Urinary excretion of calcium in the presence or absence of shell formation by chickens producing thick or thin shells

The pattern of urinary calcium excretion before and during shell formation was observed for White Leghorn chickens producing thick or thin shelled eggs. Urine samples were collected at 2.5, 7.5, 12.5, and 20 hr after oviposition. Urine was collected in a tube inserted to cover both ureters within the cloaca and calcium levels were determined by atomic absorption. Urinary calcium was found to decrease similarly in both shell lines from 44 mg % to 5 to 6 mg % during shell formation. When no shell was being produced, hens of both shell lines excreted calcium in the urine at 34 to 53 mg % levels throughout the 20-hr period.