Changes in plasma calcium, phosphorus, lipids, and estrogens in turkey hens with reproductive state

Plasma calcium increased during the two weeks prior to first egg. The increase was in the protein bound (CaB) but not the ultrafilterable (CaU) fraction. Plasma neutral lipids (NL) and low density lipoprotein fraction (LDF, d < 1.006) increased similarly to CaB. Free fatty acids (FFA) had a transitory increase at first egg but then returned to levels not different from those when the hens were immature or in a reproductive pause. Plasma total phosphorus (Pt) increased similarly to CaB. This increase was associated with the protein (Pp) and lipid (Pl) phosphorus fractions. No change was noted for inorganic (Pi) phosphorus. Total plasma estrogen (Et), as estimated with radioimmunoassay utilizing an estriol antiserum, increaed similarly to CaB. Most of the increase was in an unidentified estrogen (Eu) fraction, but a sustained increase was also noted in the estrone (El) fraction. Estradiol (E2) levels did not differ with reproductive period. Simple correlations were calculated between all factors within the stimulatory and laying periods. In general, all correlations except those with diffusible calcium (CaD), FFA, and E2 were positive, relatively high (> .6) and significant (P < .01). The correlations tended to be greater in the stimulatory period than in the laying period. Partial correlations of the three estrogens with the other factors were calculated for the stimulatory and laying periods. The partial correlations of Eu were significant for all factors except CaD during the stimulatory period, but only with FFA, Pp and Pi in the laying period. The partial correlation of El with LDF was significant in the stimulatory period, and for LDF, NL, and Pi in the laying period. Partial correlations of E2 within the stimulatory period were not significant, but in the laying period a significant partial correlation with NL was noted.