Blood samples were drawn from laying hens via a brachial vein cannula at 2-hr intervals for 34 to 72 hr, and plasma was assayed for corticosterone (B). Concentrations of B, relative to photoperiod and irrespective of the time during the laying sequence, were highest 4 hr after the onset of the photoperiod, and had decreased to lowest values 4 hr before the onset of darkness (photoperiod 14L:10D). There was a surge of B coincident with the time of oviposition. The elimination of the oviposition-related peak of B (by examining concentrations during the morning of the first ovulation in the sequence) shows that the diurnal peak of B actually occurs approximately 2 hr after the onset of light, and that there is no surge of B 4 to 8 hr preceding ovulation as occurs for progesterone, the estrogens, and testosterone.
All Science Journal Classification (ASJC) codes
- Animal Science and Zoology