MSRminis,
There are no known or proven environmental causes to any of the dwarfisms in the Miniature horse.
The reason why this would be impossible for any of the dwarfisms to be due to a specific environmental factor is that it would have to be something to cause the exact mutation every time in every dwarf produced and it would have to occur all over the world.
These dwarfisms are seen in other parts of the world, and in Canada, and all over the US. The statistical chances of a single environmental factor to cause an exact mutation in the same gene to cause the identical physical condition of dwarfism all over the world for just ONE of the types I have characterized is just HUGE. This means hundreds of millions or hundreds of billions and more to one. I dont know how one would even try to calculate those chances. You would have to take into consideration all possibilities of the variances in concentration, quality, and mutagen power of the environmental factor throughout the world, all of the variations in the number of genes in the horse, the total number of genes, the horses genetic incompetetence of the DNA healing process of the fetus or mare and its eggs during oogenesis and the stallion for semen during spermatogenesis, variations in other mutagen causing agents that could enhance or restrict the specific mutagen envirnmental factor, and on, and on, meaning you have a much higher chance of winning every lottery in the US than that occuring in the Miniature horse all over the world to give you all the same dwarfism seen.
Now there are known environmental mutagens in the world that are known to cause some types of dwarfism in certain organisms, but those are shown to be very specific within a certain local area, meaning, isolated areas with organisms experiencing the exact same environment with the mutagen causing factor, i.e. a single farm with a mutagen causing agent on the farm, also chemicals or environmental factors that cause metabolic diseases in an organism are already developing, and these still are isolated cases.
I hope this helped.
John
