The American LaMancha is a breed whose standard doe not restrict it to one coat color. Anything goes, which fascinates and charms many breeders.
While we know relatively little about the precise mode of color/ pattern inheritance in goats, barnyard observations, in lieu of reliable genetic data, are adequate for most inquisitive breeders. What I am presenting here falls somewhere between the two. Fairly easy-to-read dog and cat studies - some available on the web - are useful in studying goats with only a few major exceptions.
The most convincing account of color inheritance in goats is provided by Dr.Phillip Sponenberg in "Breeding for Colored Angora Goats" which includes extensive material on "regular" goats (as he calls them.)
Thanks to the phenomenon of mutation many genes have evolved variants which are called "alleles"(contraction of allelomorphs meaning "other forms of.") Genes are strung on chromosomes ("capacity to take up dye") which travel in pairs, one inherited from the sire and one from the dam (think of the double helix.) Because the chromosomes have identical "addresses" (loci) for each gene form, only two alleles can be present in one individual. They can be the same (homozygotic), or different (heterozygotic.)
In the homozygous state genes can be either dominant or recessive in their expression. In the heterozygous state they are mixed dominant and recessive. Obviously, identical gene pairs are easier for the breeder to work with because they are expressed in the appearance (phenotype) of the carrier for better or for worse. Identical dominant genes present little mystery. Even though dominants may express imperfectly or incompletely, they do materialize in the phenotype, as we noted, whereas the recessive gene may be lurking for several generations without any indication of its presence. A recessive gene is not necessarily negative in spite of its murky reputation.
Since several genes have the potential to influence coat color there are different loci for the many variations. An alphabetical series keeps them in some sort of order for discussion. Problems arise as one tries to sort out the interactions of the genes. For example some genes can mask the action of other genes (epistasic - "placed above.") The genes being masked are referred to as hypostasic ("standing under.")
The color we see is produced by two types of pigment granules: pheo-melanin (red-yellow) and eu-melanin (black-brown.) The characteristic nature of the pigment as well as the greater or lesser amount (density or dilution) of the deposit determines the outcome. Variations can exist from hair to hair as in roaning. Also along the hair shaft (banding.)
The "A" locus is named after the agouti, a South American rodent whose hairs contain light and dark bands. Agouti is also used to signify the original camouflage color of many wild, later domesticated animals, showing ticked or banded hairs. The chamoisée, either wild or domesticated, is the model in goats. The typical chamoisée goat is tan. These hairs are either banded or roaned with stripes on the face and legs.
The most dominant allele on the "A" locus is not, however, the chamoisée, who is second in order of dominance. A non-stripe white/cream or tan color is the most dominant. It can, in effect, mask all of the patterns to follow on this locus. This should not come as any surprize to a LaMancha breeder.
Sponenberger postulates that all of the striped patterns, commonly referred to as "swiss markings," can be assigned to variations on the "A" locus.
Here are the colors/ patterns in order of dominance
as assigned by Sponenberger with my simplifications:
Black & Tan LaMancha
The B series introduces the recessive gene (b) which produces the grey-brown color associated with Toggenburg breed. The Togg, like the Oberhasli, can carry a gene for self (solid) black, although it is rarely expressed since both breeds have been subjected to many generations of pressure to eliminate the nonconforming gene. Dominant B causes dark pigmentation at any location to be black.
Togg marked LaMancha
D can either refer to "dense" in the dominant state, or "dilute" in the recessive state. The dilute modifiers (dd) are black to blue/grey and red to tan/cream.
The "E" locus controls the extension of the eumelanin pigment granules down the entire length of the hair shaft. In the dominant state (E) black masks the striping on the agouti locus. In the recessive state (ee) a true red speciman can be produced when the individual is also carrying the most domiant A gene. If she were an a t then the stripes would be dark red. If either of the above carried the d gene, the red would express as cream or tan.
White can be thought of as the absence of color. It is a mutation associated with domestication, and is usually considered dominant when expressed in the Saanen and Angora breeds. White can be inherited in other modes: both the "dilution" and "spotting" loci, provide a pathway when combined with other genes. Most "white" LaManchas are really light cream (A) and often carry color genes recessively thus not breeding true for white as the other two breeds consistently do.
The S locus is made of the white "spotting" genes which express independently of the black/red genes. Anklets, stars, tips, flags, blazes, and just plain spots, pop out seemingly at random and are all indicated by recessive "s," another marker of domestication. Great variabilty as to location and size is common. The "Dutch belt" pattern (a white ring encircling -more or less - the belly) is probably dominant. Ticking and reverse ticking (roaning) may, or may not, operate on a separate locus. The same applies to frosting, usually limited to ears and muzzle and possibly the throat.
Belted &Ticked LaMancha
Two categories which are difficult to fold into this classification series are the red-tinged black (sable?) and the red roan, which appear to be the most common LaMancha colors, reflecting their Spanish heritage. These two varieties cover the gamut from almost true black to mahogany and from almost true red to a roan indistinguishable from cream. Roaning is considered to be colored hairs intermixed with white hairs and may have its own locus. Sable is thought by some to reflect incomplete penetrance of black.
It is difficult to imagine that in the future the LaMancha breed will become a one color breed, but individual breeders may attempt to achieve more consistency of type within their herds by concentrating on one color or pattern.
Genes which control a variety of non-color traits (body type, size, production, component percentages etc) could possibly link up with genes for color when situated close to one another since genes on the same chromosome tend to stay together and be transmitted as a unit. Knowledge (intuitive or otherwise) of linked genes can lead to breeding greater overall uniformity. (Links can also be broken of course, and new combinations produced.)
The breeder's low-tech application of the "marker" theory, in effect, linking an observable color to other more elusive traits is more likely to be observable in a closely-bred family of LaManchas than across the breed as a whole.
Two easily recognized ancient breeds: The Greyhound dog and the Arabian horse are not limited by their standards (or nature) to a single color. However, breeders of these two venerable animals have always been highly mindful of the type which they are nurturing, without which the result would be common, plain, and lacking in any consistency regardless of color.
LaMancha breeders can take comfort in remembering the colorful history of the Greyhound and Arabian as they attempt to consolidate certain unique and desirable traits associated with their breed. Without having to give in to " one color fits all," some may find that one color may fit their family of LaManchas very well.
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