Some say you can "make" a hen go broody, but I've never heard of any real success stories. (Maybe someone here has tried.) One of my friends tried, by putting a hen in a secluded darkened dog cage with a clutch of eggs she wanted hatched. While the hen sat on them, she wasn't truly broody, and left the nest unattended for too many long periods of time. My friend ended up putting the hen back in with the rest of the flock and hatching the eggs in her incubator.
I personally break a broody hen under 1 year of age, as they are usually trying to get into the "lay an egg" groove and don't need the extra stress of raising chicks. Our Jersey Black Giant started laying at 5 months and went broody at 6 months and at 8 months. We didn't let her stay broody and hatch a clutch until after she was 1 year old.
Remember that TRUE broodiness is a hormonal change that the hen goes through. She has no control over it. Being broody is very stressful on the hen, especially if they are young or not in excellent health.
