1. Guinea Pig Cavia porcellus
Biology and Anatomy

2. Origin Cavia porcellus – domesticated Cavia aperia – wild
Wild – Peru, Argentina, Brazil, Uruguay
Also known as Cavies
Domesticated 16th century – England

3. Uses of Guinea Pigs
Pets
Scientific research
Food

4. The guinea pig (Cavia porcellus or cavy), is a docile rodent used in the United States as a pet and as a research animal

5. 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.

6. “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.

7. “Taste like chicken”
“Have some Pisco in hand”

8. 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.

9. Hydrochoerus hydrochaerus
Uncle Skeeter
Erethizon dorsatum
Cousin “Booger”
Hydrochoerus hydrochaerus
Aunt Charlene
Chinchilla laniger
Cousin “Bubba”
Octodon degu

10. Varieties of Guinea Pigs
Traditional
American or English – short hair
Abyssinian – whorls of short rough hair
Peruvian – long hair

11. 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

12. Traditional varieties of guinea pigs

13. The most common pet varieties are the English Shorthair and the American Shorthair.

14. The Abyssinian has short rough hair arranged in whorls or rosettes.

15. The Peruvian, or 'rag mop' variety, has long silky hair
The Peruvian, or 'rag mop' variety, has long silky hair. Guinea pigs of each variety may be mono-colored, bicolored, or tricolored

16. New varieties of guinea pigs

17. Silky – soft, medium hair

18. Teddy – short, coarse hair

19. American crested – contrasting whorl on head

20. Rex – very short, soft hair

21. Hairless – (well, almost)

22. 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.

23. Basic Guinea Pig compact stocky body tailless diurnal – actually
short naps night and day
sebaceous marking glands - rump
open rooted teeth

24. Additional characteristics
vocalize – at least 11 sounds
good swimmers
seldom jump
rarely bite or scratch
need frequent handling
lifespan – 4- 5 years
Group housed guinea pigs establish male-dominated hierarchies. This is often expressed by circling and vocalizations.

25. 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.

26. 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.

27. 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

28. ANATOMY AND PHYSIOLOGY

30. 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

31. 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

32. Digits
Guinea pigs have four digits on the forelimbs and three digits on their hindlimbs.

33. 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.

34. TEATS
Both the male and female have teats. The female has a single pair of inguinal mammary glands.

35. 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.

36. 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.

37. 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.

38. 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.

39. Which one is the male?

40. 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.

41. 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.

42. 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.

43. 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 per minute
The heart rate is beats per minute.
Adult body weight for the sow is grams and, for the boar, grams.
Page 154

44. Physiologic values cont..
Puberty days
Breeding age 3-4 months
Gestation period days
Litter seize 2-5 pups
Weaning age days

45. 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.

46. REPRODUCTION Sow and Boar
The sow is a nonseasonal, continuously polyestrous breeder, with an estrous cycle of days. The sow also exhibits a fertile estrus approximately hours postpartum.
Usually the sow is bred at two-three months of age, which corresponds with a body weight of 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 ( grams body weight)

47. 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.

48. 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.

49. When are you due?

50. Within 24 hrs!
Hey doc, can’t you at
least wear a glove?

51. 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

52. Care of Young precocial – born two nipples – inguinal region
furred, eyes open, teeth erupted
walking within 2 hours
two nipples – inguinal region
can care for four young
litters 3-4 (range 1-6)

53. 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

54. 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