Good plan. I need another bag of feed next week. I think I will get layer feed and see how badly they complain!
So, as you all know, I have a large mixed flock.
As others have said, long term excess calcium is hard on Roos (any animals) internal organs, evidently particularly Kidneys & liver.
I feed organic feed, and can not get an organic all flock locally, they can't even order me some in, and with the amount of feed I go through i just can't afford the shipping to order online (I am in that bad place of needing a lot of feed, but not enough to order it a pallet at a time - 2,000 lbs.)
SO: My solution has been to mix my own 'all flock'. I use a good organic grower, and an organic, soy free layer - mix the 2 and add in supplements as I go. (minced garlic, brewer's yeast year round, dried kelp in the winter)
I vary my ratio of layer to grower throughout the year. Spring flush time (now through mid-to-late June) my ratio is 40% layer to 60% grower, summer with the heat and slight slow down, I drop it down to 30-33% layer, and in the moulting season through winter, I have the ratio between 20 & 25% layer (depending on how many young layers starting up I have - last year my chicks hatched late and very few started laying, so I actually went as low as 15% for a bit, but that is unusual)
They always have oyster shell and grit free choice, and once every week or two, I bake any eggshells I have, crush, and put out. Those get gobbled up right away, though - so they don't last more than 30 min. max.
Occasionally, I will have an older hen that is laying weak shells - depending on the situation, I will do one or more of the following:
Give the 1 (or 2 ) hens calcium (least preferred choice)
Separate them for a short time first thing in the morning and give them a warm* mash of straight layer, warm water, and maybe a bit of kefir - so they get a good 'dose' of calcium, then let them 'mingle'
Separate them first thing in the morning and give them warm* mash of the current mix, but mix in a bit of oyster shell....and, nearly always for this, a bit of kefir.
*Note: Warm in the cooler times of the year. If it is hot out, make a chilled mash....which basically means I prep it the night before and keep in fridge overnight (I have a counter height 'chicken fridge/freezer'.
I don't know if this helps at all - but you don't have to do Layer
or Grower
or All Flock You can mix them to get your own desired ratio of calcium!