October 24, 2007
DNA Testing in Equines
By Michal Prochazka, MD, Founder & Director, Pet DNA Services of Az, Tempe, Arizona (www.petdnaservicesaz.com). PDSAz is offering tests in horses (colors, spotting, selected heritable disorders), and bird sexing.
Over the last couple of decades, advances in molecular genetics made it possible for DNA testing to become the method of choice for a variety of applications, ranging from human medicine and forensics to our hobbies involving pets and domestic animals. In this article, I have attempted to present a simple overview of the use of DNA tests in horses.
When talking about genetics and DNA testing, one cannot avoid the use of specialized vocabulary, which I will explain briefly, before discussing the applications of this technology in our equine friends.
Practically every cell in the body contains DNA, which is the “blueprint” code of instructions determining the appearance and function of an organism. The DNA is arranged in rod-like structures called chromosomes located in the nucleus. Chromosomal segments carrying discrete codes for specific traits and functions are called genes, and with the exception of the sex chromosomes all of the other chromosomes (and genes) in animals and humans are present in pairs, with each parent contributing one half of the material. In general, both copies of a gene are identical, but some carry discrete differences (mutations, variants), some of which can result in visible differences – for example a variation in the coat color. Such alternate variant forms of the same gene are called alleles, and an individual is referred to as a homozygote when both alleles in a pair are the same, whereas an individual carrying two different alleles of the same gene is called a heterozygote.
Depending on their biological properties, two alleles at any gene can interact in different ways. An allele is dominant when in a heterozygote carrier only this allele will show an effect. Furthermore, its effect is the same, regardless whether the individual has one or two copies of such allele (= is either a heterozygote or a homozygote for it). Conversely, an allele which is masked by its dominant counterpart is called recessive, and the effect can only be visible in a homozygote. A special situation is that of incomplete dominance, when one allele shows a certain effect in a heterozygote, but the expression is more pronounced when the carrier is a homozygote (a typical example in horses is the Cream Dilution).
The combination of alleles at one or more genes is referred to as genotype, while the visible manifestation of their effects is called phenotype. Due to interactions between genes and alleles, a phenotype usually does not provide full information about the underlying genotype.
The molecular differences between DNA alleles are tested with the use of sophisticated laboratory technology. The majority of routine laboratory DNA tests involve the Polymerase Chain Reaction (PCR), which allows for selective amplification of a DNA segment of interest in a test tube, thus making it accessible for further analysis to find out what alleles an individual may carry within this particular piece. As practically all tissues and cells from the same individual contain identical DNA, one can use a variety of sources for the testing. The material typically used in horses and other equines is pulled mane or tail hair, or blood. The accuracy of DNA testing is not dependent on age, and one can obtain reliable results already in newborn foals.
DNA testing in horses can be used for various purposes. One of the common applications, familiar to owners of registered horses is DNA “profiling”. In principle this technology is the same as DNA “fingerprinting” used in human forensics and paternity testing, which utilizes highly informative sets of genetic markers to differentiate with a great precision between individuals. Such tests are used very accurately to verify parentage, and identity of animals. DNA testing is now a mandatory requirement for registration by several US registries, with the main purpose of preserving the integrity of horse breeds.
Another important application is testing for the presence of mutations causing heritable disorders. Some examples include HYPP (Hyperkalemic Periodic Paralysis) and HERDA (Hereditary Regional Dermal Aplasia) which are carried in some lines of Quarter horses and related breeds, or SCID (Severe Combined Immunodeficiency) found in Arabians. These tests allow for an early and reliable identification of carriers, thus providing the option to either exclude such horses from breeding, or to avoid mating of two carriers to prevent production of affected offspring.
Further application of DNA testing became possible with the identification of some of the genes involved in coat color differences, or development of spotting patterns. It has been estimated that there are at least 15 separate genes contributing to different colors and white patterns in horses, and several of them have been already identified and reported in scientific literature.
To make the best use of DNA testing for color, one first needs to understand the concept of base colors. Like most animals, the horse has two pigments - black (eumelanin), and red (pheomelanin). The difference between the production of red alone, and red plus black together is controlled by alleles at the Extension gene. The dominant “E” allele determines the production of the black pigment in addition to red, whereas the recessive “e” allele (also called the Red Factor) permits the expression of red only. Consequently, e/e homozygotes have only red pigmented hair (chestnut, sorrel), while horses heterozygous or homozygous for the dominant allele (E/e or E/E) produce both red and black pigment. In the presence of the E allele, the body distribution of black pigmented hair is further controlled by alleles of the Agouti gene. A horse carrying the dominant “A” allele (genotypically either A/a or A/A) will have the black hair restricted to the points (mane, tail, legs) and will be phenotypically a bay. In contrast, the recessive allele “a” does not restrict the black hair, and a homozygote (a/a) will have this color distributed evenly and will be phenotypically black. Although not formally proven yet, there is considerable evidence for a third Agouti allele (called At) which appears to be responsible for the seal brown color in E/E or E/e horses. The current Agouti test (specific for “a”) cannot differentiate between the bay A allele and At, and we at PDSAz are conducting a study to further explore the genetic basis of this color.
In principle there are two base colors in horses: black, and red. However, for practical purposes we usually recognize three base colors (bay, black, and red), which are produced by the interactions of the known alleles at the Extension gene and Agouti (I am purposely leaving out the brown color, as it has not been scientifically proven yet). Depending on the alleles in the parents, two horses of the same color (= phenotypically identical) can differ in their genotypes at the involved genes: there are four different possible genotypes in a bay horse (E/E A/A; E/E A/a; E/e A/A; E/e A/a ), three in a chestnut (e/e A/A; e/e A/a; e/e a/a), an two possibilities in a black horse (E/E a/a; E/e a/a). Although the Agouti has no obvious effect in red-based (e/e) horses, it is important to keep in mind that such horses always carry two Agouti alleles, which can become relevant if they are crossed with a bay or black partner. Accurate knowledge of these genotypes is very helpful to predict which colors any given horse can (or cannot) produce, and at what frequency.
The variety of colors and patterns which occur in horses are produced by interactions of one of the base colors with additional modifying genes and alleles. Most of them are dominant and include several dilution genes (such as Cream, Dun, Silver, Champagne, Pearl), or genes determining the presence of white hair, which can be distributed diffusely throughout the coat (Grey, Roan), or as distinctive spots (Tobiano, Overo, Sabino, Appaloosa). As these colors and patterns are caused by alleles in separate genes, combinations of two or more of them can occur in the same horse.
Regarding white spotting, I believe that it is worth mentioning the most consequential mutation which is the Lethal White Overo (LWO) causing the Lethal White Foal Syndrome in LWO/LWO homozygotes. In carriers (= heterozygotes carrying one LWO allele), this mutation if frequently associated with the frame overo pattern, but the expression can vary widely, ranging from a loud overo to a solid colored individual. LWO mutation is found across various breeds - not just Paints and Pintos. If there is the slightest chance of a horse carrying LWO, it is a good practice to routinely test for LWO, to avoid unintentional mating of two carriers, which would have a 25% calculated risk of producing an affected white LWO/LWO homozygote.
While the primary focus of horse breeders is the improvement of conformation and performance, the diversity of coat colors and spotting patterns can also play an important role. From the described facts it is clear that DNA testing combined with the understanding of basic genetic rules can enable breeders to make informed decisions about which horses to mate to maximize the production of desired colors and patterns. Furthermore, quite often is DNA testing critical to determine the true color of a horse, thus facilitating a correct registration.
Although the focus of this article is genetic testing in horses, color and spot breeding is also becoming popular in donkeys. Our laboratory is currently involved in a study with the goal to develop DNA tests for donkeys in the foreseeable future.
(- A few questions to clarify things:)
1. At the moment, can DNA testing determine a donkey breed? Or just parentage?
DNA testing in donkeys or horses can determine parentage, but not breed.
2. Can DNA testing determine a horse breed, or again, just parentage?
Please see my answer to Question #1.
3. A bit off topic, can DNA testing determine a dog's breed?
Yes. There is a company in California which can test for dog breeds (http://www.mmigenomics.com/products2a.html)
4. What does the word "Agouti" mean?
Agouti is a rodent living in South America, which has a typical hair color pattern that is also found in many other animals (mice, rats, rabbits etc). The hair has dark and light banding, which is controlled by a gene that has been named Agouti. This gene modifies where the black pigment shows up. In the mice, for example, it gets switched on/off during hair growth, and therefore the so called grey (wild-type) mice have a part of the hair that contains the yellow/brown pigment (Agouti is on), which alternates with black (Agouti off).
This gene is found in all mammals. There are two variants of this same gene in horses (A, and a) which are responsible for the difference between bay (black hair only in the mane, tail, and legs), and solid black color.
BTW - It is my understanding that some of the gene names we are using in pets and life stock were taken originally after the gene names in laboratory mice. These include for example Agouti, or Extension (black and red factor).
5. A few of our reader's have had DNA testing done to determine the parentage of foals. How accurate is the DNA testing?
Parentage testing is very accurate in horses (although there could be differences between different labs). Because donkeys' DNA is very similar to horse, the horse parentage tests will also work in donkeys, but I am not aware of any info about how accurate it may be.
6. Have you found that the Lethal White gene in horses also occurs in donkeys?
We have not looked specifically at that yet.
7. Eventually, will we be able to color test our donkeys to ensure the correct color on registration?
This is the main goal of our study, to develop tests to correctly define colors in donkeys, and also predict what colors can individual donkeys produce in their offspring. We are conducting the study in collaboration with Leah Patton from ADMS.
8. What are some of the differences so far that you've encountered between horse DNA for color and donkey DNA for color?
Our study started just recently, and we do not have enough data yet to make any reliable statements about this.
9. I have been told in the past that all donkeys have a cross and dun stripe, although it doesn't show on all donkeys, do you know if that is true? Or will that be one of the questions your researching now?
Leah Patton and I have been talking about this. Right now, we are focusing on genes which determine the base colors (brown, black, and sorrel/red), Depending on how the study progresses and if we can get some funding, we would consider in the future looking into the genetics of donkey markings (cross vs no cross; light points vs no light points).
Michal Prochazka, MD
Founder & Director
Pet DNA Services of Az
(Equine testing; Avian sexing)
If anyone wants to help with color research on donkeys:
ADMS does not provide any funding for this project. Any donations should say that it's for the donkey color research, and should be made to Pet DNA Services of Az, and mailed to PO Box 7809, Chandler, AZ 85246.
Anatomical Differences in Donkeys
We all know the differences between donkeys and horses by sight. But, the differences that are easily seen, like ears, are not the only differences to be aware of.
Donkeys have a short, upright mane, usually no forelock and a broomstick kind of tail. Donkeys are not just a “poor man’s” horse. A donkey reacts totally differently than a horse, has a different outlook on life, and different nutritional requirements. For those of us who are familiar with donkeys, we understand that they are a smart, affectionate, unique equine, well worthy of their own respect and appreciation. Obviously, some training methods commonly used for horses won’t work very well for donkeys. That will be another article. For now, let’s just cover some of the major anatomical differences we have in our donkeys.
One of the biggest concerns with donkeys is castration. A normal castration of a horse, the vet clamps the blood vessels until the bleeding stops. Then, he allows the incision site to stay open and drain. Unfortunately, donkeys seem to bleed more than horses, and some can be heavy bleeders. It is recommended that the vet use ligation (this is when the vet places a stitch in the blood vessel to help stop bleeding) in donkeys when castrating. If your vet isn’t aware of the differences in donkeys, a frank discussion with him/her before scheduling the surgery is in order. There are some places that you can find reference materials on the internet that you can print copies of and give to your vet (a few reference sites will be listed at the end of this article). Occasionally, a vet will not take what your saying to heart, our advice to this is to find a vet who will. There have been way too many close calls to leave it up to chance, and a few deaths have been reported.
Another common difference is gestation time. Gestation for horses is generally about 11 months. For donkeys, gestation is usually about 12 months, but anything from 11 ½ to 13 months is normal. Live, healthy twins are also more common in donkeys than horses, by about 100 times. Care still must be taken, and many breeders will have jennets known to have twins ultra sounded early in their pregnancy, and one of the twins pinched off, to give mom and the other twin a better chance of surviving.
Donkeys also have a longer life span than horses, and can live easily in excess of 45 years. Horses average lifespan is 25-30 years.
To find the jugular vein in a donkey is a bit more difficult than in a horse. Blood used for tests such as coggins, or drugs that need to be administered intravenously, such as tranquilizers, are usually drawn or given through the jugular vein. The muscle that covers this area in donkeys is much thicker, and usually hides the middle third of the jugular vein. The jugular farrow in donkeys is obscured by this muscling in comparison to horses. Most vets will use the upper one third or lower one third of the jugular farrow in a donkey.
The nasolacrimal duct is found in a different location compared to horses. In a donkey, the duct is found on the flare of the nostril. In a horse, this duct is found on the floor of the nostril.
Chromosome differences are usually pretty well known. A donkey has 62 chromosomes and horses have 64. For this reason, almost all mules are sterile, since they end up with 63 chromosomes.
In donkeys, the pelvis tips down more vertically than in horses. This is especially helpful to know when a vet is conducting a pelvic exam, or if dystocia occurs.
Also, a jennets cervix is longer and narrower than that of a mare. There is also a large protrusion from the cervix into the vagina. And, dorsal and ventral folds in the vaginal passage that can hinder passage to the cervix.
Male donkeys, or jacks, also have some notable differences. Some jacks have teats on their sheath. Jacks are also notably larger in reproductive areas than horses.
Donkeys do not have chestnuts on their hind legs. They do have ergots on their front legs, which are mainly just a flat pad.
Donkeys hooves are also smaller than horses, and tend to be boxier and more upright.
One primary difference between donkeys and horses is their larynx. Vocal folds and laryngeal saccules were found to be different then horses and account for the braying sound that a donkey makes. One other thing to be aware of when a vet is tubing a donkey, the nasal passage is very narrow, and there is also a recess between the openings of the guttural pouches. For this reason, when passing a tube, a smaller diameter tube is better to be used. Donkeys are known for excessive bleeding during this procedure, and a smaller tube may help the bleeding problem.
There are many other differences between horses and donkeys, such as vertebrae, that are too lengthy and confusing to go into for this article. Just be aware that if the vet needs to give an anesthesia shot in the spine for any reason, it differs from horses and the vet should be aware of this fact.
Of course, there are many other differences besides the physical ones mentioned here. Donkeys are known to be stoic, what many call stubborn is just self preservation, and donkey behavior must be understood to manage them effectively. Subtle differences in behavior or attitude may indicate severe problems.
It’s good to know your animals, it helps with the vet, the farrier, and anyone who may come into contact with them. If you treat a donkey like a horse, you will be disappointed with the results.
The Definitive Donkey- A Textbook on the Modern Ass. Hutchins, Betsy and Paul. Hee Haw Book Service, 1999.
The Professional Handbook of the Donkey. Svendsen, Elisabeth D.. Whittet Books, 1997.
Trail Riding Etiquette for Donkey Riders
By Marna Kazmaier
Belle Fourche, SD
I love organized equine trail rides. The more folks that come on each one, the merrier. My husband, Deron and I have spent many weekends in WI at these well organized and good clean fun events. Many, if not almost all, had live bands on Saturday night, campfire dinners, campfire
breakfasts and good ole campfire stories as well as campfire games.
Deron and I also have been on many group rides. This is where a friend calls up several people and says, come on over on this day, at this time and bring your horses, we will ride a couple hours before dinner.
One thing we found was that many equine riding folks do not know anything about trail etiquette. You would think that common sense would rule....but no. Just like so many spoiled children exist in public restaurant today....rude folks are on horse back and at these organized and unorganized events.
So how do you deal with this? You must keep the humor in it all. You must not allow other peoples rudeness, albeit some of them are just stupid
One thing you can do is nicely say "I am not sure if your know this or not, but you really should keep at least a horses length between riders. Pretend that there is an imaginary horse between us." or "Please don't run up on people riding horses while on a trail ride, it can excite the younger horses. Don't forget there are inexperienced riders here. I would hate to see you face a lawsuit over not abiding by trail etiquette." Or another thing you can nicely say is "Please stay on the trail, we don't own this property and we sure hope to be invited back for this ride again next year. One good way to ruin that is to get off the trail and offend the land owner." When you say things like these it puts the blame, if you will, on a third party, so of course, well, most of the time, the other rider
Sometimes you just have to grin and bear the other people's rudeness and just "talk about them" back at camp. You know, "constructive criticism". Sometimes, gossiping, oh I mean, "talking it out" with other understanding riders, will make you feel better and life will go on. Again, remember it may be there first organized ride.
If this is your first organized ride you may want to buy a nice set up saddle bags. You might want to use these, lightly packed, at home on the trails there before filling the up and taking off out on a trail with many other riders. Your animal may be a bit overwhelmed with the ride, the more you can get your mount used to before the ride the better. A Cantle or Horn Bag may be all you need, but like I said, try them at home first. Just remember, an organized ride with many riders is not the place to try new tack out.
What to put in these bags? Always take your rain gear. Yes. Even if rain is not expected, take it anyway. You might want to put a hat and gloves in your bag in the winter, spring and summer months. It can get pretty chilly in the woods on an early morning ride. A small first aid kit that you have packed so that it does not rattle inside while riding. A lead rope and halter if not already on your horses face. Most folks do, while trail riding, leave a halter on under their equine's bridles. Carry a pocket knife and some cash in your pockets as well as your truck keys. Many rides have Half Way Points and at them sell food and or drinks. You may want to carry a cold drink, not carbonated, in your saddle bags. Carry anything else you can think of you might need while out on the trail (think monthly ladies).
Remember when packing for an organized ride you are mixing equine riding and camping, make lists, mark things off the list as you load them. Start your list a week before the event and add to it as you think of things you may want to take....unlike backpacking, you are not camping light when you go with a horse trailer and truck.
If you normally high tie your animals also pack wire and poles for a small pen. There may not be any trees where you are going, high tying may not be allowed or all the trees may be taken by other riders. Be prepared for any event like these.
Bring and wear clothes in layers. Always pack a jacket, even in the summer months. Don't forget to bring your normal riding clothes. While you will want to dress nice, you still need to be safe and comfortable. Keep in mind on several organized rides the press will come and take pictures for the paper....sometimes the TV news teams will even come and film. Dress as you would like for the world to see you.If you sleep in a tent set the tent up next to your vehicle. If horses get loose and run during the night staying close to vehicles is safer. You might not get trampled, if you are close to something they can see, like your rig. Some folks clean out the back of their trailers, throw down a tarp, then set up their tent in the trailer. It is a safe, dry and private place to sleep. When you build your campfire remember it's a campfire, not a bomb fire, keep it small. It is best to make a rock fire ring around where you will be building the fire. Put all fires out before
leaving for the trail or going to bed.
Lock your rig when you leave for the trail. Put all valuables away in your truck or trailer before leaving. Most organized rides are advertised.....don't you just hate that thieves seek out easy targets like this?
If you don't know......some of the Organized Rides unwritten rules are:
*Leave room for folks to tack up and move their horses around between rigs, trucks/trailers.
*Don't "pile up" at the beginning of the ride while lining up at the starting area. It may take some time to get started, some organizers mark and count horses as they leave for the trail. Most mark with a small colorful piece of yarn knotted on the bridle.
*No running children though camp (that also goes for adults and is tailored for drunk adults).
*Set up a small pen for your horses for the week end....this is not their grazing home, just a week end get away. A small pen.
*Don't approach other peoples animals without asking the owner.
*If your animal has EVER kicked or threatened to kick tie a red ribbon on/in it's tail. Don't cheat on this one.
*Stay on the marked trail.
*Don't run your horses out on the trail unless it is a running/cantering area. Never run up on other horses on the trail.
*Be patient when crossing water. Don't spook, slap or push other people's hesitant horses.
*Quiet after 11 pm.
*Support the local club that put the ride on they only charged you about $2 per equine to get in. Buy their raffle tickets.
*Children are welcome IF they behave and are going with you on the rides. None left in camp during the rides. Keep them with you for the entire week end (or length of the event)
*Dogs, ALL dogs, stay at camp for the day's ride and with you or chained out/crated/contained at all other times.
*If the Event Host hands you any papers READ THEM.
Of course on some rides you would want to write up and hand out rules for the stupid people, they might say:
**Don't steal stuff. A saddle, grill or other items setting out DO belong to someone and YES!! they do want to keep them.
**Leave the rider's horses/animals alone. No, you may not ride the Stallion.
**Keep your &@#! brats, I mean children, with you and under control.
**SHUT UP, it is 1:30 am.
**No one here thinks you are as cute as you think you are when you are drunk.
**Don't lean on, especially while drunk, other people's horses, or other people.
**No, we do not want to hear your type of music blaring all over the entire camp.
**Don't flirt mercilessly with other people's spouses.
**Your dog may run loose at home, even though your neighbors don't like it, but they can not here.
Now luckily the stupid people are far and few between at these events. Most of the trail rides I have been on there was no trouble at all. But I have seen an awful lot of painted ponies.....war paint, grease paint. It happens during the night and nobody knew who might have done this. My
question is? Who raised these people and how have they survived this long? You know? No one has...... well? Offed them out in the woods? They have survived working around equine being as stupid as they act around equine? Why have they not fallen off in some of their stupid equine acts!!?? But you have to laugh. You must keep your humor....after all, you are riding a donkey. Those of us riding donkeys have good humor. We look at life a bit differently.
Donkey owners, lovers, riders are for the most part, a fun, quick witted bunch . I know that cause I have met many. I have been so taken aback at how "half full thinking" donkey owners are. They not only care about animals, all animals, but also people. They welcome newcomers to their hobby or what they call life style and they do so with open arms.
So when it comes to idiots on the trail.....most donkey riders are ready. Ready for the same question they are asked over and over and over......YES!! It is a donkey. Yes, they really get this big. No, it is not a mule. No, I did not loose my horse. No, I did not off a prospector. No, I am not from Mexico. Donkey people are so ready for thequestions that there are even T-Shirts that read YES IT IS A DONKEY.
But what about the idiots that ask the really rude questions....what are some "come backs" for them. Yes, they do hear better with the bigger ears Goldilocks. No, the guy illegally come across the boarder did not feel a thing. It may not outrun your horse, but I am sure it can out think it. No, I don't like riding donkeys, but since I own six and they are less spooky and more sure footed then horses, so I thought, "what the heck". Yes, it's name is Eeyore, isn't that the only name you can give a donkey? See Shriek? I was in it!!
But, then, we must remember that many folks are truly asking because they do not know. They might really want to own a donkey and just don't know anything about them. I know I was/am drawn to them when I saw them at rides. I don't think I asked stupid questions....but who knows.
What you should bring to an organized ride:
*your mount, horses or donkeys or mules or just say equine
*proof of current coggins testing, usually a copy of the papers for the gates person to keep (this is how they keep count)
*your saddles and saddle pads as well as your bridles or equivalent
*saddle bags, cantle and or horn bags
*pen or high tie equipment and don't forget the battery if it is an electric fence
*halters and lead ropes for each animal you take
*an extra lead rope
*grooming supplies for both animals and people
*food for your animals
*food for yourself
*drinks for yourself and family or friends with you
*extra food, people will drift and land at your campsite....and you will be glad they did
*clothes and if there will be a dance, nice clothes
*anything you have equine related or any equine you might have for sale, and for sale signs
*water buckets and water if it is not offered in the advertisement for the ride
*a way to wash your cooking utensils
*can opener if applicable
*plates, forks, ext for eating
*treats for your animals
*trail treats for yourself, sometimes rides can and do last all day
*cash/money - you might be surprised what you may need it for
*everything you need for sleeping; sleeping bag, pad, pillow, clothes, anything you need for sleeping
*an extra blanket
*flashlight and batteries, that is *and extra batteries*
*extra flashlights, they break or don't work when you need them the most
*matches for your campfire and of course wood for your campfire
*yes, wood for your campfire, there may not be any where you are going
*coffee/tea/hot cocoa and a way to fix it
*back up food for those who have never prepared food over a campfire before
*apple picker (pooper scouper) some rides require picking up areas
*first aid kit for both humans and animals
*guitar, harmonica or other musical instrument if you play well
*toilet paper - wet wipes
**MOST OF ALL, YOUR GOOD HUMOR, AN EXTRA DOSE FOR GOOD MEASURE!!
Jon & Roberta
On the Donkey page: Colors in the Donkey
By Leah Patton
Office Manager, ADMS
Colors in the donkey range from the gray shades of gray-dun to brown, a rare bay (though not as red-toned as in horses) , black, light-faced roan (both red and gray), variants of sorrel (Registry term - RED), the blue-eyed Ivory (also called cream or white-phase), Frosted/spotted White, and a unique Spotted pattern. True horse pinto, horse aging gray, horse appaloosa, palomino and buckskin do not occur in the donkey.
The more unusual colors are the Dappled Roan, where the face and legs are light and the body is marked with "reverse" dapples (dark spots on a light background, as opposed to the horse dapple where the dapples themselves are light on dark), frosted gray (with light faces and legs and some white hairs in the coat) the pink-skinned, blue-eyed Ivory white, and the frosted spotted white. The frosted spotted is an apparent combination of a graying or roan with the spotted pattern, and can throw either more FSW, spotted, or frosty roan colts. The animals are best defined as a spotted animal where the skin is spotted but the color does not necessarily show through on the coat (it has roaned or "grayed"; out) . Frosted spotted white (FSW) can be identified from Ivory white by checking the skin around the eyes and muzzle. Ivory (creams) will have blue eyes and true pink skin, while FSW will have dark eyes, dark "eyeliner" and dark spotting on the skin.
Another unusual variant of the spotting line is the "tyger spot" pattern. These donkeys vary from the typical large spots over the ears, eyes, and topline. The body will be covered with small round spots resembling the appaloosa type.
Registry color terms
Very Dark Brown
White * (FSW or BEW)
+ Spotted (ie, Gray and white spotted, Brown and white Spotted, Red/Gray and white spotted).
Note - no Mammoth donkey are ever recorded as having been Blue Eyed White (Ivory).
Russet is a descriptive term only, until such time that there is a genetic determination of the workings of russet. They are listed as Red (Frosty roan, black trim, russet pattern) or Brown (red tones in coat, frosty roan, black trim, russet pattern).