Horse Color Genetics: Leopard Complex, Part 2

Review: E=black, A=bay, G=gray, CR=cream, D=dun, TO=tobiano, F=flaxen, Z=silver, O=overo, SB1=sabino, SPL=splashed white, LP=leapord complex (appaloosa).

The first thing you need to know about the leapord complex is that it is an incomplete dominant. I know I've maybe mentioned simple and incomplete dominant before, but here is what it means. Simple dominant means that whether the horse has one or two copies of the gene, it will do the same thing. Incomplete dominant means that if you have one gene, it may look different than the horse with two.

With leopard complex horses, just by looking at them it is easy to determine whether they have one dominant LP gene or two. It is actually more simple than you might think. LP horses with spots are heterozygous (one dominant gene), LP horses with no spots (coats like few spot or snowcap) are homozygous (two dominant genes). 

One other thing that is important to know is that all horses with the LP gene are varnish roan underneath. Remember my last post? Anyway, depending on what pattern genes you get, it probably won't show that much. But if you look at the face of the horse's, you can kind of see the roaning in where there are larger patches of dark. This isn't really true of blanket appaloosa's (you can't see the roaning so much), but the presence of the white hairs to make it roan (varnish roan) will be mostly diluted.

For example:

This horse is heterozygous LP. How do I know that? She has spots! Easy. There is a 50/50 chance she will pass the spots onto her babies.

And this one:

 And this one:

They all have spots! Regardless of whether they are all over, or are only on the blanket (or both!), they only have one dominant gene. What could happen if you bred the next two horses together? (Hint: both are heterozygous, or LPlp)

Here are the resulting options:

Surprised at the last one? The different options for the first two horses to have were: LPLP (homozygous; the first horse), LPlp (heterozygous, the second one), or lplp (homozygous recessive, or not present at all).

Now on to homozygous colors. Review: homozygous means you know the horse has two dominant copies of a certain gene. 

Here are a couple horses that are homozygous:

 There is a lot of white. The first one is a snowcap, and the second one is a fewspot (literally!). These horses are homozygous. If you bred those upper two together, what do you think you are going to get? The baby won't have any spots, unless it is a few spot. 

If you remember back to my last post, the last color I mentioned was varnish roan. Varnish roan is the only LP color that is hard to tell; you may not be able to at all without sending your horse's DNA into a lab.

The last thing you may be wondering is, 'How can I tell what pattern my mare's foal will be?' Well, the tricky thing is, you can't. If it might be heterozygous, you won't be able to tell if it will be leapord or blanket. If it is homozygous, you won't be able to tell if it is few spot or snowcap (pray for a snowcap!).

One last fact that is something scientists only recently discovered. Horses that are homozygous for LP have something called CSNB. This stands for congentical stationary night blindness. A mouthful? It is exactly as it sounds: horses that are homozygous are blind in the dark. Surprised? 

You may say, "but my horse sees just fine in the dark!" I'm sure you know your horse very well, but thing is, it probably doesn't. But he doesn't know that. Can you see in the dark? Not very well. Same thing with him. If you couldn't see in the dark, and then someone told you that everyone but you sees in the dark, what would you do? You've always been that way, and there isn't anything you can do about it.

 He has always been that way, and always will be, and he won't know anything different. He has developed ways to get around pretty well in the dark on his own. There isn't anything you can do about it, and I wouldn't really say it is a bad thing to have either. I wouldn't not breed my two homozygous horses together to prevent it, even though it is inevitable to happen.

In conclusion, if you want a spotty horse, breed a  homozygous LP horse with a homozygous recessive. That way, you will have lots of color! In the Appaloosa and Pony of America registry, if you cross with certain breeds, then it is still eligible for full registry. These crosses include: Quarter horse, Arabian, Morgan, and Thoroughbred. Some spotted horse breeders keep these breeds so they can make more color and crazy spots.