Mary Fisher wrote:
They need grit which you can buy from poultry feed supplieers, as well as
oyster shell. Sand isn't the same as either. It's quite a complicated
process.

I grew up in a village store, and we used to sell all this stuff.
Layer's pellets, off-lay feed, brood feed, corn, mash etc. There were
3 grades of seashell sold, Oyster&Mussel (came from the essex coast),
White shell (mainly scallops) and a couple of patent brands which I
only stocked when we couldn't get the generic stuff. The white shell
was supposed to give the best results. Some brands of Layer's pellets
had the shell built in, others didn't. It was important to read the
ingredients [1]. I used to do that at the wholesale end, and only
stocked the calcium enriched ones. People still bought the shell. It
came pre-ground, but we had an old mill in the corner from the time in
the 1920s when it used to come in sacks from the railway station, just
as collected.

We used to sell derbyshire grit, but some places sold seasand as grit.
The birds need it to help process high-celulose feed before digestion,
and it has to be topped up quite regularly.

Old village hands used to starve the hens on Friday. The idea being to
discourage fussy eating. Fussy eaters could get an unbalanced diet and
lay less. Another trick was to use the friday fast to check feeding
rates. If the lay on Saturday and Sunday was just as good as during
the week then the daily feeding rate was too generous.

[1] brands without calcium were still high in protien, other minerals,
and vitamins. Different balance to brood feed.