So, this link might help:
https://www.merckvetmanual.com/poul...t-poultry/nutritional-requirements-of-poultry
Note that the charts expand if you hit the X made of arrows in the lower right corner of the chart. You can get info about different ages and even about the requirements of white vs brown egg layers (they are different!!!!!!!! - I had no idea)
Do these numbers means(2850) that a chicken needs that many calories per day?