The IMPORTANT INFORMATION REGARDING THE SILVER DAPPLE GENE

PLEASE READ THE FOLLOWING WHEN CONSIDERING BREEDING FOR SILVER DAPPLE:

Silver dapple color had always intrigued me, though not until I owned, stood and
researched it did I find out how special this particular color is. It is probably the most
exotic and unique color in the horse world. I had bred AQHA grullas for 6 years as I
was becoming addicted to the gypsy. I was very excited by the dilute colors,
however, the silver dapple Z gene, is in its own right a diffe
rent genetic world.
I have had personal discussions with Dr Phillip Sponenberg, a foremost author of 3
volumes of Equine Genetics. He is a scholar and a world of information for me that I
deeply appreciate so much what I have learned from him. We met when he emailed
me asking if he could use 2 of my horses in his book Vol. 3 Equine Genetics, as
representing the silver dapple. He used St Clarins and a tobiano spotting pattern, Cici’s Dottie Lady.
As we spoke, I learned detail about the Z gene. Being a curious person who wants to
do right by my breeding program, I learned that though beautiful a color, there is a
danger in which indiscriminant breeding can provoke into a time bomb. What is there
which could cause such a dramatic statement?


“SILVER DAPPLE OCULAR CHANGES IN HOMOZYGOTES

 <AKA> Z/Z FOR SILVER ALLELE”

This is taken from Dr. Phillip Sponnenberg’s 2nd edition of his book ‘Equine Color
Genetics’ 2nd edition’-published in 2003 from the Iowa State Press.
“Re. silver dapple ocular effects. Ocular changes are consistently associated with
colors of this grouping many breeds in which this allele occur, so it is safe to assume
that the ocular changes are indeed part of this allele. Detailed studies have yet to be
done, BUT the anecdotal evidence suggests that when heterozygotes are minimally
affected and vision is normal or nearly so. Homozygotes have profoundly affected
eyes, and some are affected to the point where vision is NOT normal. A simple
breeding strategy to avoid producing visually deficient horses of these colors is to
mate SILVER to NONSILVERS. This can be tricky in some breeds in which this allele
is common, because CHESTNUT and SORREL horses will not express the allele, but
can carry it. They could pass it on to a foal and could therefore be responsible for
producing homozygotes. In breeds in which this allele is common, it is safest to mate
chestnut, sorrel or colors derived from these to bay, brown or black mates free of the
silver dapple allele. This strategy assures that the production of homozygotes is avoided.”
“I also have spoken to Saskatchewan, Veterinary University’s Bruce Grahn, DVM,
Dipl. ABVP, ACVO, who is the head ophthalmologist & geneticist, and is leading a
study of the silver gene and its effect on the eye of the horse, and is confirming new
findings on the Z gene.* I also spoke at length with the head of genetics at
University of California, Davis. The 3 scientists all confirmed a strong belief that
breeding the Z gene to the Z gene, is possibly resulting in a homozygous Z/Z color,
and is risking an ocular problem, which, could then be passed on through
generation after generation. The Z gene has just been identified in the last few years
and research is in its budding stages, however, certain facts are coming out and it is strongly
                suggested NOT to breed Z to Z and certainly NOT to breed relative to relative possessing the Z gene.
 

The gypsy world has but a few gypsy horses with the silver gene and all of them in
USA are closely related. Most all are from the Boss horse line. I own 4 adult silver
dapples, and have sold 3 of my silver dapple foals. I am very concerned that in our
gypsy horses, we must be careful not to cause any problems which can result from
breeding sons and daughters and aunts and uncles, let alone Z to Z! If I thought I
was wrong or had any doubts, I would not be concerned, but I do have 2 fine gypsy
silver dapple stallions that I intend to continue breeding and would rather not see
indiscriminant, uninformed breeders make mistakes which could affect us all
eventually. Our gypsy horses do not have a written history. Their true lineage is all
by word of mouth, gypsy to gypsy, and dealer to dealer, so we had no real
documentation until we decided to test DNA on the horses before registering them.
This is thanks to the USA’s gypsy breeders who want to set the record straight as
much as we can! I also suggest NOT registering ZZ, homozygotes to the silver dapple gene.


There will be those asking about the Rocky Mountain Horse and Icelandic horse
breeds. The RMH and Kentucky Mountain Horses, are more in abundance than the
gypsy horses that carry the Z gene, therefore more research is available within those
breeds. They have many ZZ running in their bloodlines, and the RMH do have ocular
changes as do the Icelandic’s with ZZ gene. If a ZZ horse does not produce a ZZ
when bred to a Z mare or stallion, the ZZ horse will pass the ocular change on and it
can lie silent in the Z horse. I have given the researchers from the Canadian
Veterinary School permission to come and check out our horses, and have contacted
as many other Silver Dapple breeders or owners that I know of, so we can help
research the silver dapple color in the gypsy horse. We have but 15 or so with the Z
gene in the USA who will be cooperative thus far. There is no charge for this service.
It is research being done in a scientific fashion to help learn more about the Z gene
and different breeds. All results are kept private.
If one is curious to speak with or write to me, I would welcome any questions and
would provide answers, and or referrals to the proper persons who have the proper
answers. Also, I would be happy to recommend the genetics lab where I have had
my testing done for those wanting accurate information.”
Contact Celeste Huston at by email or call 805-688-8020. You can visit her web site
at http://www.cielocelestefarm.com


Article from The American Gypsy Horse Breed Association
http://www.aghba.org/