Most things say around 16 weeks...But a whole lot of chickens don't lay til 20 weeks or later. So I'm not sure if 4 weeks of extra calcium is good for them, or bad. I use flock raiser with oyster shell on the side, because I had a mixed age flock in the coop and the adult chickens were eating all the chick starter...ALL of it. So, I switched to the flock raiser and it along with sudden comb growth let me know that 4 pullets were about to start laying...they went months totally uninterested in the oyster shell, and then one day they started eating it...a few days later---eggs. I also have a huge rooster that is an eating machine, and I have seen him more than a few times dipping into the oyster shells when I first refill the thing. All the chickens have to come see what I have, and they will all try it, but only a few of the layers will actually eat any of it, except the big old rooster who just chows down...once it isn't new I don't see him back at it. Blah Blah Blah. I figure I will keep on with the flockraiser and oyster shell. Because we have ducks and chickens now, and we're getting turkeys in May, so it just seems the easiest thing to use so I don't have to buy and store all different types of foods. Right now I have flock raiser, Chick Starter, and meat bird maker...I don't like looking like the weirdo with the flat cart piled high with feed bags at the farm store...people give me all kinds of strange looks. I guess I don't look like your traditional farmer or something. Either way...I like the flock raiser...
Sweet heyzoos I'm apparently feeling very chatty today.