Les gris classiques: mythe ou réalité
...et comment les reproduire
La traduction française est en cours et sera disponible sous peu...
What defines a classic grey?
Classic grey is specific pattern caused by a genetic mutation (an variant allele) in the KIT gene that creates a dilution of the solid base coat colour. Classic silver grey and classic rosegrey phenotypes both stem from the same KIT mutation. An animal exhibiting this pattern only requires one copy of the variant allele to express it on a phenotypic level. This pattern often creates white, fully diluted areas on the animal's extensions (face, neck and legs) but it can also be expressed to different degrees. Some classic greys will have full white face that can extend down their neckline, with white sometimes on their feet or even up to their knees. Other carriers of this pattern will have atypical presentation with smaller white facial areas and no other white areas. Although there are new theories that would possibly explain the variations between the degree of expression of classic grey, this variation is still not well understood on a genetic standpoint at this time. However, colour genotyping now provides a great way to identify carriers of the classic mutation, whether they are fully expressed, minimally expressed, or cryptically expressed.
See examples below...
Most classic greys will display at least 2 separate colours (sometimes up to 3 or 4!) in their fiber which is typically their base coat colour and a lighter shade of that base colour (dilution effect). This variation in colour can be expressed between primary and secondary fibers or can even be expressed within the secondary fibers (1 typically darker colour for primary fiber and 2 lighter colour tones found in secondaries). This variation between fiber colour does affect uniformity of colour (obviously!) but also can affect uniformity of micron (SD) as the lighter shades tend to be finer than the darker shades. On a genetic/fiber production standpoint, these are probably the most challenging aspects in breeding classic greys. They also present as interesting aspects to improve thanks to well planned out breeding strategies.
Is breeding classic grey to classic grey lethal?
Well, yes and no! This question keeps coming up and although there is some truth to it, it might not be as gloomy as it seems. Classic greys each carry one genetic copy of the classic grey mutation and one unmutated copy. The unmutated gene copy is coded for the production of a solid-coloured, non-classic pattern. They can only pass on one of those copies to the embryo (either classic or solid).
With that in mind, breeding classic grey to classic grey can create a lethal combination but only if embryo inherits the classic grey mutation copy from both parents. The fact that both parents can randomly pass on only one of those two copies to their offspring creates 4 different outcomes (see below). The homozygous lethal combination can only happen 25% of the time. If the embryo receives the double dose of classic grey, it will simply fail genetically speaking and gestation will terminate very quickly after fertilization of the follicle (10 -14 days). The dam will simply be open and receptive at her next follicular cycle. If you eliminate the lethal outcome (meaning that the breeding holds and you have a confirmed gestation), classic grey to classic grey mating will yield 2/3 classic greys and 1/3 solid offspring.
How often is the classic gene transmitted to progeny?
For a classic grey to solid-coloured alpaca breeding: ratio is 1/2 (50%)
For a classic grey to classic grey: ratio is 2/3 (66.6%)
What does a “cryptic” classic grey alpaca mean?
Cryptic: Something concealed, hidden, mysterious, puzzling or ambiguous.
The word “cryptic” is not scientific by any means but it is often used to describe a classic grey that would be phenotypically expressing the classic pattern in a very faint or minimal way. Cryptic phenotypes in classic grey are often seen in fully diluted animals (alpacas carrying the “ee” genotype) but can also be seen in darker phenotypes. On darker phenotypes, an animal only displaying a small white spot or a very faint expression can easily be mistaken for another pattern such as white spotting. Now that colour genotyping provides confirmation for the classic grey gene, it is easier to rule out the white spotting gene on cryptic or atypical presentations of classic grey.
Can the classic gene skip a generation?
If logic is followed, it cannot skip a generation. Based on what we know at this time, the classic gene can only be transmitted to progeny by an alpaca carrying the actual mutation regardless of its level of phenotypic expression (fully expressed, atypical or cryptic). Fully diluted, cryptically expressed classic greys do carry the classic gene and will pass it onto progeny with the same frequency as a fully expressed classic. On the other hand, a solid-coloured alpaca genotyped as “Non-Grey”, even if it was produced by 1 or 2 classic grey parents, would not have received the mutation at all and therefore would not be able to pass on the classic gene to progeny as it simply does not carry the mutation in its DNA.
That said, it is not completely impossible that a solid-coloured alpaca produced by 1 or 2 classic grey parents and who has inherited 2 “non-grey” copies, be able to pass on a solid copy to their own progeny that could hypothetically be more prone to "magically" mutate into classic grey. From experience, I have never seen this happen! Although this hypothesis is up for debate, it still remains scientifically unproven to this day.
Is classic grey related to the white spotting gene?
These two dilution patterns stem from closely related DNA mutations and are located in the same DNA area (KIT gene). Although they are somewhat similar, they do not have the same effect on phenotypic expression of colour. As previously mentioned above, classic grey is a dilution pattern that has the potential to affect the entire base coat colour as opposed to the white spot pattern, that creates distinct white spot(s) or area(s) on an animal without typically affecting or diluting the base coat colour in its entirety. White spotting typically creates more isolated white areas and although we can find them on extremities like classic greys (face and legs), they can also be more randomly distributed across the body. So essentially, classic grey and white spotting are closely related mutations in the KIT gene area but they act very differently on the phenotypic expression of colour.
Can classic grey to classic grey breeding yield a BEW (Blue Eyed White)?
BEW: Blue Eyed White
Total absence of colour pigmentation that creates white coated animals with blue eyes.
A high percentage of those animals are also deaf at birth.
BEW can only occur with two scenarios and none of them involve classic grey to classic grey breeding. As seen above, classic grey and white spot mutations are closely related and these are the ones you want to avoid breeding together.
Scenario #1: Classic Grey bred to White Spot
A classic grey animal bred to a white spot carrier (genotype tested as “Non-Grey”) will yield 25% BEW. White spot pattern is an incomplete dominant just like classic grey, meaning that the alpaca only requires one copy to express the pattern. With that in mind, both animals in this scenario also carry an unmutated copy for a solid pattern. This basically means that with this breeding, you can produce 25% BEW, 25% Classic Greys, 25% White Spot and 25% Solid-coloured animals.
BEW produced this way would have inherited both type of mutations; a copy of the classic grey mutation from its classic grey parent and a copy of the white spot mutation from the other. Offspring produced with this type of breeding, even when expressing coat colour, seem to often carry some degree of blue in their eyes (specks, partial or full blue eyes).
Scenario #2: White Spot bred to White Spot
Breeding two white spot carriers (genotype tested as “Non-Grey” animals) will yield 25% BEW, 50% white spot and 25% solid. White spot to white spot is not homozygous lethal (as seen in classic greys) and that is unfortunately the combination that will yield BEW.
Now that we have broken down how BEW are produced, we can easily assume that there are two types of BEW. Some are produced by breeding classics greys to white spots and others are produced by breeding two white spots together. Although they are all categorized as BEW, these animals do not carry the same exact pattern mutations.
With the rise in popularity we have seen in classic greys in the last couple of years, it safe to assume that more and more BEW will be inadvertently produced. Questions will soon follow on to how to breed these subjects or if they should be bred at all. There has always been somewhat of a stigma around BEW and an ethical debate around if they should be bred or not. I personally think that this is up to each breeder to determine if the benefits outweigh the risks.
Let's break it down a little further and see how both type of BEWs would hypothetically breed. This will help determine the level of risk in potentially producing more BEW offspring and will also explains why some breeders have produced classics greys with BEW subjects.
CLASSIC GREY TO BEW
Scenario #1: Classic Grey to BEW carrying one classic mutation
We would have a 25% homozygous lethal combination as seen in classic to classic breedings.
The other viable outcomes are 33.3% BEW, 33.3% Classic Grey and 33.3% White Spot.
Scenario #2: Classic Grey to BEW carrying two white spot mutations
This breeding would yield 50% chance of BEW and 50% chance of White Spot. This is the scenario with the highest chance of producing BEW offspring.
SOLID (NON-GREY) TO BEW
Scenario #1: Solid (Non-Grey) to BEW carrying one classic mutation
In this one, there is no homozygous lethal and all outcomes are viable. This breeding would yield 50% Classic Greys and 50% White Spots. This might be the safest scenario! Although you can produce more white spot offspring, you can also produce classic greys and BEW chances would be null.
Scenario #2: Solid (Non-Grey) to BEW carrying two white spot mutations
This breeding would produce 100% white spot offspring. Although this is not a great scenario, it is the best and safest way to try to start breeding out the white spot gene out of this BEW dam without producing more BEW. Breeding those offspring to solid animals would give a 50/50 ratio of solid to white spot. Completely breeding out the white spot gene from this dam would take a minimum of 2 generations with a 50% ratio of those grand-offspring being completely solid and carrying no white spot mutation.
One last consideration for BEW...
Classic grey OR White spot bred to animals with lighter phenotypes
Breeding a classic grey OR a white spotting animal to a fully diluted "ee" animal (White/Beige/LF) should also be carefully considered beforehand as animals with lighter coat colour can also carry the white spotting gene and go unnoticed. It would simply be harder to visually identify white spot areas on a fully diluted animal. Unless you are absolutely certain that this animal does not carry the white spotting gene, this is the type of breeding that does carry a certain level of risk in potentially producing BEW. Just something to keep in mind…
FINAL THOUGHTS ON BEW
As mentioned earlier, with the heighten popularity of classic greys, we might actually see a rise in BEW outcomes in years to come. Although no breeder aims at producing BEW, it can happen and it is truly up to each breeder to determine if the benefits outweigh the risks in breeding them further. Thanks to the different scenarios outlined above, it's safe to assume that if you do decide to breed a BEW subject, the safest way to avoid producing more BEW is to pair them with solid-coloured animals and avoid breeding them to classic greys or white spotted animals.
Can classic greys be bred to modern grey (roan)?
Absolutely! Although much less is known at this time on how the modern grey pattern behaves genetically, there is no clear evidence that BEW can be produced by breeding classic greys to modern greys. Even though the modern grey pattern could potentially be found in the KIT gene (same DNA area where classic and white spotting can be found), this dilution pattern has not yet been clearly identified and therefore, cannot be reported with genotyping at this time. Some scientific studies are currently being conducted on modern greys and once the genetic marker is found, it will certainly be added in colour genotyping reports. What we do know from experience, is that the modern pattern does not seem to behave the same way as classic grey and white spotting so it is commonly known that there should be no risk in producing BEW with this type of pairing.
why do some classic greys have blue specks or crescent in their eyes?
This question keeps coming up! As seen earlier, classic grey is a dilution pattern that affect coat colour but it also seems to sometime affect eye pigmentation as well. Although we do not fully understand why some classic greys have normal eye colour while others have different degree of blue expressed, it is certainly linked to dilution factors. Classic greys and solid offspring that express some degree of blue in their eyes mostly seem to come from pairing two animals with dilution patterns. Classic grey, white spotting, modern/roan or other potentially unidentified dilution patterns (fading fawn?), when associated together, can potentially yield offspring expressing some degree of blue. This does not affect quality, breeding potential and overall health of these animals (no deafness as seen in BEW).
How to distinguish a classic silver from a classic rosegrey upon birth?
This question also keeps coming up! Although some classics are clearly silver at birth, a great percentage of them are also born with discoloured tips resembling rosegrey. There is a way of telling them apart even before growth of fiber reveals the actual colour of classic crias. From experience, the colour of the fiber on the ears (and sometimes even the tail or base of legs) on classic newborns is typically what gives it away! A classic silver cria will sport black base ear colour ranging from light silver to dark silver or even true black. A classic rosegrey cria will have red based ear colour ranging from light rose to dark rose or even solid fawn to dark brown.
Black Base Ears
Silver Grey Coat
Red Base Ears
COLOUR GENOTYPING AND CLASSIC GREYS
If you are interested in recent findings and observations relating to the expression and distribution of genotypes among classic grey population, I would invite you to follow the link below. The document starts with a general overview of genotyping followed by a large section dedicated to classic greys. It highlights how genotypes apply to classic grey, how ASIP can potentially influence the degree of phenotypic expression of classic and how to apply those concepts in a breeding program.
All the best in breeding amazing classic greys!
Alpagas Sutton Inc.