Lipid metabolism and the laying hen: I. Plasma-free fatty acids and the onset of laying in the domestic fowl

It has been found that the onset of laying in the domestic fowl is preceded by large increases in the plasma-free fatty acids, total lipids and phosphoproteins,the quantities of these components decreasing markedly when laying commences. No such changes were detected in the cockerel on coming to maturity. When intermittent egg laying was induced by decreasing the duration of exposure to light a cyclical rise and fall of the plasma components was found to be associated with oviposition. The clearance rates of [ 14C]palmitate from the plasma of the laying hen were not markedly different from those of the immature pullet; the flux was related to the concentration of free fatty acids in the plasma. It is suggested that the decrease in the concentration of the plasma fractions results indirectly from a decreased gonadotropic stimulus of the ovary following ovulation and is not simply due to the removal of lipid and phosphoprotein as egg-yolk materials.