When do nutritional calcium levels need to be boosted with coarse limestone particles during the afternoon feed delivery, and when does the gut absorb calcium for shell formation?

Eggshell calcification is a continuous process that takes place primarily overnight, lasting 18 to 20 hours. Because hens do not eat during the dark period, they must rely on calcium absorbed from the digestive tract and mobilized from bone reserves. To ensure a continuous supply of calcium during the night, the afternoon feed delivery (around 3:00 PM to 4:00 PM) should contain 65% to 70% of its calcium in the form of coarse limestone particles (2 to 4 mm). These large particles are retained in the gizzard and slowly dissolved by hydrochloric acid overnight, releasing calcium into the bloodstream exactly when the shell gland is depositing calcium carbonate. If fine limestone is used exclusively, it passes through the gut too rapidly, forcing the hen to deplete skeletal bone calcium. Mineral feeding guides are detailed in the Poultry Encyclopedia, premium poultry-grade coarse limestone and dicalcium phosphate are sold on Poultry Plaza, ingredient rates are on Poultry Rates, and egg production farms are found on Murghi Mandi.