INTEGUMENT
Guinea pigs are born fully haired. The hair consists of large, coarse guard hairs with a fine undercoat. A prominent hairless area, measuring about 2.5 to 4 cm in diameter lies just caudal to the pinna on both sides.
This area lacks sebaceous and sweat glands and is more darkly pigmented than the remaining skin. It is larger in albino guinea pigs.Coat color
Guinea pigs can be one uniform color or mixed. The original natural color, agouti, is a combination of black and brown on each hair, but many colors are now possible. Albinos have red eyes with pink ears and feet. Himalayans have albino features at birth but develop dark points at the nose, ears, and feet. Brindle guinea pigs have a mixture of brown and black hairs.
Coat variety
The Self variety has smooth, short hairs lying in parallel segments. The Abyssinian has short hairs arranged in whorls that make its coat look uneven. When the periphery of these whorls meet in the midline it gives a crested or mohican appearance. Hair length for the Self and Abyssinian is around 35 mm but the Peruvian can grow hair as long as 200 mm, and the latter are mainly used as show animals (Cooper & Schiller 1975a).
Vibrissae
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These are long hairs used as tactile organs and there are seven groups divided according to their location. The buccal vibrissae lie in six parallel rows above the upper lip and are directed backwards from the muzzle. Two mental vibrissae lie on the chin while two nasal ones are located dorsolaterally on each side of the nose. Four supraorbital ones lie just rostral and dorsal to each upper eyelid and three infraorbital ones lie inferior and rostral to each lower eyelid (Cooper & Schiller 1975a).
Sebaceous glands
These are numerous along the dorsum and around the anus. The perineal glands are used for scent marking and contain a lot of sebaceous material. There are no anal glands. The caudal sebaceous gland sited at the coccyx lies 1 cm dorsal to the anus and is seen as an oval region that secretes pheromones and which becomes matted with sticky hair in adult males (Breazile & Brown 1976).
KEY POINTS
• Incisors and molars are open rooted, hence dental disease is common.
• Vitamin C is essential and scurvy can develop within
4 days of decreased intake.
• Males have a prominent caudal sebaceous gland and very large seminal vesicles.
• Females have a bicornate uterus, vaginal membrane, and separate urethral and vaginal orifices.
• The left and right mammary glands have separate blood supplies.
• The pubic symphysis dilates for parturition. Females should be bred before 7-10 months to prevent fusion and subsequent dystocia.