In previous months, most of the featured horses have been born with a "brindle" pattern apparent at birth (Dunbar's Gold, Pocos Scooter Bar, Snips Tiger Miss - pictures in the slideshow if you missed them). However, not all types of brindles are born with a visible pattern. Our featured horse this month is Ima Star Candy Bar, a 1995 AQHA Grullo colored filly out of the brindled buckskin mare Ima Star Moon Bar (picture also in the slideshow). "Candy" gets her grullo color and dun factor markings from her sire Miracle Moon, a grullo (blue dun) AQHA stallion, SI 102, and a sire of AQHA ROM and ABRA World and Reserve World champions in a variety of events. However, "Candy" also received brindling from her dam, making her an example of the combination of "brindle and dun" like Pocos Scooter Bar (see previous month's text - link at bottom of page).
However, "Candy" was not born with the brindle pattern apparent at birth as "Pocos" was. From the composite picture below, you can see the progression of her brindle pattern developing from birth up until 2 years old. Candy is a lighter shade of grullo (silver grullo) than "Pocos" (slate grullo/lobo dun), and therefore her brindling will probably not become as dark as "Pocos".
This seems to indicate there may be different variations of "brindle" which may have a similar outward appearance (phenotype), but are caused by a different genetic action. There are "brindles" which are born with the pattern, and "brindles" which develop the pattern later. They could possibly be variations (allelles) of the same gene, or could be caused by different genes at a different locus entirely. Modifying genes to the main gene might also account for for differences in the pattern.
There is not much genetic information available on striping for horses, but in mice, there are at least 6 different locus which produce striping patterns (usually called mottling in mice). At the "A" (Agouti) locus, striping has appeared in viable yellow, mottled agouti, and agouti suppressor mice. At the "C" locus, striping has appeared in chinchilla mottled mice. At the "P" locus, striping has appeared in pink eyed mottled and p unstable mice. Striping has also appeared in mice at the "Silver" locus, and "Pearl" locus. Striping also appears at the "Mo" locus (responsible for Mottled, Blotchy, Dappled, Brindle, and Tortoiseshell patterns), and the nearby "Ta"(Tabby) locus. Whether any of these genes may be similar and account for striping patterns in horses remains to be determined. Anyone with access to current information on coat color genetices in mice, could be of help. I need to get updated, and find out if any of the above locus have been sequenced yet.
Volume 1, number 8. Written information was last updated September 1, 1997. We will update the written information approximately once a month - however, because Brindle Horses are so rare, we may not be able to update the photos in the slideshow that often. When returning to this site, remember to select the refresh or reload icon from your internet explorer tool bar at the top of the screen, so your screen will reload the latest information. The address of this web site is http://www.geocities.com/sbatteate