Quote:
https://www.backyardchickens.com/a/hatching-eggs-101
Researchers have found that lowering temperatures will prolong incubation,
HOWEVER it is favourable to do so at the end of incubation.
Day 19 & 20 Temp Min 98.0 Max 98.5
Day 21 Temp Min 97 Max 98.0
for more information please refer here:
http://www.hubbardbreeders.com/managementguides/Incubation guide (english).pdf
Quote: http://www.pasreform.com/academy/frequently-asked-questions/incubation/33-empty-shells-a-valuable-source-of-information.html