My 2 girls haven't laid much recently -- they always slow down in winter anyway, and then they had the big upheaval of moving to their new coop. I checked the nest box Mon. a.m. -- nothing. Didn't check Mon. p.m. Checked this a.m. and there was an egg. It wasn't warm at all and the temp was down into the 20s last night. Is the egg usable? Should I keep it or toss it? Is there a way to know? If they laid it yesterday, then it was sitting there in freezing temps for 24 hours. ??? Thanks!