biostudies-literatureSinclair-Black MOffice of Research, University of GeorgiaUniversity of Georgia103209https://www.ebi.ac.uk/biostudies/studies/S-EPMC10746567biostudies-literatureUnknown103(2)Maintenance of calcium and phosphorus homeostasis in laying hens is crucial for preservation of skeletal integrity and eggshell quality, though physiological regulation of these systems is incompletely defined. To investigate changes in mineral and vitamin D₃ homeostasis during the 24-h egg formation cycle, 32-wk-old commercial laying hens were sampled at 1, 3, 4, 6, 7, 8, 12, 15, 18, 21, 23, and 24 h post-oviposition (HPOP; n ≥ 4). Ovum location and egg calcification stage were recorded, and blood chemistry, plasma vitamin D₃ metabolites, circulating parathyroid hormone (PTH), and expression of genes mediating uptake and utilization of calcium and phosphorus were evaluated. Elevated levels of renal 25-hydroxylase from 12 to 23 HPOP suggest this tissue might play a roPoultry scienceCircadian regulation of calcium and phosphorus homeostasis during the oviposition cycle in laying hens.PMC10746567000338Garcia-Mejia RAArbe XCavero DBlair LRAngel REllestad LESinclair-Black MfalseCircadian regulation of calcium and phosphorus homeostasis during the oviposition cycle in laying hens.Maintenance of calcium and phosphorus homeostasis in laying hens is crucial for preservation of skeletal integrity and eggshell quality, though physiological regulation of these systems is incompletely defined. To investigate changes in mineral and vitamin D₃ homeostasis during the 24-h egg formation cycle, 32-wk-old commercial laying hens were sampled at 1, 3, 4, 6, 7, 8, 12, 15, 18, 21, 23, and 24 h post-oviposition (HPOP; n ≥ 4). Ovum location and egg calcification stage were recorded, and blood chemistry, plasma vitamin D₃ metabolites, circulating parathyroid hormone (PTH), and expression of genes mediating uptake and utilization of calcium and phosphorus were evaluated. Elevated levels of renal 25-hydroxylase from 12 to 23 HPOP suggest this tissue might play a ro2023-01-01T00:00:00Z2023 Nov2025-04-04T14:12:46.724Z2025-04-04T14:12:46.724ZS-EPMC107465673805212910.1016/j.psj.2023.103209