Rob, not sure about chickens, but with ducks it's perfectly okay to breed daughter back to father and son back to mother. There's a lot debate about siblings. I spoke a bit with a very good breeder about linebreeding/inbreeding. He did some experiments 20 odd years ago and found that consistently he didn't find problems until around the 7th generation. He doesn't breed that far along, but he wanted to know "with his own eyes" when problems began developing. We also spoke some about egg color genetics (ducks don't get the variations in egg color that chickens do, but occasionally you get some neat ones and he bred ducks for egg color for a bit before he let that project go in favor of other things he was more interested in). I wrote it down somewhere. I have a long work day today and if someone doesn't get back to you before I can, I'll look it up and tell you what he said.
