Author
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Richards, Mark |
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Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/29/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Low hatchability is a problem that continues to plague the poultry industry. Proper nutrition, specifically trace element nutrition, is a critical aspect of ensuring the normal course of embryonic development within the egg culminating in a sucessful hatching. This report decribes how the hen deposits the required amount of each trace element into the yolk of the egg and how the embryo and its associated membranes utilize these trace element stores during its growth and development. The mechanism involves the coordinated actions of the yolk sac and the embryonic liver to mobilize, transport and store trace elements during development. Such information is useful to scientists studying avian embryonic development as well as those interested in egg nutrient quality. It will also help assess the impact of varying levels of specific trace elements on hatchability of fertile avian eggs. Technical Abstract: Trace mineral metabolism in the developing avian embryo begins with the formation of the egg and the trace mineral stores contained within it. Vitellogenin, the yolk precursor protein, serves as a trace mineral transporting protein which mediates the transfer of these essential nutrients from stores within the liver of the hen to the ovary and developing oocyte and hence to the yolk of the egg. Lipovitellin and phosvitin, derived from intraoocytic proteolytic processing of vitellogenin, are also trace mineral binding proteins which form an important storage site within the granule subfraction of yolk. The mobilization and uptake of egg trace mineral stores is mediated by the extra-embryonic membranes, principally the yolk sac membrane. The yolk sac also serves as a short-term storage site for trace minerals. Because it is an important site of plasma protein synthesis, the yolk sac has the ability to regulate the export of trace minerals to the embryo during development. Within the embryo specific metalloproteins function in the interorgan transport, cellular uptake and intracellular storage of trace minerals. Thus, embryonic trace mineral homeostasis is established through the coordinated actions of the yolk sac which mobilizes and exports trace minerals derived from egg stores, the vitelline circulation which transports them to the embryo, and the liver which accumulates trace minerals and distributes them to the rest of the tissues of the embryo via the embryonic circulation. |
