Whence Come the Color Dun?

Altamiro/October2007 (photo: Leslie Town)

I know very little about the genetics of equine hair coat patterns and honestly find genetics to be way over my head in whatever capacity they are presented. This cerebral deficiency is likely a combination of my being an artist and being rather lazy-minded unless something really "speaks" to me, (or I could be a bit less self-deprecating and say that I'm not lazy-minded, rather prudently filtering out non-essentials). Let's just say science and mathematics don't connect the right neurons in my brain to spark the inspiration that fuels understanding.

Finding myself now part of a project to preserve the genetic treasure of an ancestral equine form as represented in the Portuguese Sorraia and in certain North American Mustang horses, I have had to acquire a rudimentary comprehension of the primitive color that is an integral part of these horses' phenotype.

The half Sorraia half mustang foals, Interessado, Fada and Animado/autumn 2008

As I've shared in various articles, the Sorraia horse is a remnant specimen of the indigenous wild equine of the Iberian Peninsula. His coat color is always a variation of dun, with hues of creamy yellow, tan and buff or a version of dun referred to as "grulla" with ranges of soft greys of blue, silver and lilac or deep, sepia-toned charcoal. It's a color that alters with the seasons and with the play of light, but whatever variation of dun a horse has, it will always have a dorsal stripe and black lower legs. Other primitive elements are often present as well, such as a bi-colored mane and tail (lighter outer hairs fringing the interior black mane), shoulder and leg barring and two-toned ears. Some dun-colored horses, like the Norwegian Fjord, have lighter colored muzzles (mealy mouth) and lighter under-bodies. Sorraia horses, by contrast have darkened, "smutty" muzzles and faces and uniformly colored under-bodies.

Animado with his dam Bella/Summer 2008

Dun is considered a dilution of either the base color of chestnut, bay or black. The dun coloring represented in the Sorraia is a dilution of bay base color or black base color and is often referred to as "yellow dun" or "black dun" respectively. Black duns are also referred to as "mouse dun" or "mouse grey", to differentiate it from the true grey found in other breeds. The Portuguese word for yellow dun is "baio" and for mouse dun is "rato". More commonly, mouse dun horses are called "grulla" (grullo/grulla is a Spanish word for a blue grey crane). Some medieval Iberian hunting texts described the wild equine of the area as horses which were "rat" colored with dark faces. Many versions of dun horses are represented in cave paintings in parts of Europe.

Purebred Sorraia stallion, Altamiro/October 2007 (photo: Leslie Town)

The Veterinary Genetics Laboratory at the University of California, Davis has been doing extensive research into color genetics and offers a variety of tests for horses, one of which is to determine "dun zygosity". The link for this test is here:
http://www.vgl.ucdavis.edu/services/dunhorse.php

Curiously, this test is not yet being offered for Iberian horses and the test itself is limited in scope as the specific mutation that causes the dun dilution has not yet been identified. At best it can discern particular DNA markers associated with the dun color and how many copies a horse possesses. Using these markers coupled with photo images of the horse being tested and a three generation pedigree, the test can give a pretty good determination of whether the dun gene is present or not.

Bella and Belina/October 2007 (photo: Leslie Town)

Quite some time ago, it was suggested to me that I send hair samples from Altamiro to assist in this research of the dun gene. When I finally got around to connecting with Dr. Cecilia Penedo who heads the research team, Altamiro had sired three foals out of select mustang mares with varying degrees of the Sorraia phenotype. Dr. Penedo requested I send along samples from Animado, Fada and Interessado as well.

First, they completed a general "horse coat color" test. Altamiro and his three foals all came back with the same results: their base color is black with no other color dilutions except for dun.

The half Sorraia filly, Fada/Autumn 2008 ( photo: Carolyn Haggart)

Next up, the "dun zygosity" test. I did not get any report back on Altamiro (have inquired but received no reply so far). One came back for Animado which lists him as D/D and says, "Horse is likely to be homozygous for the Dun gene. All offspring should be Dun dilute."

Later, I received a note from Becky Evans relaying that Fada and Interessado's samples were giving "unusual results" to the tests and asked if I would send along hair samples from their dams Belina and Ciente.

Altamiro (back) with Belina and Ciente/Spring 2008

After running tests on Belina and Ciente, the following "dun zygosity" results were mailed to me.

Interessado: Inconclusive 1 --Dun zygosity cannot be determined for this case.

Fada: Inconclusive 1 --Dun zygosity cannot be determined for this case.

Ciente: D/N --Horse has one copy of the Dun gene. Horse will transmit Dun gene to 50% of the offspring.

Belina: D/N --Horse has one copy of the Dun gene. Horse will transmit Dun gene to 50% of the offspring.

When I asked Becky what this all meant she relayed the following: "The results for Altamiro and his offspring were not clear cut for dun. Altamiro has an unusual combination of markers that we have not previously seen for dun. Fada and Interessado did not inherit dun from their dams, and both are unusually dark for horses that are dun dilute."

Interessdao and Fada/Autumn 2008

So, there it is, whatever it is! I'm still pressing for greater clarification and have been researching Altamiro's pedigree (which goes all the way back to the foundation stock d'Andrade gathered saving these indigenous wild horses from extinction) as well as those of Belina and Ciente.

Obviously, there is much more to be learned about the genetics involved in dun coloring. So far it would seem that Altamiro and his foals have shown that its a very complicated process, and testing their hair samples has not made things any clearer for the researchers--at least not yet.

The author with Ciente and Interessado/Autumn 2008 (photo: Carolyn Haggart)

Images From Spring on the Last Day of November

Left to right: Altamiro, Belina, Fada, Bella and Animado

For the past two days I've been sorting through my iPhoto library looking for suitable images to send along with hair root samples I've collected for the Veterinary Genetics Laboratory of the University of California, Davis. UCDavis has been researching equine hair coat colors and has not yet been able to identify the specific mutation responsible for the dun color. The scientists as UCDavis are looking at Iberian breeds to help unravel this puzzle, and have requested samples from Altamiro, Animado, Fada and Interessado to assist them in their efforts.

Between the early winter weather (with snow falling just about every day--a barn sure would be handy at times!) and my desire to make the hair plucking experience as non-invasive as possible, it has taken me several weeks to acquire the 20-30 hairs per horse that the researchers are looking for. At first, my task was compounded as I tried to select hair from manes and tails with a pair of tweezers. This worked well enough on Altamiro's mature hair, but not so easy a thing for the finer and more slippery foal hair. I found that if I simply gathered about five or ten hairs together while I was itching the tail dock, I could easily tug out the selected amount with my fingers with no irritation to my wee equine companion. Fada, especially seemed to enjoy these rather vigorous itches and it was very easy to get hair samples from her as she would just lean into the feel, arch her neck and wriggle her lip. The boys, though, while enjoying getting their tails itched, also wanted to nibble on my clothes or shoulder basket, making it a little trickier to get the job done.

At any rate, I came across some photos which I don't believe I have yet shared in this blog. With it very wintery outside, I thought it might be nice to smell the green of spring through the viewing of these photos.

This is Fada's first day of life and she is exploring her new world with the careful protection of first time mother, Belina. When I viewed this photo again the other day, I had tears in my eyes it seemed so tender a scene, with Belina looking especially beautiful.

Belina and Fada

This next one shows Belina about three weeks before delivering Fada. She is harassing Altamiro about some thing as they and Bella wander through the Hidden Meadow.

Belina, Altamiro and Bella

This next one shows Ciente looking at the camera with Belina and Altamiro in the back, with Belina still looking a bit peeved about something.

Altamiro, Belina and Ciente

Here is another photo from Fada's first day. I had forgotten just how tiny she was then!

Belina, Fada and Altamiro

A bit later in the season, we have a tranquil moment with Fada laying down, Belina dozing while standing and Animado (all shed out and looking sleek!) hanging out with them in a field of wildflowers.Fada, Belina and Animado

Here's one with Altamiro and Ciente grazing together.

Altamiro and Ciente

This one is probably from summer, but I like this matched pose and the view we get of the toplines of Animado and Bella.Animado and Bella

It's difficult to believe that we've gone through the month of November already. When I look at these photos from earlier in the year, it doesn't seem possible so much time has passed. And when I look out the window now and see all our snow, I think it will be a long, long time before I see spring green again!