Plasma inorganic phosphorus concentration during eggshell formation. II. — Inverse relationships with intestinal calcium content and eggshell weight

Abstract

This paper reports two experiments. In the first experiment, 51 laying hens were killed at four different stages of eggshell formation (6, 10, 14 or 16 h after a previous oviposition). The individual contents of the duodenum and jejunum were studied for soluble Ca concentration (Cas). The Cas increased in the duodenum and the proximal jejunum during shell secretion (14 and 16 h) ; the values recorded in the distal jejunum were lower than those of the upper segments. At the same physiological stages, an inverse relationship was evident between Cas and plasma inorganic phosphorus content (Pi) (r = - 0.7 to - 0.8). A negative relationship was also calculated between the Pi value at 14 h and the shell weight of the last two eggs produced before slaughter. In the second experiment, blood samples were taken from 35 hens at 10, 12, 14 and 16 h after oviposition. The surface under the Pi curve was calculated for each hen and used as an estimation of bone mobilization. The weight of the shell secreted during the sampling period was negatively correlated with this Pi surface (r = - 0.68) when studied in a covariance analysis including egg weight. The different possible relationships among the factors of intestinal ability to absorb calcium, bone mobilization, inorganic phosphatemia and shell deposition in ute!o are considered.