
Never have I ever seen such a heated debate as one I saw on Facebook recently. A horse was shown jumping cross country and her owner states that she gets messaged chastising her for calling the mare a chestnut. She is, in fact a sorrel, she was told. A heated debate ensues. Is it chestnut or sorrel!? There was a lot of passion in those replies. Which is right? Who has the final authority on this matter?!
This is not something I would have guessed would be such a heated topic, but people are passionate about what they are calling their red headed equines.
Myself, spending most of my riding life in northern Virginia, have always called them chestnuts. Everyone I know calls them chestnuts. Every horse care book I read has called them chestnuts. At some point, I must have read what a sorrel was, because I knew, and I did see people calling them sorrel when I was in 4-H, but I still called them chestnuts. It seems completely natural to me that everyone would call them chestnuts.
But, based on what I just witnessed, that is not the case. Just as I grew up with chestnuts, others must have lived their own lives calling them sorrel. Sorrel was so ingrained in them that the thought of calling them a chestnut was laughable. I even saw someone say, “Chestnuts aren’t horses, they are trees!!! *laughing emoji*”
So how did we get to this point? Why are their two names? What is going on here!?
Genetics Behind the Red Coat
Let’s start with the absolute facts, the laws of nature that are set in stone and cannot be argued.
The red color in horses is caused by the recessive “e” gene. This gene prevents the production of black pigment in the horse’s hair, resulting in a coat that is predominantly red or brown. The intensity of the red color is determined by other genes, with some horses having a lighter shade of red and others having a darker shade. But the main gene is the same.
Keeping this in mind, there is no genetic difference between chestnuts and sorrels. They have the exact same genetic makeup (in the hair color department, obviously they are different in other ways).
There may be modifying genes that change the horse’s color more, resulting in variations of the chestnut gene, but that’s not what I’m talking about in this post, and that would take a whole other post to discuss.

Differentiating Chestnut and Sorrel
So, genetically, there is no difference, but I have heard other people (and had thoughts myself) of what the difference between chestnuts and sorrels were.
Many people go by using the term “sorrel” to describe horses with a lighter shade of red, while “chestnut” is used for horses with a darker shade. However, this distinction is not always clear-cut, and the terms are often used interchangeably. Some registries have decided to just use one or the other, and some, like the American Quarter Horse Association, considers both terms correct.
As there’s no clear cut answer, the name of the color seems mainly done to regional and cultural differences. For instance, people who ride in an English style discipline typically use the term “chestnut” while those from a western riding background use “sorrel”.
But, it can also be down to regional as well. In some regions, such as the western United States, the term “sorrel” is more commonly used to describe all reddish-brown horses, regardless of shade. In other regions, such as the east coast of America or Great Britain, the term “chestnut” is used more frequently. But, interestingly enough, there’s multiple inns in Great Britain named “Sorrel Horse Inn/Tavern/etc,” which means, aside from looking like an amazing place to visit, also means the term sorrel isn’t specific to the United States. The Anglo-Irish writer Jonathan Switch also has a horse character described as “sorrel,” in his 1726 book Gulliver’s Travels, so the term sorrel has a long history of being used in Europe. It’s believed the word sorrel came from the sorrel plant, which is native to Eurasia.
Ultimately, I have no idea how both terms came into use, but the distinction between chestnut and sorrel is more of a matter of regional usage than a true genetic difference. Both terms are acceptable for describing horses with reddish-brown coats.

So, Which is Right?
Where does that leave us? What term are we supposed to use? Is chestnut or sorrel correct?
I think we’re all going to have to agree to disagree. Just like how soda is called “pop” in some places, we’re just going to have to agree we call the same thing different names.
But just the same, what do you call it? Are you Team Sorrel or Team Chestnut?