Ok...now I'm confused. I've been feed Dumore Starter/Grower to my 4 ladies from the beginning to present. They're now 17 weeks old. I have not added grit at all to the feed. No issues with digestion, etc... They forage in the run and have fresh grown forage seeds that sprout to eat. Was I supoose to add oyster grit to the DuMore?
Assuming you are in the USA like I am:
"grit" is pices of rock. It stays in the gizzard to grind up feed.
"oyster shell" is a source of calcium. Hens need a lot to make eggshells. It may be actual shells from oysters, but may contain other things that also provide calcium to hens.
In other countries:
Labels vary, and I don't know them all. Some places say "oyster grit" where the US product usually says "oyster shell." The word "oyster" is usually a good tipoff that it provides calcium, not hard rocks for grinding food.
I would not add grit, oyster grit, oyster shell, or anything of the sort to the feed itself.
But I would provide oyster shell in a separate dish, so the hens can eat the amount they need. They are usually pretty good at getting the right amount. A starter/grower feed does not provide enough calcium for laying hens, so they really do need an extra source of it.
I don't know whether you need to provide grit (rocks for grinding food) or not. They may be getting enough from the soil in the run, or they may do a little better if you provide a separate dish of grit as well. If they seem healthy, I would say it's not a big deal to choose one or the other, so do what makes you happy in that respect.