I always have them available. Younger birds may try oyster shell but shouldn't want to eat it past testing it out. I always have grit offered too (chicks receive grit from the very beginning with me) because I don't have particularly rocky soil and it's cheap digestive insurance.
Sorry I added on to my original post after thinking about it. So here's the extra info that would've helped: If you provide a source of calcium on the side you can feed that to them for life, or switch over to layer if that's your preference once everyone is actively laying.
Every bird is...
Grower will be fine, or all flock - nutritionally they're usually about the same. If you provide a source of calcium on the side you can feed that to them for life, or switch over to layer if that's your preference once everyone is actively laying.
Scratch and corn are optional treats and...