by Kristy Enloe
Grulla? Grullo? Blue Dun? Lilac Dun? Silver Dun? Lobo Dun? Olive Dun? Chocolate Dun? Black Buckskin? Slate? and on and on and on...Most of you have heard at least a few of these names when referring to grulla. Here, straight from the major associations, are definitions of the color:
American Quarter Horse Association (AQHA) - Grullo. Body color smoky or mouse-colored (not a mixture of black and white hairs, but each hair is mouse colored); mane and tail black; usually has a dorsal stripe and black on lower legs.
The AQHA pronounces it "grew-yo", and if you register a horse through the AQHA it will come back with a color of G-R-U-L-L-O. However, the AQHA does not have a preference towards pronunciation when speaking, and "grew-ya" is also an acceptable form. Grew-la is not.
American Buckskin Registry Association (ABRA) - Grulla pronounced "grew-ya". Body coat slate colored (bluish gray as the blue heron) from light blue gray to a brownish shade. Points and dun factor markings are black. Dorsal stripe required. The color Grulla is the rarest of all horse body coat colors. The word Grulla is Spanish and translated into English is "crane".
International Buckskin Horse Association (IBHA) - Grulla pronounced "grew-ya". Grulla is an intense color. The body color is described as mouse, blue dove, or slate colored - with dark sepia to black points. Grullas have no white hairs mixed in the body hairs. The hide of a Grulla is comparable to that of a dun and is well pigmented to withstand heat and sunlight. Grulla horses have the dorsal stripe and in most cases have shoulder stripes and leg barring. Grulla is considered one of the most predominant species of the "dun factor". Grulla should not be confused with roan or gray colors.
Genetically speaking, most scientists would agree that a grulla is the same as a black horse - with one exception. Grullas have at least one (heterozygous), and could have two (homozygous), dominant dun-factor allele(s) called the "D" gene. This gene dilutes the coat color to a mousy gray and adds dun factor to the horse's body. The D gene also changes a sorrel to red dun, a palomino to dunalino, and a bay or brown to dun. The "D" gene in homozygous form does not intensify the dilution of the coat like the creme gene. It has not been proven to intensify the amount of dun factor on the horse either. A grulla may also be homozygous for black points.
The genetic mapping of a grulla horse's color is believed by the University of California-Davis to be E?D?CCaarrgg where capital letters are dominant, small letters are recessive, and ? may be either dominant or recessive. Dominant alleles mask recessive alleles, meaning recessive alleles will only be displayed when they are in the homozygous form.
What are these genes?
E The red-factor gene. This gene makes the points (mane, tail, legs) black. If a grulla is EE, it is homozygous for the black gene and it will always throw black points on 100% of its offspring regardless of the other parent's color. Horses can be tested at the University of California-Davis for Homozygous (EE) alleles. This test is commonly referred to as the red-factor test.
D The dun factor gene. A horse can have up to 9 different dun factors, but they will always have at least a dorsal stripe. Other factors include zebra stripes on the front and/or back legs, a transverse stripe over the wither, neck barring (extra stripes/shadowing along the neck), mottling (dark speckles on the forearms and lower hind quarters), tipped ears (actual stripes on ears) and lined ears (black/dark brown along the edge of the ear), Frosting over the mane and tail, a face mask on the bridge of the nose, and cob webbing between the eyes. If a grulla is DD, its offspring will all be dun factored, regardless of the other parent's color.
A This is the Agouti gene. These genes allow/disallow the horse to have a black body if it has at least one "E" gene. If a horse has a dominant agouti gene (A), it will allow the horse to only show black on the points and not the body (aside from dun factor). If no dominant agouti gene is present, the body may be black (Black, grullo, blue roan). Grullas do not have dominant Agouti genes. If an E gene is not present in dominant form, the A gene will be masked in its dominant form.
C This is the Creme gene. A grulla may carry a creme gene, but it is not necessary to have one to be grulla. The dominant form of the creme gene is Ccr and all true buckskins and palominos have a dominant creme gene. A horse that is homozygous for the C gene (CcrCcr) is a cremello or perlino.
R This is the roan gene and its characteristics are only displayed in dominant form. A grulla can have a dominant roan allele, but then, in the AQHA registry, it becomes a blue roan. To be registered as grulla, a dominant roan allele may not be present.
G This is the gray gene, and its characteristics are only displayed in dominant form. A gray can be a "base color" of grulla, but then, in the AQHA registry, it is registered as gray. To be registered as grulla, a dominant gray allele may not be present.
Just How Rare Are Grullas?
Extremely! The following chart is a breakdown of AQHA registered horse for the year 2000. Grulla is easily the rarest color on the chart with only .7 percent being registered as that color. The grulla color numbers are growing slowly. In 1996, .5% of all AQHA horses were registered grulla. Several things have been speculated to have contributed to the percentage rise in registered grullas. Specialized breeders of the color, a strong marketing plan by foundation quarter horse breeders, and more buckskin registries and shows are all believed to have increased awareness and popularity in the color. Spikes in grulla numbers can also be attributed to stallion promotion and successful show stallions of the dun and black colors.
AQHA Color Break-downs - Year 2000
Color Quantity Registered Percentage
News Update: AQHA Color Numbers Are In For 2001...
Grullas continue to be the fastest growing color in the AQHA. While constituting .7% of the total population, they captured over 2% of the total growth. Data compliments of the AQHA, 2002.
Color 2000 Registered Percentage 2001 Registered Percentage
Grullas come in all different shades. The pictures below are examples of some of the variations and there are still more! To increase the size of the picture, just double click your mouse on the picture. Use your "back" button to return!
Grullas come in many shades and can change drastically during the seasons. Grullas are also the hardest coat color to catch on film and pictures can change the actual appearance of the horse. If your attempting to purchase a grulla, or identify a horse as grulla, make sure you know what to look for in the grulla color. A grulla should have a darker head then body (so do blue roans). A grulla should have a uniform mousy color to its back and hip. If the cape over the hip is multi-colored (black and white or black and brown), you may have a roan or a brown. Duns can sometimes be distinguished by a brown or a red toned head that is darker then its body. Gray horses almost always start to gray at the neckline or the top of the forehead and around the eyes. A gray horse will have a gray head and as they age, their head may appear even lighter than the body. It is possible for a gray horse to be born a grulla, but if it turns gray (one of the parents must have been gray for a horse to turn gray), it is recognized by the AQHA as a gray. Roans will start to turn roan in a similar way that grays turn gray. If possible, know the color of the parents. Ask yourself, is it possible for them to have a grulla foal? Gray and roan parents can be tricky because you may not be able to distinguish the base color of the horse. What is always true: One parent must have black points and one parent must have dun factor. Almost any combination of parents can produce a grulla if the above is true. However, the closer the parents are to the grulla color, i.e. grulla, black, or dun, the more likely the horse is to be grulla.
Color Comparison Quick Reference
Color Darker Head Mixed Hair Coat Foals are Born this Color Dun Factor
Present Coat changes after 1 year old At least one parent has dun factor
At least one parent is roan At least 1 parent is gray
All Grullas must have a dorsal stripe - True. Although the description by the AQHA states a dorsal is not required, there are no known grullas that exist without one. What about the "Creme" gene? Well, the creme gene does not affect the black color, or if it does, it is only slightly to produce a "smoky black".
All grays are a good way to produce grulla - False Although gray may appear to look similar to the grulla in color, it does not necessarily produce the grulla color. To know if a gray will be a good grulla producer, one must know the base color - which can be anything from grulla to sorrel. A gray with a grulla base color is more likely to produce a grulla foal. However, statistically at least 50% of the gray horse's offspring will turn gray and should be registered as gray.
If a horse is born grulla it will stay grulla - Most likely. There are some cases where a foal is born grulla and it will turn dun, black, blue roan or gray, but in general, if the foal's parents are not gray or roan, the foal will stay the grulla color. There are rare instances when a foal will be born the same shade as a normal black foal and it will shed off the foal hair to become grulla. These foals are always born with noticeable dun factor, especially a deep black dorsal stripe and they grow up to be extremely dark grullas. There are also rare cases where foals are born a "questionable" dun color and will shed foal hair to a normal grulla color.
A grulla horse must have both a Dun-Factor (D) gene and a Creme (Ccr) gene - False, but highly debated. A grulla may have both genes, but the genes are inherited separately. Some researchers believe the existence of the creme gene will lighten the overall coat, but the University of California at Davis disagrees. They plainly state "The creme gene will not affect the black body color".
Silver Horses are Double Dilutes - Maybe. What is a silver horse? Everyone has a different definition. The University of California at Davis believes the dun factor gene does not intensify in the homozygous form. There are horses in existence that are known to be heterozygous dilutes that are clearly the same color as other homozygous dilutes.
Photos provided by
Eunice Pitts - Arrow Chip Acres ( http://www.horsecity.com/ARROWCHIP/ )
Enloe Quarter Horses ( http://www.enloequarterhorses.com )
Research Assistance: Eunice Pitts, Theresa Ann Warden, University of California-Davis.
Additional web sites with genetics information:
The genetics behind the hide: http://www.geocities.com/Baja/Outback/2936/
University of California-Davis: http://www.vgl.ucdavis.edu/~lvmillon/
The Buckskin and Foundation Quarter Horse Magazine http://www.bhfqh.com/BH-FQH/
D. Phillip Sponenberg and Bonnie V. Beaver. 1983. Horse Color-A complete guide to horse coat colors.
Dr. Ben K. Green. 1974. The Color of Horses - The Scientific and Authoritative Identification of the Color of the Horse. pg 110-111.
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