Naaaa1 Bruno I respect a lot of your comments but this one you are bullsh##ing or misinformed.
A good breed of chicken for laying will lay around 300 eggs per year but some lay a lot less, chichen farms run on a two/three year cycle depending on the breed and average out put per battery, they are then culled for the soup making or animal feed, the sheds are cleaned out and a new batch of pullets arrives
We have had chickens laying good up to four years old
Table chickens are days old then kept in a communal shed and culled about 20 weeks, they are culled and the whole shed cleaned out, customers like M&S stipulate food aditives allowed in the feed,
I agree a pigeon may not suvive wholly on hen pellets due to them needing seed to keep the gizzard healthy but the are a great source of calcium and protein, feral pigeons live in selected areas and thrive well on non seed based food
A chichen only lays every day because their eggs are taken away, if you left them they would lay a clutch and then get broody and incubate them