I often notice people stating that you should never breed Roan to Roan, because you will get malfunctioning babies or dead babies or whatever. Well, this is not all there is to say about this!
Generally it is the Dalmation (as in this photo) that you should never breed to a Dalmation. A Dalmation is based on a dominant gene (Wh - dappled), which as the homozygote (WhWh) will give a microphthalmic baby (white baby with very small pink eyes). The whwh is the normal coloured cavy. The dapple/Dalmation gene in itself produce grouping of white hairs among the normal coloured hairs. This means that a Black Dalmation (aaWhwh) have black hairs with groups of white hairs, which often looks like the cavy is almost spotted. They also have ruby eyes.
Before the Dalmation gene were known among scientists it was called Rs,
as a provisional name. Later it was given its real name, Wh.
Since you will get half Black Dalmations aaWhwh and half
Self Black aawhwh
if you mate Self Black to Black Dalmation, there is
no need to mate Dalmation to Dalmation and get these
microphthalmic babies.
This applies to all possible colours, just breed Dalmations
of the right colour to selfs of the right colour!
To breed good Dalmations: Breed a Dalmation to a Self with a
Dalmation parent. This will get the most predictable results.
Never breed Dalmations to Dalmations! If you do breed
Dalmations to Dalmations you can be sure that one fourth of
the babies will be microphthalmic whites...
If you want to read more about Dalmations - get a copy of "Colour Genetics of the Cavy" by Catherine Whiteway. And also "Colour Inheritance In Small Livestock" by Roy Robinson, the well known geneticist. In Whiteway's book the gene is still called RS, in Mr Robinson's book it has already been named Wh.
With the Roan (sisi), there is another gene (dm, diminished) that, if it exists in the stock, might give sickly white babies with a few spots of colour, in combination with Roan (dmdmsisi). But the breeders who do not have this dm gene in their stock do not have to worry. They will never produce any white sick babies even if they only breed Roan to Roan!
I didn't have a roan photo so I made a little drawing of a roan :-)
The Roan gene produces interspaced white hairs in the fur,
not grouped but single.
SiSi is the normal coloured cavy. Sisi is said to carry si.
Sisi may show a small amount of roaning, since the si is
not totally recessive to Si. The show variety Roans are sisi.
With Roan it is said that on some genetic backgrounds the lighter
coloured animals may carry dm, so do not breed light coloured
specimens of the colour you are breeding.
Roans don not have ruby eyes liked Dalmations,
instead a Black Roan has black eyes.
Some breeders use the Wh - Dalmation gene to produce "mock roans", these are actually called Dapples, and are just Dalmations that look like Roans. This is especially true in the US where it seems like the true Roan gene is lost, so a US Roan is genetically Dapple (Which means that it is really a Dalmation...). So: NEVER breed a US Roan to a US Roan!
To be able to distinguish between true Roan and Dapple you need to be able to distinguish between dominant and recessive traits. The Roan is recessive (sisi) and the Dapple/Dalmation is dominant (Rsrs). This means that a breeder that claims to breed dominant roan actually are not breeding Roan at all, but Dapple (Rsrs), that really are nothing else than Dalmations (Rsrs). To confuse the issue further the si gene is not completely recessive, which means that the heterozygote Sisi is mainly unsilvered, but some Sisi animals might have a lot of silvering. Thus people might not understand that it is a recessive gene they are dealing with.
The difference between the US Roan and the Dalmation is purely polygenic. Therefore it is very important in the US not to mix these varieties in breeding or you might end up with inbetween varieties that are Rsrs but neither good Dalmations nor good Dapples.
If you want to read more about Roans - get a copy of "Colour Genetics of the Cavy" by Catherine Whiteway. And also "Colour Inheritance In Small Livestock" by Roy Robinson, the well known geneticist. In Whiteway's book the gene is still called RS, in Mr Robinson's book it has already been named Wh.
Copyright Eva Johansson.
Last update: 11th of February 2006.