Equine dwarfism is a genetic defect which causes reduction in growth and body deformations, you can also see it as a developmental bones disorder. This disease ends in health restrictions and restricts dramatically the life quality on each dwarf individual.


This is a recessive trait.


The different mutations show up in different phenotypical defects, which also can be combined.


You will find a special gentics topic on the special side of ACAN and Del dwarfism on the right side above the flags.

Graphic by Liz C./Threnody works
Graphic by Liz C./Threnody works

Misbelief No. 1: The inheritance IS NOT dominant! Would it be dominant only one allele passed to the foal would show up in dwarfism. But this is not true. A rezessive inheritance will only show up when two alleles (one by each parents) are passed and will show up in a trait (in this case dwarfism). If you have a dwarf foal both parents inherited a dwarfism mutation on that foal.


Rezessive alleles only show up in a phenotype when they are homozygous. In reverse that means if a horse carries only one allele (heterozygous) you can see it on its phenotype, you call this horse a carrier because it can inherit this allele.


Do you breed carriers (see table above) you can get normal/healthy foals, carrier foals but also dwarf foals.


The danger is that a recessive allele can be inheritet through generations without notice. And one day -BOOM- you will have a dwarf foal.

Misbelief No. 2: Stallions were to be said to inherit dwarfism. This is not true. Now it is proven that dwarfism is a rezessive genetic disease and both parents need to inherit it for getting a dwarf foal. Equine dwarfism IS NOT linked to a special sex.

The above table shows mating carriers. As mentioned above here you can breed normal/healthy foals, carrier foals and dwarf foals.

Misbelief No. 3: Normal looking horses will never breed dwarf foals. That´s proven not true! Also "normal" and "healthy" looking horses can be carrier. Mating these can produce dwarf foals. This recessive trait can be inherited over generations without notice.


Mrs. Marleen Binder

RIP: Daisy, skeletal atavism dwarf, 2006
RIP: Daisy, skeletal atavism dwarf, 2006