Horse Color Genetics: Identifying Crop-Out Paints

Review: TO=tobiano, O=frame overo, SB1=sabino

One thing that confuses and frustrates a lot of non-geneticists is when they breed two paints together and the resulting baby is completely solid, no interesting pattern at all. But the one combination that totally doesn't make sense to a lot of people is when they breed two non-paints and the baby is paint. How do you explain this, and why does it happen?

As a side note, before I begin, I use paint and pinto interchangeably. In genetics, there is no difference, it is a patterned horse with pattern genes. Some people get into crazy arguements about which is correct, but there is no difference. If you are speaking about which is a breed, then generally Paint is a breed, whereas pinto is a color.

It's important to understand that pinto-patterned horses come in a lot of different varieties. Some are crazily patterned....

Some have only a minimal pattern, but are still obviously paint (well, the one below isn't super obvious, but you get the idea)....

And some don't look paint at all!

I know, you may be gasping, but I'm guessing both of the above horses carry some sort of paint gene. How do I know? And why aren't they as flashy as other paints?

Similar to other markings, all various genes are inherited from the parents. Paints don't just happen, they had to get them from somewhere. 

The horses above are what you might call a 'crop-out' paint. Crop-outs are born from a pinto-patterned horse, but to the disappointment of the owners, they turned out solid. But the difference between a crop-out paint and a solid horse is that a crop-out paint actually DOES have a paint gene in there, the owner just may or may not know it. It takes a little knowledge and practice to be able to identify a crop-out.

In pinto patterns, all paints carry a certain amount of expressing or suppressing gene. Because all horses start out as a base color (chestnut, bay, black), white is added in. Fully expressed pinto horses have more white; some are so white they almost don't look pinto, like the foal below (notice his ears).

While most paints have a more even balance of both, like the horse below

It does seem like there are a lot of paint horses out there, I personally think there are a lot more crop-out paints than most people would think. The horse below is what some people may or may not recognize as a crop-out paint.

So now, the big question: how do I tell a crop-out pinto from a horse who simply didn't didn't inherit any paint genes? 

A minimally-marked pinto will look, well, like the horse above. Tall white stockings are an indicator of pinto, and also the marking sometimes called, 'bald face', where the face is quite white.

Besides double-dilute horses (cremello, perlino, and smoky white), blue eyes are ALWAYS an indicator of pinto. The horse below has no white markings on her legs, but her face marking is rather large. Even though it doesn't cross over her eyes, it is large enough to mark her as a paint. Plus the blue eyes.

The horses below are very unusual; they doesn't have any particular face marking, but their eyes are blue. It's in there somewhere!

Going back to the stockings, some crop-out paints don't have particularly tall stockings. This is one of the horses I posted earlier:

He is super cool. While I can't be positive about his pinto status, what makes me guess that he is a pinto is because of the way that back left stocking has that jagged edge. Very jagged edges on leg markings, whether tall or short, can give you a clue. I don't know whether this is a hard and fast rule or not. And like I said, I'm not very sure on the above horse.

So, back to the very first question: how does a paint produce a solid horse, and a solid horse produce a paint?

They are actually very different questions. The first question, how does a paint produce a solid horse, is not too hard to answer. Just like other genes, unless more is known about the horse, it is safe to assume that there is a 50% chance of the foal inheriting it. If the foal is born solid, then you need to ask yourself whether they are crop-outs, or whether they actually didn't inherit any pinto gene at all. 

The thing about crop-out pinto horses is that they ARE pintos with pass-alongable pinto genes, just not easily recognizable. One problem with the APHA (American Paint Horse Association) is that they don't admit that crop-outs have pinto patterns, and are then labeled as 'solid breeding stock'. But crop-outs can still produce colored babies, unlike true solid-colored horses. While they can still be registered just as any other paint, they are less desirable.

Back to the other question: how can a solid horse produce a paint? Now that you are more informed, you know the answer: that pinto pattern didn't come from nowhere. One of the parents is a crop-out, who is actually not solid.

Going back to the expressed/suppressed pinto genes, that will have to be another post! I'm having a hard time understanding myself how a supressed pinto gene can be hidden for many generations, and then all of a sudden the suppressed gene is turned off and you have a pinto foal.