I have foam sandwiched in my coop for insulation and my hens ate a little that was protruding at the ends of the lumber. They didn't get sick or have any problems. I don't think it could be good but it doesn't appear to be a big deal.
No problems for the chicken but eventualy there will be no insulation on the garage foundation. That is a problem for me. I am thinking about some corrugated metal along the foundation. May be expensive but peck proof.