Frame Overo

Overo, as a term, covers three distinctly different patterns (at least three alleles of three different genes). The three types of overo recognized by APHA are splashed white, sabino, and frame. Today, I want to type about Frame Overo.

In the frame overo pattern the horse usually has most of these characteristics:

-white spots arranged horizontally on its sides and neck, many also have white spots that spread from the belly up to the back. The white should look like it is inside a picture frame of dark areas along the top line and belly. Almost all have solid color over the backbone from the withers to the tail bone

-clean, jagged-edged spots sometimes with spots within.

-Usually a lot of face white, though they can have normal face markings

solid manes and tails, sometimes a little white in the mane because a spot crossed over the neck
at least one totally solid-colored leg; many have no leg markings, very rarely four white stockings

Many have a dark mustache on the upper lip

-frequently have one or two blue eyes. (I know this is kind of cheating because she is phenotypically a perlino. She is also a frame overo. Her white markings do not encompass her eyes.)

As with tobiano, all the overo alleles are dominant and can hide solid color. There has been frame overos produced by 2 ‘solid’ horses. This would seem like a recessive gene, but both a recessive and a dominant wouldn't control the same pattern. Some of these ‘solid’ horses are actually genetically frame overos without body spots. They still have the gene and can still produce frame overo-spotted offspring. These horses tend to have different or odd white markings.

-The Frame Overo gene is linked to Lethal White. In a nutshell, all frame overos are positive for lethal white, but not all lethal white positive horses are just frame overos. It is common for many Paint horses to carry more than one spotting gene. You cannot tell for sure whether a horse carries the Frame allele just by looking because the horse may also carry a tobiano gene or another type of overo gene. For instance, a frame/sabino overo or a tobiano/overo (tovero).

-I was planning on going into further detail on Lethal White, but I’ve decided to save it and have an entire post about it. I will say that lethal white foals are born with 2 copies of the frame gene and die soon after birth from gut abnormalities.

-Do not breed 2 horses that are positive for the Frame gene to each other. If 2 Frames are bred, there is a 25 percent chance of a Lethal White foal. Testing your horse for Lethal White, before breeding, is necessary in order to be a responsible breeder. The Veterinary Genetics Lab at the University of California at Davis can test your horse for the frame gene.

Tobiano Paint Pattern

Wow. On my last post I wondered where the time went. That was 4 days ago... Irony.

Here is my small Tobiano contribution. I really encourage anyone that may be reading this to visit the aphatobianohorse blog that is linked on the right.

The Tobiano Pattern

This pattern is known to be dominant and is a quite common pattern to see.
The pattern itself, generally, is pretty consistent. Most tobianos have many of these traits:

- a 'war shield' or large spot of color over the chest and shoulders and on each flank; sometimes only one flank spot, and rarely, none.

-facial markings like a solid horse: star, stripe, snip (One of the fun ways to figure out if a horse is tobiano is to picture them with a cooler blanket on up to their poll. If they look like a normal colored horse with 4 whites, they are probably tobiano). Rarely a tobiano will have Overo type markings on it’s face.

-mixed white and colored manes and tails or one of the two.

-spots usually have even, clean, crisp, non-jagged edges.

-spots are arranged vertically with white extending over the topline.
four white legs (few have one solid leg, and even less have 2 solid legs)

-The pattern can be an almost solid horse with 4 white legs and a few white mane hairs to almost solid white with a colored head.

-skin underlying the white spots is pink and under the colored areas it is black, though pigmented skin surrounding a color spot may be overlain by white hair which will cause a cast to the border - like a halo

-"ink spots" in the white patches

-eyes are usually brown but one or both may be blue or partially blue

Tobiano Genetics

The pattern genetics are fairly straight forward. The spotting is due to a dominant gene. So, every tobiano horse has a parent with the tobiano gene. Sometimes, there is a tobiano horse that comes from 2 seemingly solid horses. In reality, at least one of the parents was a minimally marked tobiano that was registered as solid, due to not enough white on the body.

There are 2 terms that are handy to know when discussing equine genetics, Heterozygous and homozygous. Heterozygous means that the horse has only one copy (out of 2) of the gene in question. Homozygous means that the horse received one copy of the gene from each parent, so it has 2 copies. A homozygous tobiano horse will always produce a tobiano foal.

The tobiano gene has two alleles (possible forms in which a gene for a specific trait can occur). The dominant allele, TO, produces the tobiano pattern and the recessive allele, to, is non-tobiano. A horse that is homozygous for tobiano is symbolized as TOTO.
There is a ton of genetic information I could try to delve into here, but that is the basics.
A test has been developed to determine zygosity of tobianos.

Here is some info from UC Davis VGL (website linked at right):

Determining if a Horse is Homozygous for Tobiano

There is no direct DNA diagnostic test available for the tobiano gene, but progeny testing provides the next best information. A horse that produces any non-tobiano colored foals is not homozygous for tobiano. A horse bred to at least 10 solid colored mates that has only tobiano foals is statistically 99.9% certain to be homozygous.

Many horses that are homozygous for tobiano have a secondary spotting pattern of small clustered dark spots with roan edges breaking through in the white areas of the body. These spots, sometimes called "ink spots" or "paw prints" are often, but not always, associated with homozygous tobianos.

As most owners do not want to wait for progeny information from a very young horse and secondary spotting is not absolutely associated with tobiano homozygosity, a test is available that can help predict the likelihood that a horse is homozygous for tobiano.

Tobiano Zygosity Testing

There is no direct test at this time for the tobiano gene, however there are closely linked markers that can be used to determine if a horse carries one or two copies of the tobiano chromosome. Previously, the blood markers, Albumin (AL) and Group-specific component (GC) were used for this linkage analysis. VGL is now using hair samples to test for six closely linked DNA markers, thus eliminating the need for blood samples.

Requirements for Tobiano Zygosity Analysis

The minimum requirement for a horse to be homozygous for tobiano, is that it must have two tobiano parents.

The new tobiano analysis requires the following information for complete analysis:

Pedigree: three-generation pedigree with color and patterns marked

Photos of the subject horse: good quality photos and both sides preferred. Digital photos are accepted.

Where does the time go?

Okay, so I'm not sure how it happened, but the day passed by in a blur of minutes and hours. It is now less than 6 hours from when I need to get up for work tomorrow.

What's really cool (and neatly releases me from staying up much later to finish my Tobiano post), is that Forthefutureofthebreed did a wonderful blog yesterday on Tobianos. There is really very little to add. Here is the link, http://aphatobianohorses.blogspot.com/2007/09/genetics-of-tobiano.html ,in case anyone actually wanders over here and reads this. Aphatobianohorses has all you ever needed to know, and then some on Tobiano characteristics, breeding, pedigrees, pictures, and more. I'm sure the blog will just get even more interesting as more material is added.

I have started to put together a small post on Tobianos, just to feel useful. :) I should finish it up tomorrow, if the day passes by in a reasonable amount of time...

Tomorrow - Paint horse patterns

Tobiano - will cover for sure.. hoping FTFOTB chimes in a little ;)
Overo - might cover, but I want to add in a little about Lethal White, Sabino, splash white and frame, so it may be a separate post
Tovero - will probably come after Overo and Tobiano for fairly obvious reasons

After the patterns I plan on stating my opinion on Solid Paint Breds. There seems to be a lot of conflict surrounding these usually under-valued horses.

Until tomorrow then....

Paint vs. Pinto

I figured that I may as well start off with one of my bigger Pet Peeves. Picture above are 2 Paints and 3 Pintos. I tried to pick pretty obvious differences. Who's who? 1, 3, &5 are Pintos. 2 & 4 are Paints.

Actual dialog of a conversation I had:

Gil (we'll just call him that): Nice colt. What breed is he?

Me: He's a Paint.
Gil: I can see that from his color, but is he an Ay-RAB?

Me: Silent scream inside head... No, he's a Paint.

I can't tell you how many different times I've had a conversation that came close to this. Though the Ay-RAB part was quite new to me. Try to keep in mind we're talking about that colt that is pictured (as a yearling) in the first "post". So, I am going to focus on Paint vs. Pinto.

Paint -

Straight from the APHA.com website:

To be eligible for registry, a Paint's sire and dam must be registered with the American Paint Horse Association, the American Quarter Horse Association, or the Jockey Club (Thoroughbreds). At least one parent must be a registered American Paint Horse. To be eligible for the Regular Registry, the horse must also exhibit a minimum amount of white hair over unpigmented (pink) skin.

Which in layman's terms means one parent must be registered APHA, and the other must be registered AQHA, APHA or JC (Jockey Club).

The APHA has 2 different kinds of registry. One is the regular registry which is for horses that have a "natural paint marking" that falls in the correct areas on the horse's body. "Natural paint marking" has a long definition that is available on the apha website at http://www.apha.com/breed/colorreq.html . The other is the Solid Paint Bred registry. This registry is for horses that do not exhibit enough white to be regular registry, but are from the correct bloodlines.

In short, the Paint horse is now a breed, as opposed to a color.

Pinto -

Straight from Ptha.org :

Contrary to the strict limitations of APHA, the Pinto can derive from a very large spectrum of breed and registry crosses. Although PtHA accepts many approved crosses, it does NOT accept animals with Appaloosa, Draft or Mule breeding and/or characteristics.

...the association only requires a minimum of 4 square inches of white hair with underlying pink skin. In addition, this amount is cumulative, as long as the white lies in the qualifying area. Minimum requirements for ponies and miniatures are 3 inches and 2 inches, respectively.

This white marking also must fall into the specific body areas regulated by the PtHA. Now, I'm sure everyone got this... but let me reiterate... PtHA accepts many approved crosses.

Meaning, that if you have a 'colored' horse or pony, it can most likely be registered Pinto. It doesn't matter who it came from, if it's registered, what breed it is, etc. They classify their horses into 'type' and 'size' groups. They also have a breeding stock registry. The qualifications for this are:

A horse that does not meet PtHA color requirements but has either color within two generations OR at least two Pinto characteristics may be eligible for Breeding Stock registry. Pinto characteristics are: blue eyes, high leg white above knee or hock, white hooves, multi-colored/stripped hooves, pink skin, or collective white in eligible zones, but not enough to qualify for color.

So, basically any backyard horse or pony that has 2 Pinto characteristics.

All regular registry Paints can be double registered Pinto, but not all regular registry Pintos can be registered Paint.

I hope this has cleared up any questions. I don't mind explaining the difference to people, but when they argue with me about it...! GRRRR!