I am heartbroken. I was trying to raise an offspring of my favorite Barred Rock hen, who will be 5 in March. A friend's broody hen hatched one of my hen's eggs for me on October 15. The chick was an only chick, but it was doing fine and seemed so healthy and happy. The chick was found dead in its nest yesterday, just 3 days short of 8 weeks old, fully feathered. I am trying to figure out what could have gone wrong... Could the mother hen's egg have had a problem? She is almost 5, after all. Could it be that just as older women tend to give birth more frequently to children with birth defects, could it be that older hens are more likely to have chicks with defects? I have researched this, but I can't find any information. Does anyone know an expert in the matter? The rooster who fertilized my hen's egg is 3 years old and is not related to the mother hen. None of his offspring who have hatched have died, except this one. My friend, whose hen hatched the egg for us, took such good care of the chick. She would let it sleep inside her house at night until recently, when it was fully feathered. Her husband complained that the chick was making too big of messes on their wood floor and wanted it to start sleeping outside in their coop. The weather here recently has been uncharacteristically warm for December-- no lower than the 30s at night. Do you think it more likely that the chick was killed by the cold shocking it or by a birth defect?