Effect of Dietary Calcium and Phosphorus Levels on Ultra-Filterable Calcium and Dialyzable Phosphorus in the Laying Hen

Laying hens were fed diets containing combinations of 2.6 or 3.6% calcium and .45 or .75% total phosphorus. After receiving the diets for 2 wk, blood samples were collected during a 24-h period at 6-h intervals and total calcium, ultrafilterable calcium and dialyzable phosphorus was determined on blood plasma. Plasma total calcium was higher (P less than .05) in hens that received the diets containing the higher level of calcium (3.6%), but was not influenced by dietary phosphorus levels. Overall in the experiment, neither the dietary calcium nor phosphorus levels had significant effects on the plasma ultrafilterable calcium or dialyzable phosphorus. However, at 0600 and 1200 h, dialyzable phosphorus levels in plasma of hens fed the diet high in both calcium and phosphorus was significantly (P less than .05) greater than that in plasma from hens fed diets low in both calcium and phosphorus. The time that the blood sample was taken had a significant effect (P less than .05) on plasma total calcium, ultrafilterable calcium, and dialyzable phosphorus.