BUILDING BLOCKS TO COLOR!!

Here is a simplification of equine color genetics that will help the beginner better understand how color works in horses and also how better to identify colors and patterns in horses. Not all the modifiers or dilutions will be covered here, but the basics that are most commonly seen are.

COLOR MATURATION

When foals are born they have a baby coat that is a different color or shade from what it will be as an adult. Sorrel and Chestnut foals are usually born lighter than they will be as adults and their legs and belly's are usually very blond in appearance. Quite frequently this light hair is mistaken for stockings but true stockings will show a distinct line quite early on in most cases. An easy way to be sure if a white marking is present is to wet the leg and see if the skin under the light hair is pink or black. White markings will always have pink skin beneath the hair. Foals have pink skin at birth so you need to wait a week or so before trying to determine for certain.

Bay foals are often born showing very little of the black that will signify it's points later on in life. The best way to tell if a foal is going to be bay is to look at the fetlock to see if there is black on it. Also the knees and hocks will generally show some black hairs even though the legs will often times be very light in appearance to begin with.

Black foals are often born looking gray, brownish black, or black with silver or white guard hairs. Not many foals are born real black looking all over. There are two types of black and both mature differently but will look black at maturity.

It takes three to five years for most coat colors and patterns to fully mature and in the case of gray and the Appaloosa patterns the coat color and pattern change for the entire length of the horse's life.

Champagne foals are usually born DARKER than they will eventually be. They shed lighter and retain a dilute skin color. The skin may be pink, tan, or light gray. Some are mottled or freckled in the skin. Champagne horses also have diluted eye color which is most commonly amber but may be green or gray. Champagne horses have reversed dappling with the dapples being lighter than the coat color.

When horses are mated each parent contributes ONE full set of genes to the offspring. The offspring then receives two copies of every gene. In color, when both parents contribute the same gene such as red, then that horse is termed HOMOZYGOUS for that color. That horse can then only reproduce that color because it has no other choice available. When each parent contributes a different gene then that horse is termed HETEROZYGOUS for that color. That horse can then contribute EITHER color gene to it's offspring.

All horses have to either be heterozygous for a color, or they have to be homozygous for the color. To determine which they are there is a test available. The test will tell whether the horse carries one or two copies of red or black.

It does NOT matter what color the grandparents were because the colors do not skip generations. They do appear to skip generations however. The color of grandparents may be helpful when trying to determine base colors of horses that are dilute or modified such as gray, champagne, or in some compounded colors where more than one dilution is present.

To determine horse color one must FIRST determine the base color of that horse. It will be either red or black. From that base you can then determine what dilutions or modifications may be present by it's own appearance, the parents, and in some cases the grandparents.

THREE BASIC TYPES OF COLOR GENES

When a dominant gene is present the horse will always be the color of that gene. The color "BLACK" in horses is a dominant gene. A horse carrying the black gene will always look black whether it has one black gene (Heterozygous) or two black genes (homozygous). Heterozygous black horses have one red gene and one black gene so they can produce EITHER Color in their offspring. Homozygous black horses can only produce black foals no matter what they are bred to.

Recessive genes ONLY express (show) when in the homozygous state. Both parents must contribute a copy of the same recessive gene for the foal to express that color. The color "RED" is a recessive gene. If a horse is red then it is automatically a recessive homozygote and therefore can ONLY contribute a red gene to the next generation. When only one copy of the recessive gene is present (Heterozygous) the horse will always look the color of the dominant gene. Therefore if a horse has a black gene (dominant) and a red gene (recessive) that horse will always appear black.


Polygenes are genes that require the assistance of other genes in order to
fully express. The resulting appearance will vary depending upon which helping genes are present. Sabino is thought to be a polygene therefore it can express in many different ways to many different degrees depending upon how many helping genes are present. Because there are distinct patterns that form routinely under the Sabino Gene it forms a complex of patterns.

In minimally expressed sabinos the lack of helping genes may restrict the horse from developing more than just common markings. If neither parent contributes the needed helping genes for fuller expression, then the next generation cannot develop fuller patterns unless the mate brings the helping genes back into play.

The Leopard gene that creates the various types of patterns commonly called Appaloosa, is also thought to be a poly- gene and forms a complex. The type and number of helping Genes present determine what pattern the resultant foal will have.

The helping genes for the polygenetic patterns are each transmitted independently Therefore a foal may inherit a pattern different from either parent.

COLOR MODIFIERS AND DILUTIONS

There are only TWO basic colors in horses (true white excluded). The two basic colors are RED (recessive) and BLACK (dominant). ALL OTHER "COLORS" ARE EITHER DILUTIONS of or MODIFIED from those two basic colors.

Think of these two things like this. Dilute colors are like what occurs when you pour cream into coffee and stir it up. You cannot tell where the cream starts and the coffee ends because it all becomes one. With dilute colors the hair itself is lightened to a paler shade of the base color so you will not see the base color at all.

Now think of the Modified colors as sprinkling sugar or salt on a colored mat. You still see the colored mat but the salt or sugar coats it in a way that makes the overall appearance lighter. Light modifiers such as roan or sabino add white hairs to the coat. They mingle with the base colored hairs to produce an overall lighter appearance to the coat.

Dark modifiers work similar to the light. Think of sprinkling pepper on a mat. The color of the mat is still there but the pepper makes it appear darker. Sooty is a dark modifier and can be found on any color horse with the possible exception of champagne, maximum white sabino, or dominant white. It can be seen minimally in perlinos, cremellos and though muted may deepen the tone of the body hair or form dapples.

DILUTE color is a color that has been altered itself. The pigment within the hair shaft has been altered so that it no longer is as strong or deep in hue as the basic hair color. Some color dilutions can work to dilute all colors while others only work on one specific color or area of the body. Some examples of dilute colors are palomino, smoky black, buckskin (from one copy of the cream gene) cremello, smoky cream, perlino( from two copies of the cream gene); amber champagne, golden champagne, classic champagne ( from one copy of the champagne gene) Ivory champagne ( from either two copies of the champagne gene or one copy of champagne AND one copy of cream); Red, yellow, silver, coyote Dun, grulla, (caused by one or more copies of the Dun gene) Agouti which dilutes only the black on a black horses body to make that horse a bay. And finally Silver dapple which also only expresses on black but can be carried in red horses.

MODIFIED color are colors that appear different due to the mixing of white, light, or darker hair with the basic hair color. Some modifiers only act on mane, tail and point colors while others work on the entire body color.

Examples of modified colors are true roan where the body color of the horse mixes about 50/50 with white hairs, Gray...although this is really a dilution of hair color it falls under the Modified rule because eventually the hair of the horse will all turn white.; Sabino, white hairs will mix with base color to varying degrees which can cause only a light ticking or full blown roaning but in sabino roans the face and lower legs will also be roaned.

Some examples of Modifying genes are:

ROAN, GRAY, AGOUTI, SOOTY which adds dapples, darker hair on knees, hocks, bony prominence of the face, and can make entire body coat darker including manes and tails;

Examples of dark modification are Black Bay, Sooty palomino, sooty buckskin, or any other color that is dark due to the mixing of dark hairs along with the basic hair color. Often this modifier will cause dark dapples to appear, barring on the legs, shoulder and counter shading on the back. Dark modifiers are usually called SOOTY, or SMUTTY. They can also cause such things dark smudges on the boney areas of the face.

SPOTTING PATTERNS

There are four basic spotting pattern genes: Tobiano, Frame, Splashed White, Sabino.

Early in embryonic life all foals are white. Pigmentation begins at the stem cell and works along the spine then down the trunk of the animal until it is all colored. When this process is interrupted the result is that area where the pigmentation did not occur will remain white.

There are four specific genes that cause these interruptions to occur and each one acts in a way specific to itself.

TOBIANO horses when they are pure of other spotting genes, tend to have little white on the face and legs. They will have crisp edges to the patches of color and the body will generally be 50% or more colored. Today in the Paint horses and other breeds many of the horses called Tobiano actually have more than one spotting gene present but because the registry will only recognize one pattern on the papers, Tobiano is used exclusively unless that horse looks more like one of the other patterns. Tobiano's will always or almost always, have some white cross over the spine. Tobiano is a DOMINANT gene. If it is present it must express itself, but it can express so minimally that it goes undetected. Some minimal Tobianos will only have perhaps a small sock with ermine spots in it as an indication of the gene's presence.

True Tobianos usually have solid faces or at best minimal face markings. Tobianos also tend to have solid colored legs or minimal white on the legs. In the Paint breed, as well as in the Fox Trotter and Tennessee Walking horse the addition of Sabino and other spotting patterns have melded to make Tobianos appear to have louder markings. Once the two genes merge they generally reproduce together as well. Whether this is a partial mutation is unclear at this time.

OVERO IS NOT A COLOR

After Tobiano are a group of patterns commonly and very MISTAKENLY termed "OVERO". There is no Overo gene and therefore the term is very antiquated and should be abolished because it causes a good deal of confusion when it comes to identifying spotting patterns. Because of this antiquated term most people do not understand that what is termed "overo" incorporates three totally unrelated genes representing distinctly individual patterns which have their own set of "rules" and in some cases problems.

The three patterns which are mistakenly termed "overo" are Frame, Sabino, and Splashed White.

FRAME horses tend to have a lot of facial white but their spots are generally limited to the sides of their body leaving their back and belly colored. Therefore the color forms a "frame" around the white. Smaller spots on the neck will be surrounded by pigmented skin. Frame horses often have blue eyes. Frame pattern is the ONLY PATTERN to cause Lethal White foals and then only in the homozygous state. A foal MUST receive the OLW gene from BOTH parents in order to be a Lethal White. A simple test can be made to see if a horse carries the OLW gene. IF it does, then by simply breeding it to a OLW negative horse you eliminate the possibility of producing a Lethal Foal.

Frame is a DOMINANT gene but it can express so minimally as to go undetected. It is unclear at this point what the most minimal expression is for this gene because some solid appearing horses test positive for OLW which means they carry the Frame gene.

SPLASHED WHITE horses are horses who appear to have been dipped in white paint. Their markings are very clean cut and usually quite level looking rather than sharply pointed or lacy at the edges. Splashed white horses are basically white on the bottom half and colored on the top. Facial markings are usually bald or apron faces but the top of the markings are usually clean cut horizontally often leaving the ears and skull cap colored. Legs and belly markings are usually very even and lack irregular edges. There is a connection between deafness and the Splashed White pattern and of all the spotting patterns Splashed White is the most rare. It is unclear whether Splashed White is a dominant or recessive gene or perhaps a poly-gene.
Not all horses with sharp lines or flat lines of color are splashed white! It takes more than just a face or leg marking that is level to make a horse a splashed white!

SABINO is thought to be a poly-gene which can cause as many as 19 or more specific patterns forming a complex. There are also many variations or mutations of the Sabino gene that have been identified.
Depending upon how many and which helping genes are present, Sabino can express any way from just a solid horse with a few scattered white hairs all the way up to a solid white (viable) horse with dark eyes. In between those two extremes are a host of patterns such as common white markings, high white markings, belly spots, sabino roan, loud sabino (spotted) and medicine hat.

Today, many Sabino horses are mistaken for Frame, Splashed White and even Tobiano because Sabino can mimic all of those patterns. Perhaps the most commonly recognized pattern for sabino is the high white or loud patterns. The high white pattern is what you see in the Clydesdale Budweiser team where the horse has long stockings over the knees and loud facial white.

In most instances Sabino horses have irregular edging to their spots and there will generally be some roaning involved in the colored areas of the pattern. That roaning may range from just a few scattered white hairs to fully roaned patterning and in some cases the roaning can be so extensive as to make the horse nearly white in appearance.

One mutation of Sabino, particularly found in Arabians, often produces sabino patterns that are very crisp and lack roaning. The edges to the white markings are sharp rather than irregular or feathered.

Sabino is the most prevalent of all the spotting genes and yet the least recognized or understood. When Sabino is present along with another spotting gene it will nearly always add white to the pattern of the horse.

Typical pattern markers for sabino will be long white stockings that sometimes run up over the knees or hocks and often come to a point. Disconnected lightning strikes on the upper leg, leg spots, belly spots and white on the head that runs down to the lower lip, chin or under jaw. Roaning or ticking is nearly always present but may not show up until the horse is mature.

In less typical patterning, however, sabino can express in quite a crisp fashion with sharper edges to the spots and more even leg markings.

Research conducted recently has identified at least one form of sabino. There is a test for the SB 1 sabino pattern now available. The "high white/roaning" genetic marker has been identified but so far only one mutation of the sabino gene has been located. The research done on the SB1 gene has shown, however that there are at least 5 variations or mutations of the sabino gene in modern horse. The SB2 test should be available in a relatively short time. There is a mutation called Draft, a specific mutation in Arabians, and one thought to be in Thoroughbreds that differ from the SB1 type even tough they can produce similar patterning. Homozygots for the Sabino gene have been identified.

Today in the gaited breeds, Paints, and some of the Spanish breeds, Sabino is mixed with other patterns or mistaken entirely FOR those other patterns. In particular Splashed White or Frame. In part this is the fault of breed registries that only allow one pattern to be identified on the registration papers.

White foals born from Sabino action are totally viable and healthy yet each year many are destroyed from being mistaken as Lethal Whites Frame.

ANOTHER SPOTTING GENE

There is another spotting gene in horses that is different from the "Pinto" or "Paint" patterns. This gene is the LEOPARD gene. The patterns caused by the Leopard gene are typically called the Appaloosa patterns. Similar to the Sabino gene, the Leopard gene is thought to be a poly-gene and forms a complex of a variety of patterns. Snowflake, Varnished roan, Blanket, and Leopard patterns are a few of the more common Appaloosa patterns caused by the Leopard gene.


Horses with the Leopard gene often display mottled skin, striped hooves, and sometimes a white sclarea around the eyes and may be born solid color only to pattern out as they mature.

 

 

 
 

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