Thanks Karen. I was not aware of the 3 week immunity from hatching deal. So it makes sense to get them exposed to soil right from hatching, right?
I don't know the exact time span, but it does vary by species (mammalian is typically 4-6 weeks, antibodies are found in the colostrum). I say 2-3 weeks on chicks, simply because they are further along in development than most mammals at birth.
so yes, continued exposure from day 1 will help them develop their own immunity to anything and everything that comes along IMO...