possible colors for Zenyatta andTapit foal

edited March 2012 in Zenyatta
Color genetics in horses works something like this: there are two basic body colors in horses ie brown (like Z) and chestnut (like Secretariat). All horses will exibit one of these underlying body coat colors. Brown is the dominant color and chestnut is recessive. On top of these two basic colors there are a number of other factors which may come into play. One of these is the gene for graying which is dominant. The grey foal starts out either chestnut or brown and becomes greyer and greyer over time. Young greys may be very dark and exhibit lovely dapples (like Spectacular Bid)-but these will fade with time until the coat is nearly white. Often the older grey horse will have evenly spaced flecks of its original body color and is then called "fleabitten grey". Hansen (by Tapit) is a rare example of a grey that is nearly white at the age of three. Because grey appears to be dominant, at least one parent must be grey for the colt to be grey. This is true of the dominant basic color brown as well. Because chestnut is recessive, a horse may carry this gene without showing this color. If Tapit and Zenyatta both carry a "silent" chestnut gene their colt COULD be chestnut. If Tapit sires any chestnut foals this shows us that he carries the recessive chestnut gene. Zenyatta quite likely carries two genes for brown (from looking at the colors of most of her relatives for several generations) but if she has just one chestnut foal this will prove me wrong. I suspect the Tapit baby we will be waiting for will be dark brown with a 25% chance of greying. What do you think?

Comments

  • This is really interesting, thanks. I do believe that the future Z/Tapit foal has a 50% chance of being gray, depending on which allele the baby inherits from Tapit.
  • Tapit is heterozygous for gray (from his mom). There is a 50% chance the baby will be gray. He has sired gray, bay, brown, and chestnut foals, so he carries chestnut. Zenyatta may carry it as well. Street Cry has sired chestnuts, and Zenyatta's half-brother Souper Spectacular is chestnut. There is a 2/3 chance that Zenyatta carries it (she could be EE, Ee, or eE).

    The base color, BTW, is not brown but black. True black Thoroughbreds exist but are fairly rare. Most TBs carry the dominant agouti gene A, which removes pigment from the body hair but not the extremities, mane, or tail, yielding a bay horse. Another form of agouti, At, is believed to be responsible for the "dark bay/brown" coloring exhibited by Zenyatta, Bernardini, Street Cry, et al. It is thought to be recessive to A but dominant to a. A true black horse must be aa.
  • AlexAlex Member
    This is interesting. I will have to find some time to read into this. Thanks....
  • This is fascinating! I've studied genetics and read a lot about dog and cat fur color genes but never for horses. Is there a way visually to identify a truly black Thoroughbred? Are there any that someone could name for me? Ruffian was very dark but even she was not true black if I remember correctly.
  • carolinarkansascarolinarkansas hot springs, arkansasMember
    Sunday Silence is listed as dark brown/bay but his biography says that in fact he was a true black ...
  • The only sure-fire way is to do a genetic test for black. A dark bay/brown will have lighter hair on the muzzle, flanks, and belly even if the rest of the horse appears black, but these are sometimes hard to see. A true black will not have these light areas. To add to the confusion, some black horses fade in sunlight, giving them the appearance of a dark bay at certain times of the year. Kelli pointed out on another thread that true black TBs, while rare, are probably more common than we realize. The Jockey Club sometimes registers them as dark bay/brown even when they are not. She cited Sunday Silence and Devil His Due as horses that are registered as dark bay/brown when they are most likely true black.
  • Actually the 2 basic colors are brown and black. Zenyatta is probably black, bay is a form of black where the mane, tail, and lower legs are black but the body color is lighter. Brown is where the entire body is "the same" color. I am not sure if Z's mane and tail are truly black or not so she could be brown or black. Black (bay, dun, buckskin) is dominant, just like brown eyes are dominant in humans. Brown (chestnut, palomino, etc.) is recessive. Then there is the graying factor. Gray horses are born dark and gradually lighten. Roan horses are either black or brown (see above definitions) with white hairs interspersed throughout their coat. They basically stay the same color their entire lives without ever really getting lighter. To know what color Tapit originally was, you would have to see a foal picture. I believe that he was bay with the gray factor. If so, and Z is bay, then their resulting offspring would in all probability be bay/gray. If she is brown then the offspring have a 50/50 chance between bay and chestnut, still possibly turning gray. For a horse to turn gray, one parent MUST be gray.
  • For some reason I feel this foal will be a chestnut....I can just feel it.....
  • @Springsmom83, Zenyatta is what is sometimes referred to as "seal brown" and sometimes as "dark bay/brown," which is the designation used by the Jockey Club. Her base color is black, modified by an agouti gene At. She is a dark brown color and has the easily discerned light areas on her muzzle and flanks that distinguish her from a true, solid black. The Jockey Club uses "chestnut" to designate ee, wherein the only pigment produced is pheomelanin, which produces yellow to red-brown pigment. (If you call a TB brown, it will be assumed you mean dark bay/brown.)

    Tapit may be ee (chestnut base). I thought he was bay also, but all his bay and brown offspring seem to come from bay and brown dams. Plus, he has a lot of chestnut offspring. I haven't found a good foal photo of him yet. Other photos are inconclusive. His stallion conformation photo shows some faint reddish color on his legs and his tail. OTOH, in a 2004 photo taken when he was racing his mane appears black to me, but it is hard to tell for sure.

    I saw a great picture of Hansen as a foal, taken after his foal coat had shed out but while he was still with his mother. He was almost white even then, but his mane was pumpkin orange!
  • I say there is no such thing as a good horse with a bad color. We all have our favorite but any off spring of Zennie will be wonderful..Sherry
  • Agreed, but it is fun to speculate.
  • fun to think about but I hope its a grey
  • laurel_cincinatti,
    Thanks. I saw a picture that was supposed to be of Tapit as a yearling, he had a blaze and 3 white stockings but his knees, hocks, and his mane were dark at that time. His tail was already so light that it was hard to tell what color it was. Because of the knees/hocks, I would think that he was born bay. Unbridled's dam was heterozygous because she was by a bay and out of a chestnut. Tapit's dam was gray, out of a gray, with gray mares going way back. Raise a Native / Native Dancer have a tremendous amount of chestnut in their background along with gray. The chestnut on Pulpit's side is too far back probably to help with color. Zenyatta has enough chestnut up close for it to be possible for her to have the chestnut gene, all gray on her side is 5 generations back with Native Dancer (who was loaded with chestnut genes).
  • Yeah finally,!
  • In the Quarter Horse registry for a horse to be called bay, the body color would be significantly lighter than the mane, tail and legs. A horse like Zenyatta would be called brown. A horse like Uncle Mo is bay. Quarter Horses have a much wider range of colors than TB's. I do not believe true roans exist in TB's, they are actually grey. Roans are born roan and stay unchanged. Horses that are called chestnut like Secretariat would be called sorrel if it was a Quarter Horse. For Quarter Horses, chestnut denotes a color that TB people might call "liver chestnut" (sort of the color of a chocolate labrador retriever). TB's also lack the dilution factor that causes an otherwise bay or brown horse to be buckskin or an otherwise chestnut to be palomino. Quarter Horses have a color called grulla as well (a fairly rare color) in which each hair is alternately banded yellow and brown making the horse appear "mouse" colored. (It doesn't sound pretty but it is). These horses do not change color with age. Duns are horses of any color that have a darker dorsal stripe-these do not appear in TB's either. Sorry to go on but I don't know why TB registry is calling greys "grey or roan" since they are easily differentiated.
  • The Jockey Club is a little behind the times as far as coat color goes. You are right--"gray or roan" should be just gray. The designation has been around for many decades, and I guess when they started using it nobody knew there was a difference.

    There actually are a few dilute TBs out there. A few TB breeders specialize in fancy-colored Thoroughbreds, although they mostly breed for the sport and halter markets. You can find palomino, buckskin, cremello, smoky black, and perlino TBs, as well as various Paint patterns. One of these latter, an overo TB named Sato, has been immortalized as a Breyer horse. He was a guest of honor at the last Breyerfest, IIRC. He is gorgeous. I have no idea what the Jockey Club does with some of them. Sato is registered as a Palomino.

    Hre's an article about a paint-patterned TB now in race training in the UK:
    http://www.metro.co.uk/news/894003-patch-perfect-skewbald-thoroughbred-prepares-for-horse-racing-debut

    You can also find a few true white TBs. Dominant white seems to arise spontaneously every so often in the population. There's a white mare named Patchen Beauty whose third dam, White Beauty, was the daughter of a chestnut and a bay. Patchen Beauty has had several white foals. One of her sons is in the "Breeds" barn at the Kentucky Horse Park as the TB representative--at least he was last year. Another pure white, Yukichan, was a successful racer at the graded stakes level in Japan. Her dam, also white, is a daughter of Sunday Silence, who was registered as dark bay but who was probably true black. Yukichan is known as the most beautiful horse in Japan. Her white full sister, Marshmallows, recently made her racing debut.
  • LisagLisag Member
    I think Chestnut would be cool for The Princess of Zenyatta and Zapit. O, how cool is that, their names together like that..a real cool typo..sorry Tapit.
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