Odd way to find my site, yet a few have (through my Salem chicken updates). So to prevent any readers from food poisoning, I’ll answer in it’s own post:
The smell is from bacteria. Lots of bacteria. Bacteria decomposes food, makes you sick and STINKS. If it smells bad, throw it out. Don’t think cooking it to the recommended temp or higher will kill everything – to kill some bacteria it has to be basically boiling for 15+ minutes. Chicken that hot for that long? Blech. Throw it out. And don’t give it to fido unless you want an outragious vet bill and/or a dead puppy dog.