I've only had one with special needs and that was due to delayed development because as a newbie I wasn't smart enough to check my brand new thermometer. (That was my big learning curve right there.) And he hatched out day 24. I didn't even know that there was anything wrong with his leg until he got bigger and heavier. Then I noticed how off his balance was. I was wondering why he didn't roost, but didn't think too much of it. Once I got the second coop finished and put the younger ones out there I decided to try him out there too. That's when I started to really realize exactly what his problem was. His "knee" joint is turned in. It didn't show and become apparent until he had gotten heavier. I never thought that he'd be able to go to the coop or be half as "normal" as he is. He surprises me daily with his strength and how well he functions. I am still concerned about what will happen this winter though as he can't roost with the rest.
I have a question maybe one of the long time raisers or genetics experts can chime in on. I never plan to use Peep, (my special needs roo) as a breeder, don't even think he can really complete the mating process even when he does try. BUT I am curious as to how birth defects from something such as a screwed up hatch due to low temps plays a part in genetics. Had he been incubated in the right conditions, chances are he would have been normal. Do defects from sub par incubation affect the actual genetic make up of the chicken and can it be bred down to offspring?
Theoretically, no... defects that happen from an outside source are not genetically passed down... although, there is theories about continued breeding of 'outside faults' eventually becoming genetic defects able to be passed...
But, it is extremely hard to guarantee that defects or faults are not from genetics in the first place... so for breeding forward a healthy generation, those 'should' be passed over in favor of more whole stock...
My shipped egg story...
I got a chance at some really nice rare eggs from a good, trusted friend... their stock is genetically sound, very healthy and she is a genetics whiz so I knew that what I was getting would be quality stock... after an initial shipping of eggs where the box got used for a rugby scrum, a secong batch was sent... to get odds weighed in our favor, the eggs were incubated until first veining and then placed under a dedicated Silkie broody... she did great and got 6 babies to hatch from 8 that started... one chick came out looking like it had had a stroke... literally... left eye was sunk in a bit, eyelid opening was smaller than it should've been and last 2 toes on left foot were useless... this is where we believe there is more damage done inside a yolk when shipped than we can see... also, with all my shipped eggs I always set my own eggs alongside as a control group... no issues in any of those chicks... and she had never had any chicks hatch in those lines with any defects... so... ??? Still won't use him for breeding, but he is a sweet bird and has a home with us for life...