Copyright, 2007
This might seem like a silly question - aren't all Gotland Sheep grey? In short, the answer is yes. However, in North America, Gotland sheep are being bred up using 9 different Foundation breeds: Shetland Sheep, Finnsheep, Icelandic Sheep, Border Leicesters, Blue Faced Leicesters, English Leicesters, Cotswolds, Lincolns and Wensleydales. Within these breeds, most of the colors, patterns and spots possible in sheep are found - most of them within the Shetland and Icelandic breeds! So, even though Gotland sheep are grey, it is possible to get many different colors, patterns and spots within the North American Gotlands, especially in the lower percentage animals.
Color is controlled by four sets of alleles (four loci): color alleles, pattern alleles, extension alleles, and white spotting alleles. The color locus has only two genes, black and brown, so all sheep are either genetically black, or genetically brown. The pattern and extension genes control whether or not and how the color genes are expressed, and how two types of pigment (eumelanin and phaeomelanin) interact.
So, all sheep are either Black or Brown. Yes? Yes. Even a "white" sheep is genetically black or brown. White is actually a "pattern" and not a color, and just "turns off" the basic black or brown pigment of the sheep. Black is dominant, and brown is recessive. This means that a sheep can look black but be able to produce brown offspring, if it inherited the brown gene from one of its parents.
This photo shows the basic colors: black (with sunbleached tips), brown, and white. Although the underlying genetics might seem straightforward, it is not. Two white sheep can have black, brown, or spotted babies; two black sheep can have white babies, etc. The purpose of this paper is to help you understand how this can happen, and what it means for the Gotland upbreeding program.
Black is dominant over brown. In genetics notation, a black sheep is BB/BB when it doesn't carry brown, or is BB/Bb when it does carry brown. A brown sheep is Bb/Bb. Each letter pair is inherited from one parent. The table below summarizes the phenotypes and genotypes of the B locus.
| Phenotype (Sheep Color) | Genotype | Can produce Brown? | Can produce Black? | Homozygous? | Heterozygous? |
| Black | BB/BB | No | Yes | Yes | No |
| Black | BB/Bb | Yes | Yes | No | Yes |
| Brown | Bb/Bb | Yes | No | Yes | No |
Gotland grey sheep are "black" sheep, with their color modified by the pattern gene (to be discussed in the next section). White fibers intermix with the black fibers and makes the overall appearance look "grey". With our North American genetics, some of these "black" sheep will be able to produce "brown" offspring. If the dam is a "moorit" (brown) Shetland or Icelandic sheep, the 50% Gotland lamb will carry brown and be able to produce it when paired with another sheep that carries brown.
As previously stated, a (black) 50% Gotland sheep with a brown dam is BB/Bb, able to produce brown. What is the genetic notation for the 75% Gotland offspring of this brown carrying sheep? Because Gotland sheep in other countries have been purebred for many decades, they are most likely BB/BB. With a homozygous (matching pair of BB alleles) sire, the 75% offspring could be either BB/BB or BB/Bb, inheriting one pair of "B's" from each parent. (Dad only contributes a BB, Mom can contribute either a BB or a Bb.) There is no way of telling for sure by looking at the (black) sheep. It has a 50:50 chance of carrying brown. Sometimes this recessive gene can be carried for many generations and won't be discovered until two brown carrying sheep are mated and produce a brown offspring. At that point, you have a ram in your flock that has passed a brown gene to half of his offspring, in addition to a ewe line that carries brown. Each generation that passes has a lesser and lesser chance of carrying brown.
| Generation | Color | % Gotland | % chance of BB/Bb |
| Brown Foundation Ewe | Brown | 0% | (is Bb/Bb) |
| First Generation | Black | 50% | 100% |
| Second Generation | Black | 75% | 50% |
| Third Generation | Black | 86.5% | 25% |
| Fourth Generation | Black | 93.25% | 12.5% |
| Fifth Generation | Black | 96.625% | 6.25% |
As shown in the table, the chance of carrying brown dimishes fairly quickly. However, although a 5th generation animal has only a 6.25% chance of carrying brown, if it does, 50% of its offspring will carry brown. If this animal happens to be a ram that you buy for breeding purposes, you will automaticaly introduce the brown gene into 50% of the lambs he sires! (and as we know, this is not very helpful if you are trying to develop a flock that breeds true; one heterozygous ram can undo generations of selection!). We will have lovely, registered Gotland sheep in the third generation. With a brown great granddam, they have a one in four chance of carrying brown. Brown can also be introduced unknowingly into your flock from a black foundation ewe that carries a hidden brown gene.
Is that enough Black/Brown? This discussion forms the basis of the pages that follow.
The next page discusses the "Pattern" portion of sheep color.