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THE LETHAL GENE - The white ones that are deliberately bred to die.





Microphthalmia better known as the 'lethal gene' in guinea pig breeding is cruel occurance thjat can happen in the breeding of guinea pigs and yet it is also completely avoidable.

It is estimated that approximately 25% of guinea pigs born from the breeding of two roan guinea pigs or two dalmation guinea pigs or two dalmation or roan carriers (guinea pigs with this breed in their background), will result in a lethal baby. A lethal guinea pig is always completely white with bluish pink eyes. It is worth noting that their are normal healthy  pink eyed white guinea pigs that are NOT lethals. These guinea pigs are not born from roan or dalmation parents or with disabilities. A lethal baby is born only from roan or dalmation parenting and lethal babies have obvious deformities.



What is a roan guinea pig?

A roan guinea pig has white hairs mixed with flecks of another solid colour through the white hairs. Some roan guinea pigs may only have a couple of roaned hairs which may not be easily noticeable. Below are photos of some roan guinea pigs.

What is a Dalmation guinea pig?

A Dalmation guinea pig looks very similar to that of a Dalmation dog. The dalmation guinea pig is of two colours being white with one other solid colour. The dalmation guinea pig can come in several colours including chocolate, lilac or black. The guinea pig will have the same single solid colour on all four feet, ears and face with a white blaze running up the face. The guinea pig will also have the same colour 'spots' down the body and then white through the rest of the body.

Above: A lethal baby born from a roan surrendered sow with no eyes and no teeth at ACS Brisbane Shelter in 2009. Sadly the baby only survived 48hrs.

Pictured below: What a 'roan' guinea pig looks like. White hairs mixed/flecked with another colour throughout all or parts of the coat.


ACS Shelters have had many roan guinea pigs surrendered each year. Many 'backyard' breeders do not know what a roan or dalmation guinea pig is and as a result it is uncertain exactly how many lethal babies are commonly born in Australia each year. ACS Shelters have had several lethal babies born due to the ignorance of those that have surrendered pregnant roan or dalmation guinea pigs to us. As a result we have encountered dead lethal babies and babies with deformities which have lived only to serve a life of disability. Several of the ACS Shelters have been forced to keep the lethal guinea pigs born that live due to their ongoing care requirements needed in order for them to survive and live a happy as close to normal life as they can.

Note: Click on thumbnails below to enlarge photos.





This terrible gene does not seem an issue to many. These breeds of guinea pig are also deliberately bred in the pedigree world of guinea pigs for their breed type and in turn to conform to a set standard. To achieve this standard of perfection for the show table naturally litters need to be bred each year.

Because the gene has been so inbred into many guinea pigs throughout Australia it is not uncommon at all to see a roan guinea pig. The roan gene is quite dominant in guinea pigs and roan offspring in turn is guaranteed.

Lethal guinea pigs a born with one or more of the following deformities and symptoms.

  • Born dead or dies within a few weeks of birth

  • Always born white

  • Born blind in one or both eyes

  • Born with no eyes

  • Born deaf in one or both ears

  • Born with unpigmented eyes

  • Mild to severe teeth deformities/missing teeth.

  • Low immune system

  • Permanent internal damage

Of those that survive, they will live their life with mild deformities. Most die young although their have been reports of some living for several years.

ACS is does not support the breeding of roan or dalmation guinea pigs.

Life should be valued and every life born is a gift and such little regard is common when it comes to the breeding of the roan gene. Many roan guinea pigs each year are deliberately bred whereby the guinea pigs owner knows full well that the roan gene will be bred on again and that in turn a lethal baby has a chance of being born with deformities, suffering and poor quality of life.

Their is no greater cruelty than intentional cruelty. Sadly though many lethal babies intentionally born, if they survive, are discarded by those that know what they are.

Those that do breed that are unaware of this gene may not even realise that they have bred a lethal white guinea pig.  In turn the babies may be seen as a stillborn or those that do survive may end up being further bred or sold. ACS Lakes Shelter had a lethal guinea pig surrender brought into the shelter  which had been found 'for sale' in a local petshop.

(c) Copyright 2006, Australian Cavy Sanctuary. All rights reserved.