Guinea Pig Cavia porcellus

Biology and Anatomy

Origin

Cavia porcellus – domesticatedCavia aperia – wildWild – Peru, Argentina, Brazil, UruguayAlso known as CaviesDomesticated 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 cleaned1/2 c. flour1/4 - 1/2 t. ground cumin salt and black pepper

to taste1/2 c. oilPat dry the skin of the guinea pig and rub inthe cumin, salt, and pepper. Preheat oil. Dustthe carcass with the flour and place it on itsback in the oil, turning to cook both sides.Alternately, the guinea pig can be cut and

friedin quarters.Serve with boiled potato or boiled maniocroot, and a salad of cut tomatoes and sliveredonion 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 SkeeterErethizon dorsatum

Cousin “Booger”Hydrochoerus hydrochaerus

Aunt CharleneChinchilla laniger

Cousin “Bubba”Octodon degu

Varieties of Guinea Pigs

TraditionalAmerican or English – short hairAbyssinian – whorls of short rough hairPeruvian – long hair

Varieties of Guinea Pigs

New varietiesSilky – medium length soft hairTeddy – short, coarse hairAmerican Crested – short hair with

contrasting whorl on foreheadRex – very short, soft hairHairless

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 mono-colored, 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-outbredIn 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 – actuallyshort naps night and day

sebaceous marking glands - rump

open rooted teeth

Additional characteristics

vocalize – at least 11 soundshttp://www.guineapigs-online.com/html/piggiesounds.html

good swimmersseldom jumprarely bite or scratchneed frequent handlinglifespan – 4- 5 yearsGroup housed guinea pigs establish male-dominated 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 humansGuinea 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 extra-abdominal 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 minuteThe 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 L-gulonolactone 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 15-17 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 atleast wear a glove?

NewbornsA 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 – bornfurred, eyes open, teeth

eruptedwalking within 2 hours

two nipples – inguinal regioncan care for four younglitters 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 ResearchV-9023L. J. Tambrallo, DVM, MSR. E. Fish, DVM, PhDOffice of Laboratory Animal MedicineUniversity of MissouriColumbia, Missouri