Genetic Defects

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stormy

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I guess I would like to see one more clarification before this closes. A lot of times we have postings about genetic defects on the forum and consistently the reply is must be a dwarf. I know you have addressed this in part while answering other questions but could you, for clarification, cite some common genetic defects or spontaneous mutations that are seen in horses of all breeds and by themselves are not necessarily indicators of dwarfism, but may still be heritable.
 
"cite some common genetic defects or spontaneous mutations that are seen in horses of all breeds and by themselves are not necessarily indicators of dwarfism, but may still be heritable."

Well for clarification, spontaneous mutations you are probably refering to are probably when a foal is born and it has crooked legs, club footed, or a parrot mouth or monkey mouth, or maybe cow-hocked and neither parent is showing those characteristics, or might be to a degree. Those defects most likely are recessive inferior genes that both the parents are carrying and the foal got both of the genes to express the defect. It was not spontaneous, those things are ont known as to how dominant or recessive due to breed variations, but these defects are usually inherited.

Now if you are refering to congenital malformations that occur during development then there is really nothing anyone can do. Those are things that happen spontaneously and are possibly not inheritable, some might be inheritable but as of yet are undetermined, ie, micro-opthalmia in horses. A good reason why it is still considered just congenital and not inherited yet, is that it is so rare when it happens. I have not read any cases yet where multiple afflicted foals have come from the same mate pairing. Meaning I have not read anything yet where two horses have produced more than 1 afflicted foal. These kind of spontaneous congenital malformations we cant control.

Any of the defects I listed so far I would not considered themselves alone characteristics of dwarfism. Just being monkeymouthed does not mean you are a dwarf nor even have a dwarf gene. You most likely have inherited a recessive undesired trait that neither parent is expressing due to them having normal dominant genes showing its trait.

Some traits are structural that someone might confuse with being a dwarf, like short legs that are proportional, meaning upper and lower leg bones are proportional to themselves, but you have a horse that is really long bodied, big head, and short neck. Well to me, most likely you have just a horse with undesirable traits, not dwarfism at all. Those things happen, we are breeding animals with genetics we cannot totally control, we are not manufacturing an idealized horse from an assembly line.

There are too many defects, whether inherited or congenital to list out that have nothing to do with dwarfism. A good large horse conformation and breeding book will be able to give good detail and pictures that are inferior traits that have nothing to do with dwarfism themselves alone.

Maybe more breeders should take a hard look in the mirror at yourself and see what is not "ideal" in the human's eyes.

Then take a look at the breeding (mating) decisions you made and take a hard look at the results. Now, how many of the resulting foals look like what you "wanted" to have, or thought you would have. After really being critical and if you got higher than 50% you are doing good.

Remember, Mother Nature wants genetic variation, this ensures the most viable genetics are spread out to ensure the perpetuation of a species, and organisms in general, plant or whatever. The way genes are inherited ensures some variation no matter how true breeding an animal is.

John
 
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