Originally Posted by rookie
ahh line breeding vs inbreeding. It gets wooly I am not a fan of it in any way shape or form. I think it can result is bad situations. I really worry about breeding programs that are based entirely on line breeding. Its part of the reason there is such an issue with cancers in various purebred dogs (goldens in particular). I know there is a train of thought that says if you inbreed/line breed through the genetic bottle neck you end up with stronger genetics by weeding out the weaker. I am not sure I fully support that idea. Most lab mice are the result of line breeding intensely which is why we can create mice without immune systems and with certain genetic diseases. Just look at the banana, which is the result of inbreeding extensively for generations and any new or modified banana virus would basically kill the entire worlds supply of bananas. Likewise, cheetahs are so inbred that they are basically all twins (they seem to be doing okay though).
Your foal will probably be fine as its probably not generations of line breeding but an isolated event.
I would worry less about lethal white (you can't do anything about that at this point in the game). I would have a really good vet on call and have a good foaling area and foal watch! Mini's are known for trouble delivering. They seem to be particularly prone to "red bag" deliveries in which the placenta prematurely detaches, depriving the foal of oxygen. This results in a dummy foal, where the foal looks normal for the first few hours and then gradually fades it forgets how to nurse, wanders far from the mother and ends up with numerous other issues. You can reduce red bag risk by knowing how to identify it and if you see it to call the vet ASAP while removing the placenta from the foal and delivering it as fast as possible. This has nothing to do with genetics and everything to do with bad luck.
I think you have missed THE most important point here. Inbreeding and linebreeding DO NOT CAUSE problems. Whatever problems there are expressed in the offspring, were and are, there all the time.
This is where responsible breeders, know everything they are able to discover, about the animals in the pedigree, of the dogs/horses they are breeding. Without knowledge, a complete outcross (difficult to find in most purebred animals today) or even the cross of two completely different breeds, does not mean certain genetic defects will not show up in the offspring. Just look at how many dog mutts, have dreadful genetic problems.
It all depends on the breeder, how responsibly they have investigated the background of the animals they are breeding and of course, if they have done all the necessary genetic testing.