GUINEA PIG BIOLOGY

• Scientific name: Cavia porcellus
• Origin: South America
• Related to chinchilla and porcupine
• Naturally grazing animals; hay should always be available
• Most active in the morning and early evening; prefer to sleep during the day
• Three main breeds: English/common (short straight hair); Abyssinian (rough wiry hair in whorls; Peruvian (long straight silky hair)
• Crosses of all breeds sold as pets; purebreds of 11 different breeds used for shows

• Average weight (grams): male 900-1200, female 700-900
• Age at puberty (days): male 90-120, female 60-90
• Lifespan (years): 4-8, average 5
• Body Temperature: 99.0-103.1
• Heart rate: 230-380
• Respiratory rate (breaths per minute): 40-100
• Dental formula: I 1/1 C 0/0 P 1/1 M 3/3, all teeth open-rooted
• Sex determination: males have large scrotums and their penises can be easily extruded; females are usually smaller than males
• Sexually mature by 1 to 2 months old
• Estrus (heat) cycle length (days): 15-17; estrus phase of estrus cycle 6 to 11 hours long; ovulation is spontaneous; non-seasonally polyestrus
• Gestation (days): 59-72
• Litter size: usually 2 to 5, ranges from 1 to 13 pups
• Birth weight (g): 60-100
• Age eyes open (days): birth
• Weaning age (days): 14-28
• Breeding life: 3-4 years
• Separate adults before birth: no
• Food consumption per 100g body weight per day (g): 6
• Water consumption per 100g body weight per day (ml): 10
• Zoonotic diseases (diseases transmittable to people): allergies to dander and urine; bacterial infections (rare), including Bordatella, Salmonella, Yersinia, and Streptococcus; dermatophytes (ringworm); sarcoptic mites (mange)

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SPECIAL  CONSIDERATIONS

• Any painful condition can cause decreased appetite, and serious secondary illness can occur as quickly as 24 to 48 hours after the GP stops eating.
• Typically do not eat for 12 to 24 hours after giving birth.
• Lack the digestive enzyme l-gluconolactone and thus cannot synthesize vitamin C like other animals can, so they require a dietary source.
• Hindgut fermenters and coprophagic (eat their own feces); the droppings they eat are called cecotrophs and they are taken directly from the anus; this occurs several times a day
• Digestion of fiber occurs in the cecum and ascending colon; these portions make up ~65% of the gut
• Normal digestive tract bacteria are gram positive cocci, anaerobes and lactobacilli
• The menace reflex is a useful test in most animals for determining the ability to blink and see, but it cannot be used in GPs because they will not blink
• GP eyes have a limited tear film, small third eyelid, and few blood vessels in the retina
• Female GPS older than 1 year normally have multiple cysts on their ovaries; the cysts get larger and more numerous as the GP gets older
• Two glandular areas produce marking scents: the special skin along the midline of the lower back, and the fold around the anus (circumanal fold); both areas are more developed in males; GPs deposit scent from the circumanal fold by dragging their bottoms over a surface; males scent mark when their environment changes, when they conflict with another male, and during courtship; in addition to glandular secretions, urine and bacteria are responsible for components of the scents used in marking
• Obligate nasal breathers, so upper respiratory disease (nasal congestion without pneumonia) can cause severe difficulty breathing
• Urinary stones in GPS are usually made up of calcium carbonate or calcium phosphate, and thus show up on an x-ray
• In female GPs the opening to the urethra is not located in the vagina, but in a small bump in front of the vagina called the urethral papilla
• Male GPs have a tiny pouch, the intromittent sac, located next to the urethral opening within the glans penis

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