I've been getting a lot of questions about highland coat colors. The genetics is so fascinating. And yet, even with all the science, calf birthdays are still always a bit of a surprise!
I'll put some simple explanations first, and then build in a bit of nuance and complexity. And then below I'll link some other interesting and scholarly sources. If you like to geek out on highland coat color genetics and have a favorite source, send it to me and I'll add it to the list!
Going back to hereditary basics
For all of this discussion, you will need to think back to your high school science days of studying genetics and making Punnett Squares. You may recall that mom and dad each contribute a gene to an offspring, and then the offspring expresses that gene combination. By using Punnett Squares and math, you can figure out the probability of each combination occurring.
Take the example to the right, which is a heterozygous black sire and a heterozygous black dam. (Heterozygous means the gene pair is different, in this case one Black gene which is Ed, and one Red gene which is e.) The Black gene is dominant (see below for more explanation of that), so when combined together, there's a 75% chance of producing a black calf and 25% of producing a red calf.
For color genetics itself, the simplistic view of highland coat colors is that there's a color,
which is either dominant or recessive. This gene is called the MC1R. Dominant means that regardless of what other gene is there, the dominant gene takes over. And recessive means that it requires two of that gene in order to express itself. In the example above, Black is dominant over Red, which means that it requires 2 Red genes in order to express a red cow.
To add, there's also a deletion gene that expresses itself with muted or diluted color. This is the PMEL17-delTTC. The dilution gene is dominant, so you only need 1 in order to start expressing a diluted color.
In the world of mini cattle, there's been a lot of cross breeding which also introduces color patterns that we typically associate with other breeds such as British white (solid with colored tips), belted Galloway (colored with white belt), Hereford (solid with white face), etc. I'll tackle color patterns in a different article because that's an entirely different set of complications!
Base color
Visually, there are two primary accepted "base colors" -- Black and Red. Black, written as Ed, is dominant, which means if black is paired with anything else, it will express itself as black. Red, written as e, is recessive, which means you need two red genes in order to express red.
The nuance here is another gene called Wild Type, written as E+, which is also considered a base color. In simplistic terms, Wild Type is ... a wild card. The Wild Type gene allows both red and black pigment, so it tends to visually expresses whatever characteristics come from of the other gene. So when paired with Black the animal shows as reddish black, and when paired with Red the animal shows as lighter red. When double Wild Type, it also shows as red.
The Wild Type gene is required in order to have Brindle and Bus Dubh. However, having wild type doesn't necessarily mean the animal is brindle. There's other genes at play that are not readily testable.
Deletion gene
But the base color isn't the whole story. You have to also consider the deletion gene.
The deletion gene exists for many species. It effectively dilutes a color, which is why it is also called the dilution gene. Black with one dilution is Dun, and with two dilutions is Silver. Red with one dilution is Yellow, and with two dilutions is White.
Note that some places Silver is called Silver Dun. If you look at the color combos, it's basically the same thing.
Coat color testing and interpreting results
Color coat testing for mini highlands is easy. You pull tail hairs so it has the hair root bulbs still attached, attach them to your order form, and mail it in. Generally takes about 2 weeks for results.
These are the top two sources for color testing for mini highlands. Both sites have detailed instructions and links to videos on how to do this. (Note: I have always pulled tail hairs when I do all the baby things. However, I have seen at least one person say they got invalid test results and were told by UC Davis to wait until the calf was older.)
UC Davis Veterinary Genetics Laboratory - This is the most typical go-to because they test both the MC1R (black/red) and dilution (PMEL) so you can get the full interpretation.
Texas A&M Animal Genetics Laboratory - Texas A&M tests simply for black/red/dun coat color. (Note they also have a new test for White Dexter coloration and Park coloration that UC Davis does not have, which can tell you if your HighPark / White Park is homozygous or heterozygous.)
I generally use UC Davis. I find the interpretation the write is sometimes confusing, in part because it is drawn from some other breeds. Here's the layman's interpretation of these results.
This is a yellow animal. It has a red base (wild + red), and 1 dilution gene.
This is a dun animal. It has a black base (black + red) and 1 dilution gene.
This is a dun animal. It has a black base (black + wild) and 1 dilution gene.
This is a silver animal. It has a black base (black + wild) and 2 dilution genes.
This is a white animal. It has a wild type base (wild + wild) and 2 dilution genes.
A note about calf colors
As with many animals, the color a calf looks at birth can change quite a bit as the calf grows. A slate gray calf often turns to dun. A black calf often turns reddish and then back to black. the point here is to be careful about buying a calf based on what color it currently looks like. This is particularly important when there are popular colors like silver and white, which can be hard to tell in a young calf. You don't want to pay a premium for a silver calf, only to have it end up being dun.
To be certain, you can request color testing. Common testing places are UC Davis and Texas A&M, which I'll link below.
There are also other clues you can go off of. A common saying is "the nose knows", which means you can judge color based on the nose. For example, a pink nose typically indicates the calf is red base, which is red, yellow, or white. Similar with the hooves. Pink hooves typically indicates the calf is red base.
A funny comment
I'm really tickled by the AI Title Creator for this post, which suggested these as titles. Which is you favorite? I think next time I list a calf I will identify is as Tartan or Tweed. Lol.
Exploring the Diverse Highland Coat Colors: From Rusty Reds to Stunning Sable Shades
Exploring the Spectrum of Highland Coat Colors: From Rich Reds to Earthy Browns
Exploring the Rich Diversity of Highland Coat Colors: From Tartan to Tweed, What Makes Each Unique?
Resources
Coat Color Basics of Highland Cattle -- One of my favorite sources. It has some great pics of colors of cattle, and discussion and pics about changing calf colors. It also has some charts to help you easily figure out the likelihood of different colors based on dam/sire combinations.
The genetics of Highland cattle coat colours -- This is a more basic article than Coat Color Basics, but it has more pictures and also talks differently about the wild type gene as it relates to brindle.
Heartland Highland Cattle Association -- Identifies the 6 primary colors plus Brindle as a color. This page has links to quite a bit more color-related pictures.
Highland Coat Colour Genetics Explained -- This dives a bit more into genetics concepts, and other color genes that we can't readily test yet.
MC1R Gene - Black / Red -- This article from UC Davis talks a bit more about the MC1R gene, which is where the black/red/wild gene is located.
PMEL17 - Color Dilution -- This article from UC Davis talks a bit more about the dilution gene, which is where you get Dun, Silver, Yellow, and White colors from.