Dun,
If the good Doctor went 4 generations deep daughter back to sire it would have looked like this:
1st Inbreeding=75% EXT
2nd Inbreeding=87.5% EXT
3rd Inbreeding=93.75% EXT
4th Inbreeding=96.875% EXT
Now it was his "experiment" so to each his own, but clearly the good Doctor has no real world understanding on how to inbreed livestock! With that said, the fact that he had a healthy 93.75% daughter of EXT to breed back to stands as a testament that when using sound genetic stock to begin with, that you can get away with some quick and intense inbreeding with no problems whatsoever. I submit also that with another daughter inbred to the same degree, or perhaps even that same one again he could have gotten a good healthy 96.875% calf, but I believe he went about breeding heavily on EXT in the wrong manner to establish a good solid program.
An infusion of some other EXT based blood would have kept his options broader, while keeping the percentage of EXT blood still rather high. You don't necessarily want to raise the percentage of a particular individual in your breeding program as abruptly as this Doctor did, but you want to raise your Wright's Inbreeding Coefficient to high levels, while culling out all of the undesireable specimen. SELECTIVITY is the name of the game when dealing in family bred stock. When you get the WIC% high, then you have a good chance of a calf coming out just like one of the parents rather than the great great grandsire. I belive judicious use of inbreeding in the beef breeds would give even more predictability to offspring and that family bred sires or dams would prove to be better producers hands down than other bulls or cows of the breed. It takes some knowledge as to how to do it properly though; most never do, and and by the time the few do figure it out................................. they are close to dead!
DOC HARRIS pointed out on the cloning thread one of the keys to understanding breeding, and that was his work with something as simple seeming as Chinchillas, and he also had valuable experience with Akita dogs.
Back to the original post of being able to breed daughter to sire, son to mother, half brother to half sister........and all of those F1 inbreedings...... shouldn't be a problem whatsoever although expect some reduction in size and an increase in consistency.
:cboy:
