November 2007 "Ask the expert" Special Q and A Webinar with John Eberth sponsored and provided
exclusively by Lil Beginnings about the genetics of Dwarfism in the Miniature
Horse.
Credentials (as of Nov. 2007) as follows: B.A. in Biology, minor in biochemistry currently working
on his M.S. and PhD in Equine Genetics (concurrently)
at the University of
Kentucky Maxwell H. Gluck Equine Research Center
Owner of Arion Management Inc.
Licensed AMHA judge and currently working on his AMHR and ASPC cards
Please
click here to read our archived transcript of this historic online
event.
2013 Masters Thesis by John E. Eberth
Chondrodysplasia-Like Dwarfism in the Miniature Horse
University of Kentucky https://uknowledge.uky.edu/gluck_etds/11/
Dwarfism is considered one of the most recognized congenital defects of animals
and humans and can be hereditary or sporadic in cause and expression. There are
two general morphologic categories within this vastly diverse disease. These
categories are disproportionate and proportionate dwarfism and within each of
these there are numerous phenotypes which have been extensively described in
humans, and to a lesser extent in dogs, cattle, mice, chickens, and other
domestic species. Ponies and Miniature horses largely differ from full size
horses only by their stature...
Copy and paste the link above or download and read a copy of Johns thesis
HERE
Thank you so much John!
November 2013 The ASPC/AMHR Board of Directors voted at Convention that once
available, members would be able to record Dwarf test results on their horse's
registration papers.
Having the results recorded will incur a registration paper update fee just like
adding color test results (which AMHR will also do).
** Miniature Horse dwarfism Testing is Now Available! April 10th 2014
This is one of the most historic days for the Miniature Horse World!! Thank you
John for your tireless work.
ACAN Dwarfism Mutations in the Miniature Horse
Four mutations in the ACAN gene have been found in Miniature Horses associated with a dwarf phenotype by John Eberth, MS, working in the lab of Dr. Ernie Bailey at the Gluck Center. It is important to test breeding stock for these mutations because at least one of these mutations is lethal in combination with any of the other mutations causing early pregnancy loss. Care must also be taken in breeding two horses together that are carriers for Dwarf mutations, as the presence of two mutations in any combination will lead to early abortion or live foals with a range of physical ailments associated with the dwarf phenotype. Some of these physical ailments seriously affect the health of the horse and include breathing problems, malformed mouths which lead to eating difficulties, and abnormal bone growth leading to chronic soundness issues.
Horses carrying only one of the mutations are normal in appearance, exhibiting the desired stature and proportions the Miniature Horse should possess. There are four identified mutations, designated D1, D2, D3 and D4. The normal copy of the gene is designated as N.
The following table summarizes the effects of the various mutation combinations:
Examples of Normal Phenotypes
Examples of Dwarf Phenotypes
The genotypes D3/D3 and D4/D4 have unknown effects, as no samples with these genotypes have been found so far.
D1 and D2 were the most common mutations found in the pilot study. Since D1 is lethal in combination with any of the other mutations, it is recommended that D1 carriers (N/D1) only be bred to horses that do not carry any other Dwarf mutation.
Dr. Kathryn Graves
Director, Genetic Testing at Gluck
1400 Nicholasville Rd.
Lexington, KY 40546-0099
859-218-1165
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