Lipid metabolism in the chick embryo: some recent ideas.

The transfer of lipid that occurs from yolk to embryo during the last week of development of the chick is associated with some notable changes in tissue lipid and fatty acid compositions. Recent investigations into the concentration changes of some of the major lipid classes and their fatty acid compositions within the yolk complex and embryo have enabled metabolic interpretation to be placed on several of these observations. As well as its central role in yolk lipid assimilation, the involvement of the yolk sac membrane in some specific yolk lipid changes before uptake by the embryo has been identified. Distinctive changes in the normal pattern of yolk lipid mobilization and utilization have been observed in eggs exhibiting low hatchability and in relation to the survival of chicks from very young parent stock.