY:
GUINEA PIGS
1. Altman, P.L. and Katz, D.D (eds.), "Inbred and
Genetically Defined Strains of Laboratory Animals, Part 2:
Hamster, Guinea Pig, Rabbit, and Chicken", Federation of American
Societies for Experimental Biology, Bethesda, MD, 1979.
2. Clark, J.D. and Baker, H.J., The Guinea Pig: I.
Introduction and Husbandry (V-6085); II. Biology (V-6086), and
III. Diseases (V-6087) (2x2 slide/ cassette tape programs), ACLAM
and Washington State University.
3. Cooper, G. and Schiller, A.L., "Anatomy of the Guinea
Pig", Harvard University Press, Cambridge, 1975.
4. Festing, M.F.W., The Guinea Pig In "The UFAW Handbook on
the Care and Management of Laboratory Animals", 5th ed., edited
by UFAW, Churchill Livingstone, NY, 229-247 (1976)
5. Holmes, D.D., "Clinical Laboratory Animal Medicine":
Iowa State University Press, Ames, IA, 1984.
6. Manning, P.J., Wagner, J.E., and Harkness, J.E., Biology
and Diseases of Guinea Pigs, In "Laboratory Animal Medicine",
Fox, J.G., Cohen, B.J., and Loew, F.M., eds, pp. 149-181 Academic
Press, 1984.
7. National Academy of Sciences, National Research Council,
Institute of Laboratory Animal Resources, "Guide for the Care and
Use of Laboratory Animals", National Academy of Sciences,
Washington, D.C., 1985.
8. Obeck, D.K., The Guinea Pig, In: Aeromedical Review 474, Selected Topics in Laboratory Animal Medicine, Volume 22,
USAF School of Aerospace Medicine, Brooks Air Force Base, TX,
1974.
9. Wagner, J.E. and Harkness, J.E., "The Biology and
Medicine of Rabbits and Rodents", 2nd ed. Lea and Febiger,
Philadelphia, 1983.
10. Wagner, J.E. and Manning, P.J. (eds), "The Biology of
the Guinea Pig", Academic Press, NY (1976).
11. Williams, C.S.F., "Practical Guide to Laboratory
Animals", C.V. Mosby Co., Saint Louis, MO, 1976.
12. Stokes, W. S., USARIID Seminar Series, 1986.
13. Rothman, S. W., "Presence of Clostridial difficile
toxin in guinea pigs with penicillian-associated colitis. Med J
Immun, 169(1981)187-196
14. Charles Rivers Update, "Euthymic Hairless Guinea Pigs
for Dermatological Studies". Vol 1, Number 2, Spring 1986
15.
Mallort V. T., "Comparative Delayed Contact
Hypersensitivity in Haired versus Hairless Guinea Pigs".
Pharmakon Research International, Waverly, Pa. July 1987
16. Flecknbell P. A., "Laboratory Animal Anesthesia".
Harcourt Brace Jovanovich, New York, NY. 1987