Improving bone health and eggshell quality through maintaining a desired calcium homeostasis in laying hens
Loading...
Date
2023-02-25
Authors
Hui, Qianru
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Laying hens have an extra demand on calcium (Ca) homeostasis due to egg-laying. The calcium-sensing receptor (CaSR) plays a central role in Ca homeostasis. The thesis aimed to develop effective methods for maintaining desired Ca homeostasis in laying hens. The first study demonstrated that chicken CaSR (cCaSR) and chicken vitamin D receptor (cVDR) are widely distributed in the kidney, gastrointestinal tract, shell gland, and tibia in laying hens at different laying stages. The second study characterized cCaSR ligands in cCaSR-stably expressing HEK293 cells and investigated the binding modes between cCaSR and its ligands. Results showed that L-tryptophan (L-Trp) and inorganic PO43- are cCaSR modulators, acting as positive and negative allosteric modulators, respectively. The third study isolated chicken mesenchymal stem cells (MSCs) from broilers and layers and demonstrated that cCaSR and cVDR were expressed in broiler and layer MSCs. The osteogenic differentiation process in layer MSCs was faster than that in the broiler MSCs. L-Trp and 1,25-dihydroxycholecalciferol (1,25OHD3) were found to regulate proliferation and osteogenic differentiation in broiler and layer MSCs, depending on the modulator’s doses and treatment time. The fourth study was to investigate the interactive effects of Ca and L-Trp, and of Ca and 25-hydroxycholecalciferol (25HyD) substitution for vitamin D3 on egg production, eggshell quality, bone health, and calcium homeostasis in Dekalb layers from 26 to 29 weeks of age. Results showed that increased dietary Trp levels increased serum Ca level, eggshell quality, and tibia traits. An interactive effect was found that Ca continued to increase the relative eggshell weight and eggshell thickness as Trp level increased. However, 25HyD did not improve egg production, eggshell quality, and bone health. Taken together, the cCaSR and cVDR are widely expressed in laying hens. Ca2+ and L-Trp promoted osteogenic differentiation in chicken MSCs and they improved Ca utilization, eggshell quality, and bone health in laying hens. 1,25OHD3 can facilitate chicken MSC proliferation, but 25HyD did not promote egg quality and bone health in laying hens. The results provide evidence for the potential application of cCaSR modulators and different vitamin D3 sources to improve eggshell quality and bone health in laying hens.
Description
Keywords
Calcium homeostasis, Calcium-sensing receptor, Vitamin D3, Laying hens