I have been busy with work on the upcoming book, but I wanted to share some good examples of the color shifting found in some horses with the Leopard Complex (Lp) mutation. Appaloosa shows are less common than Paint shows in this area, so I was glad when one was scheduled for the Garrison Arena in nearby Clemson, South Carolina on a weekend that I was free to attend.
The mare above is a shade of warm pewter gray that is very common in appaloosas. I would expect her to test black (E_aa) and negative for dilutions, just as my mare does. What is interesting is that not all black appaloosas end up looking like this. At the same show, there was a jet black leopard. Just why the color shifts on some, but not all, is not yet known, though it does not seem necessary for there to be a true dilution gene present for it to occur.
The change in this guy is more subtle. He might be mistaken for a sun-faded black horse, but look closely at his lower legs. They do not look black, nor do they have the reddish or yellowish tones that are more typical of sunburnt hair. Instead they have a dark chocolate tone. In my experience, that “off” color is even more noticeable in person – especially in natural light.
That brings me to the last horse. This mare may well be chestnut, but I would not be entirely surprised if she was in fact black-based. Her odd tone is present to an extent in this photo, but it was more obvious in person. She would certainly be an interesting one to test.
I would also add that all three of these horses are probably homozygous, and the last two images are good shots to show how homozygous horses have shell-colored hooves on their unmarked feet. My own mare is heterozygous, and as her images (linked above) show she is actually more diluted in color than the first two of these. Whatever causes the shifting, it does not seem to be influenced by whether or not the horse is homozygous for Lp.