I've had quite a few assists that have been completely successful with a strong chick that went on to grow and become an active flock member. There's no right or wrong answer here. IMO, when it becomes evident that the chick is destined to fail on it's own, I will assist. My thought process goes like this: Incubation is an artificial process. We are doing our best to mimic the perfection provided by the broody hen. There are so many things that even an accomplished incubator may do wrong that could have a negative outcome. So, slow but sure... with the realization that my intervention may: kill the chick, save the chick, or produce a chick that will then need to be culled. If an internal pip goes overly long, (up to 24 hours) I might make an air hole in the air cell. If an external pip goes overly long (24 hours) or starts out strong, and fails to progress and is quiet but still alive after an extended time, I will then enlarge the pip, assess blood vessels, and most likely put that egg back in the bator for an other 1/2 day before taking any action. When I do take action, I commit the time to finish the job. If the chick has been stuck in the shell for an extended time, that gives plenty of time for yolk and peripheral blood absorption, so the assist is minimal risk in both of those areas. As long as the baby can breathe in the shell, he won't die if you wait to complete the assist. Usually at this time, I'm dealing with dry membranes, so I fill a bowl with warm water, and peel the baby out while floating in the water in my hand. beware there is huge risk of aspiration if you allow even a drop of water to get on the chick's face. A quick towel dry and toss him back into the bator to warm up and rest. Often, by the next morning, I can't even tell which chick it was.
