Roan (color) - Roan Guinea Pigs

Roan Guinea Pigs

The roan coloration of Guinea pigs is linked to microphthalmia. The allele that controls roaning in guinea pigs is incompletely dominant: an animal with one copy of the allele will have varying amounts of white hair scattered through its coat, particularly on the back and sides. This is not to be confused with the 'Magpie' variety, which is a brindled guinea pig lacking red pigment due to the "chinchilla" allele also responsible for self white and silver agouti coloration.

About 25% of guinea pigs born to a mating of two roans are completely white, with a constellation of deformities called lethal white syndrome, although it has no relation to Overo Lethal White Syndrome in horses or double merle syndrome in dogs. These symptoms include:

• Partial or complete blindness
• Partial or complete deafness
• Microphthalmia or anophthalmia
• Unpigmented eyes
• Missing or deformed incisors
• Deformed molars
• Elongated tooth roots
• Malabsorption in the small intestine, due in some cases to lack of intestinal villi
• Increased susceptibility to illness

It is worth noting that, unlike anophthalmic hamsters, lethal white guinea pigs are not sterile. Females may be unable to deliver live young.

Lethal white guinea pigs have a decreased lifespan in general, although individuals have reportedly lived to 6 or 7 years. Many die shortly after birth or at weaning age. With hand-feeding and regular dental care, lethals can live 2–3 years.