Plasma variation of transferrin-iron and phosvitin-iron during the laying period in chicken hens.

The distribution of plasma iron between transferrin-iron (Tf-Fe) and phosvitin-iron (Phv-Fe) over a 98 week laying period was established in hens. Six plasma samples were collected at random from a group of 20 pullets, starting when the birds were 20 weeks old. Samples were collected weekly until the 29th week and subsequently on the 41st, 62nd, and 98th weeks. Detailed assays were carried out to differentiate Phv-Fe from Tf-Fe. Phosphoprotein (phosvitin) concentrations were also determined. At the beginning of sexual activity, (23 to 24 weeks) females showed a parallel increase of Tf-Fe and Phv-Fe. During the period of maximum egg production 29 to 41 weeks) Tf-Fe was 65% and the Phv-Fe 35% of the total plasma iron. During this period the transferrin saturation reached a maximum of 80%; both transport mechanisms worked simultaneously. Estrogen administration to male chickens (2 injections of 5 mg/kg body weight) precipitated similar variation patterns of the two plasma irons over a period of 7 days. It is suggested that the estrogens were responsible for these variations.