Breeding colored Angora goats is
challenging because breeders need to consider color, fiber character, and
conformation all at the same time. To further complicate matters, color
inheritance in Angoras is different than in other goat breeds. This
probably stems from the unique geographic origin of the Angora goat.
Color genetics is complicated and will take study before it makes
sense. Understanding color inheritance in "regular" (non-Angora) goats is
essential for appreciating color inheritance of Angoras, although Angoras
provide a few key exceptions to genetics of goat color in other breeds.
Appreciating the inheritance of color in Angoras will suggest some very
useful strategies for the production of top notch colored mohair.
Topics covered in this article include the following:
Color genetics is complicated and will take study before it makes sense. Understanding color inheritance in "regular" (non-Angora) goats is essential for appreciating color inheritance of Angoras, although Angoras provide a few key exceptions to genetics of goat color in other breeds. Appreciating the inheritance of color in Angoras will suggest some very useful strategies for the production of top notch colored mohair.
Topics covered in this article include the following:
A goat's final color results from the interaction of several independent processes, which makes control of color complicated. Interaction of the independent processes results in a wide array of colors. A general rule is that each final color is produced by a single combination of interacting components, although a few colors are exceptions. The interactions can be understood if the basic factors are taken one at a time. The final colors can then be appreciated as various combinations of the factors working together.
Genes are responsible for the machinery of life. In goats, as in all mammals, genes occur on chromosomes. Chromosomes can be thought of as strings of genes. Chromosomes occur in pairs and an individual gets one (of the pair) from the sire and the other (of the pair) from the dam. When a goat reproduces it contributes a random half of its chromosomes (one of each pair) to its offspring. The other half of the offspring's genetic makeup comes from the mate. Each gene takes up a specific site on a specific chromosome. This site is called a locus (plural loci), and frequently the genes are described by the locus name. Locus simply means an address for the gene: a specific place it occupies. Each member of a pair of chromosomes has identical loci, which accounts for the genes occurring in pairs.
When a gene occurs in more than one form the different forms are called alleles. The alleles of a gene all occur at the same locus, although each chromosome is limited to having only one allele at each locus. Each goat has at most a total of two different alleles per locus, since it has only two of each chromosome. Goat color varies because individual goats differ from one another in the specific allelic combinations they have at the various loci controlling the components of color.
The specific genetic makeup of a goat is called its genotype. The external appearance is called the phenotype, and may or may not completely reveal the underlying genotype. The condition of having two identical alleles at a locus is called "homozygous". When the alleles are different, the situation is called "heterozygous".
Alleles at a genetic locus interact in a variety of ways. Some alleles are not expressed unless both doses of the gene in an individual are the same (homozygous). These are recessive alleles (or genes, the terms are often used interchangeably). Dominant alleles, in contrast, are expressed identically whether in one dose (heterozygous) or two doses (homozygous). The dominant allele masks the expression of a recessive allele when the two are paired together. Recessive alleles are expressed as surprises when they are paired up following the mating of two individuals that carry them but do not show them (due to their being masked by dominant alleles). Dominant alleles cannot be carried along in a hidden state like this, and if a dominant allele is present it is expressed. Dominant alleles, if present, show up in each generation.
Another interaction of genes is epistasis, which is the ability of specific allelic combinations at certain loci to mask the expression of another locus. It is similar to the relationships of dominant and recessive alleles, but concerns two or more loci instead of only one. The gene that is masked by an epistatic gene (or allelic combination) is referred to as being hypostatic, while the gene or combination causing the masking is called epistatic. Hypostatic genes can pop up as surprises, much as do recessive genes.
Genetic loci can be considered as separate little biochemical
factories. Each locus controls some unique aspect of the final color. Each
locus can be considered to be a switching mechanism. At most loci the
choice is either "situation A" or "situation B". The choice at each locus
will affect the final color, which is built step by step from all the
choices at the various loci controlling color.
Pigments in goats consist of two main types: eumelanin and pheomelanin. These two pigments can be present or absent in varying combinations. Some genes affect only one of the two; others affect both.
Eumelanin is responsible for black-bluegrey-chocolate brown colors. On most goats eumelanin is only one shade, unless it has become bleached by the sun or changed by some other environmental (and therefore nongenetic) factor. Therefore each goat, where it has eumelanin, is all black, or all chocolate brown and not some combination of the two. Eumelanic areas of mohair routinely fade with age so that black kids become bluegrey. This seems to be an exception to the rule that eumelanin is consistent, unless it is considered that black/bluegrey are shades of one color (black). Mohair is a long fiber and black pigment is "stretched" along the fiber length, resulting in a lighter color.
Eumelanin can be chocolate brown instead of black/blue grey. Chocolate brown usually fades to lighter brown on mohair. Brown eumelanin varies from very dark to very light, but the goat is one basic color overall. Eumelanin on an individual animal is always one basic color, either black or brown. Truly brown Angora goats are rare, as most Angoras have black eumelanin. If a colored Angora goat has any black at all, then the choice for eumelanin color is black--not brown. This is especially important when deciding if a goat is brown or red.
Pheomelanin is responsible for tan, cream and red colors. The pheomelanic tans are extremely variable, and unlike eumelanin, they frequently vary on an individual goat. Some goats have dark tan as well as pale cream pheomelanic areas. This makes accurate identification of pheomelanin tricky at times. Pheomelanin can vary from very dark to very light. At the light extreme it is nearly white. At the dark extreme it can be confused with the browns of eumelanin. Generally pheomelanic colors have a reddish tinge. This is in contrast to eumelanin, which (when brown) is usually a flatter brown with little red in it.
The position of eumelanic and pheomelanic areas determines the basic color of goats, and the classification of goat color depends on the specific pattern of pigmented areas. Unfortunately, white spotting can obscure portions of goats, making it difficult (and at times impossible) to appreciate their pigmentation type and pattern.
White regions on otherwise colored goats are not pigmented, and pigment cells are usually completely absent in white regions. This phenomenon is called "white spotting." White spotting is superimposed over any base color and masks it. White spotting can be thought of as painted onto a colored goat and not the other way around. Goats can have many different patterns of white spotting, and each of these is totally independent in terms of genetic control. Even goats with very extensive white spotting do indeed have the genetic machinery, if hidden, for some base color. These hidden color genes of extensively white goats can be just as useful in a breeding program as the more obviously expressed color genes of darker goats.
The final color of the goat is due to the interaction of eumelanin (black/brown), pheomelanin (red brown/tan/cream/white) and white spotting (white).
The control mechanisms for final color suggest two pathways to a white goat. One of these uses the pale end of pheomelanin. Basically, first make the goat totally pheomelanic and then fade the pheomelanin to a very, very pale shade until the goat is essentially white. This is a dilution mechanism, and pigment cells are present in the white areas but are simply ineffective at producing pigment. Another general mechanism to produce a white goat is to use white spotting in which the background color of the goat could be anything, but superimposed over this is white spotting which masks all the color with bright, pure white. White spotting can occur as multiple, independent patterns each of which can result in a white goat.
White can be a very confusing color, since just looking at a white goat
does not tell much about the genetic mechanism producing the white. Part
of the challenge of producing colored Angora goats is to eliminate the
white, and this has proven difficult because the exact mechanism(s)
resulting in white Angoras are not obvious. White Angoras may well be the
product of multiple mechanisms acting together. Once the mechanism for
white Angora goats is fully understood it should be possible to produce
colored ones much more easily.
The genetic control of color in non-Angora goats is complicated, but can be broken down into components that are fairly easily understood. Confusion usually comes from not realizing that final color is the result of the interaction of several different components. Each component resides at a separate locus, and at each locus various choices occur. The sum of the choices made at each locus produces the final color.
Most of the variation in goat color occurs at the Agouti locus. This locus controls the distribution of eumelanic and pheomelanic areas. The intermediate alleles at this locus result in patterns with distinctive striping patterns on the face, and this characteristic is very helpful in establishing the Agouti locus as the cause of these patterns.
The pattern of dominance at the Agouti locus is that all pheomelanic (tan) areas are expressed. When a goat has alleles for two different patterns, each is demonstrated in the final color as the tan areas of both patterns. The patterns are superimposed with all the tan areas being expressed.
Two patterns at the Agouti locus cause difficulties. One of these is the recessive "no pattern" allele, which is completely eumelanic. This is usually black and can be thought of as "recessive black," when considering the Agouti locus. Such goats are completely eumelanic with no stripes, so this is not intuitively assigned to the Agouti locus. At the opposite extreme is an allele "white or tan," which causes wholly tan (or white) goats. Again, stripes are missing. The "white or tan" allele is dominant to all the others, for it codes for a uniformly pheomelanic color. Whether the goat is stark white, almond, dark red or something in between is determined by genes not at the Agouti locus, so these color types are equivalent when considering the Agouti locus.
Multiple genetic mechanisms can account for both solid white and solid black goats, and these differences cannot be determined by just looking at the goat. The Agouti alleles are one of many mechanisms for these colors, and are the usual mechanism in non-Angora goats. Most non-Angora black goats are black because they have the correct Agouti locus allele (Pygmies and black Oberhaslis are good examples). A non-Angora white goat is generally white because it has the "white or tan" Agouti locus allele (Saanens and Cashmere goats are good examples). Other important mechanisms appear to be playing a major role in Angora goat coat color. Wholly white and wholly black goats can be confusing, while those with distinctively Agouti locus patterns (with stripes) are less confusing.
The Agouti patterns, somewhat in order of dominance or degree of tan, are:
Another major source of variation in non-Angora goats is the Brown locus. This locus acts to switch eumelanin from black to brown. This can be dark chocolate brown, light brown or a medium brown (confusingly called "red" by Pygmy owners, but lacking the real redness of the darker tans). The Brown locus does not affect tan colors, only black, and causes any black on the goat to be brown instead. The result, on Agouti patterns, is an interplay of tan and brown instead of tan and black areas. As an example, Toggenburg goats have the "swiss markings" pattern at the Agouti locus with the "light brown" change at the Brown locus. The result is a distinctively patterned brown goat still easily recognizable as having an Agouti pattern.
The alleles at the Brown locus likely include:
Other Color Loci
Other loci that affect color directly are poorly documented in goats. Most species have a number of loci that act to reduce the intensity of tan areas caused by pheomelanin. These modifiers cause tan areas to be pale and can cause the tan regions of the Agouti patterns to be yellow or cream instead of tan. Some of these modifiers are likely to be important in the production of patterns such as the Toggenburg goat on which the pheomelanic areas are so pale as to appear to be white.
Likewise, pheomelanin can be intensified to a deep reddish tan or even a dark red. The shade of pheomelanin can drastically affect the overall appearance of the Agouti patterns. When pheomelanin is very dark and eumelanin is changed to brown it can be very very difficult to appreciate that Agouti patterns are present simply because the "tan" and "brown" areas end up being so similar in color.
Several different patterns of white spotting occur in goats with each under separate genetic control. That is each pattern is controlled by a separate locus. At each of these loci the choice is "patterned" or "not patterned," which means unspotted, unless some other locus kicks in with a pattern.
White patterns in goats, each most likely at an independent locus:
Finally, some goats with white spotting develop small spots of color in the white areas. This occurs with age usually around a year or so. This spotting is called ticking and varies from lots to a little. When "ticks" are numerous, they merge and the effect can nearly be roan. This pattern is a sort of reverse of the "flowery" pattern. Ticking is probably dominant.
Overall Comments on Genetic Control in Non-Angoras
The story for non-Angoras is rather straightforward. For colored goats, it is obvious that they have no white that is masking things and so are not the "white/tan" allele. If the goats are striped, they can usually be assigned into one of the general Agouti patterns. If they cannot, then it is possible that the goat has a new Agouti variant, which needs to be documented and described. Any such new variant should behave just as do the other Agouti variants. The "brown" versus "black" choice is just icing on the cake as an additional source of variation that might be useful to Angora goat breeders.
Angoras break the rules for color production of non-Angoras. One important difference is that some black Angoras, when crossed to striped goats (intermediate Agouti patterns) or to reds (presumably Agouti), are able to produce blacks and whites. This indicates that a dominant black is present in Angora goats. The two different genetic mechanisms working to produce black goats can confuse breeders. One mechanism is dominant (probably at the Extension locus and symbolized ED) and one recessive (at Agouti). The two types of black cannot be distinguished visually and have essentially opposite genetic control at different loci. Both dominant and recessive black appear to be present in Angoras with the result that an occasional black to black mating might result in red or striped kids.
The dominant black is an important and frequent genetic mechanism for black in colored Angoras. Many of these start out life black, then fade to grey on the fleeced portions of the body. They are still black genetically, but the black gets "stretched" along the fiber and ends up being lightened somewhat. Most black Angoras have an undocumented background, so it is uncertain if dominant black originates in purebred or grade goats. It is so unusual in non-Angoras that it probably is hidden somewhere behind the whiteness of the usual Angora and indeed probably originated in the Angora.
Another phenomenon in which colored Angoras deviate from non-Angoras is the occasional production of red kids from striped parents. Since striped parents are expressing Agouti patterns they should not produce red kids, as red is dominant at the Agouti locus. The production of striped kids from red parents is expected at this locus--the opposite is not. This means that the Angora may have a recessive red and, in other species, a good candidate is another Extension locus allele.
Probable Extension Locus Alleles in Angora Goats
Two loci, Agouti and Extension, control similar colors, and they interact in confusing ways. The only certainty is that goats with intermediate Agouti patterns (striped) are sure to have no dominant black allele, and must have at least one wild type allele at Extension.
Red goats could be either dominant at Agouti or recessive at Extension. A suspicion is that the recessive Extension reds are likely to be uniform, while many (but unfortunately not all) of the dominant Agouti reds more likely retain some pattern of a darker backstripe and shoulder stripes. Agouti reds should on occasion produce stripes, but Extension reds, when mated together, should produce nothing but reds.
Black goats are the opposite conundrum being either dominant at Extension or recessive at Agouti. These are likely to be impossible to distinguish visually, and both are likely to fade to grey with few exceptions. Dominant Extension blacks can and should produce reds and stripes on occasion, while mating recessive Agouti blacks together should produce nothing other than black goats (and the possibility of an occasional recessive Extension red). Any black goat arising from two striped parents is assured of being a recessive Agouti black.
The usual white of Angoras is not the Agouti locus allele that causes white goats of most other breeds. The white of Angoras white is epistatic to both Agouti and Extension, which simply means that it covers them up completely. Beneath every white Angora are some hidden pieces of information at Agouti and Extension that might be of use to colored Angora breeders. The white of Angoras is called angora white and symbolized WhD since it is dominant.
It is very likely that the stark whiteness of the usual Angora arises from piling on several genetic mechanisms for whiteness. Each mechanism that could lead to a white goat is probably somewhat "leaky," and might result in some colored fibers. Millennia of selection against those colored fibers has selected for animals that have multiple mechanisms for whiteness all helping to eliminate colored fibers. The different mechanisms all get stacked on the same goat resulting in bright, clean white. Breeders desiring colored Angoras have to disrupt this. Most white Angoras have the dominant allele at the Angora White locus as well as the white or tan allele at Agouti. Colored cropouts from white goats are more likely to be red (usually pale) than any other color. In addition, many goats have white spotting patterns, and the belted pattern is relatively common in colored purebred Angoras.
Other alleles at Agouti, and the dominant Extension black also seem to be relatively common in colored Angoras and provide for more choices of color.
Colored Angoras are of two main sorts:
Each basic color of Angoras suggests a different strategy for breeding.
Striped goats are the easiest colors to breed predictably. They are intermediate Agouti alleles, so striped to striped matings produce all striped kids (with the rare possibility of recessive Agouti black and a rarer recessive Extension red). Striped patterns result in mohair that varies in color over the body, from tan to white in some areas (the pheomelanic areas) to black or grey (in eumelanic areas). This variation is desirable for some breeders, undesirable for others and is almost unavoidable if striped goats are bred.
Though striped goats yield relatively few surprises in the kid crop, the occasional recessive Agouti black from such matings is useful since it fits back into the striped breeding program.
Strengthening vitality or fiber characteristics in striped Angora breeding programs may require the occasional outcross to some other color or line. Red goats should be relatively useful for this since these are usually Agouti reds or tans. The first cross should yield mostly red kids, but using those kids back on striped goats should produce roughly half red or tan and half striped. If the striped goats have very pale pheomelanic areas, it is possible that the first outcross to red will produce white kids. These are not the usual white Angoras, but are instead tan Angoras diluted to white and will behave predictably in a breeding program.
Outcrosses to registered white Angoras are a bit more complicated. The first kids should be white having received the dominant angora white allele from the registered parent. These kids also probably have the white or tan allele at the Agouti locus and are modified to be very pale at this locus. Breeders can use these white kids from the striped x white parents and mate them back to striped mates. The result should be half white from the Angora White mechanism and the other half should express the Agouti alleles. In all likelihood, half of this half ( or one quarter) are likely to be white or tan--very likely white. The other "half of the half" will be striped and this is one quarter of the overall kid crop. In order to take advantage of the white Angora outcross ,it is necessary to raise quite a few kids to have the striped patterns come out again, hopefully with good fiber characteristics.
Most Angoras with striped patterns have eumelanic regions that are black or grey and pheomelanic regions that are white or nearly so. When such goats are paired with goats having the white or tan allele at the Agouti locus, the result is modification to white. Therefore, it is usual for breeding programs to produce combinations of striped and white kids--not combinations of red and striped kids. The combination of red and striped kids is possible though, with the tantalizing potential for goats with reddish as well as black to grey hair on an individual goat.
Black is complicated since both the dominant Extension type and the recessive Agouti type are present in the colored Angora. If a population of true breeding black goats is desired, then the black goats from striped matings are very useful. The reason for this is that such goats are recessive Agouti blacks and, as such, will hold few surprises. Recessive colors rarely surprise the breeder with unexpected colors in the kids. Such black goats could be used in a breeding program much as the striped goats are used.
Dominant black appears to be more common among colored Angoras than is the recessive black. Therefore, breeders desiring the recessive black need to be sure that black goats came from striped to striped matings. Many dominant black Angoras also have the white or tan allele at Agouti. The use of these dominant blacks with striped mates usually results in half black kids. The other half are variable, although reds and whites appear to be the rule.
It may also be worth putting selection pressure on the depth of color in black goats. Very few seem to hold their black birth coat very well and fade to grey rapidly. Both black and grey types are useful for breeders since both colors are in demand in the colored mohair market.
Dominant black goats mated to white Angoras should produce white kids. Those kids in turn used on red or striped goats should produce about one fourth black kids, one half white and the last one fourth either red or white (and likely white).
Tan and red of varying intensity are common colors for colored Angoras. Most goats identified as from registered parents are red of some shade (tan, beige, etc.). Intensity of red is important, because red goats generally fade quite rapidly from the birth coat. Goats that fade more slowly are likely to be very useful for breeding programs. Most red Angoras have their color due to the white or tan allele at the Agouti locus. Many of them appear to have two doses of this allele such that they very consistently produce reds. This can be very useful, as the consistency allows for some selection for depth of color. Rich tans and reds are rare among handspinning fibers, and colored Angora breeders are in the enviable position of having a corner on the market.
One problem with the red goats is that the color does fade, and modifiers that result in the darker range of shades need to be closely managed. Outcrosses set back the color aspect of the breeding program, and managing a population for both fiber quality and color can be difficult. Crosses to white registered goats result in white kids. Those kids used back onto red goats will give variable results, but usually will give mostly white kids with only a few reds. Those few reds are very likely to be at the paler end of the color range.
Occasional red goats have color intensity that varies with the season. Some clips are darker, and some clips are lighter. These goats, when very dark, are also useful for breeding programs even though they defy the usual rule of fading consistently with age.
Brown colored Angoras appear to be reasonably rare. Most goats that are "brown" at birth are really very dark reds. Some goats look undeniably chocolate, yet produce as if they have the white or tan allele at Agouti, and are therefore red. Truly brown goats could be very useful for Angora breeders, including the dominant dark brown, the dominant light brown and the recessive medium brown types. Once such goats are identified it should be possible to propagate these by using outcrosses to black goats. The dark brown is probably the most useful of the types, since the color of all Angoras tends to fade and starting with darker colors results in a darker final mohair color.