CALCIUM HOMEOSTASIS IN IN OVO AND EX OVO TURKEY EMBRYOS

Calcium homeostasis of in ovo (normal) and ex ovo (shell-less) turkey embryos was investigated at 15, 18, and 21 days of incubation. Hypocal cemia and an elevation in circulating 1,25(OH)(2)D-3 in ex ovo embryos were observed by 15 days. Calcium and phosphorus concentrations in fe mora and tibiae in ex ovo embryos were significantly lower compared to their normal counterparts. These results suggest that shell calcium m obilization is required prior to 15 days of incubation for maintaining serum calcium and supporting bone mineralization. Furthermore, the el evation of 1,25(OH)(2)D-3 is indicative of a functional calcium homeos tatic mechanism responding to the absence of the primary calcium sourc e (eggshell) during the second half of turkey embryonic development.