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Placental Transfer of Calcium in Pregnant Sows on Normal and Limited-Calcium Rations¹

Louisiana Agricultural Experiment Station, Baton Rouge

Abstract

Twenty-four yearling sows, maintained on normal (0.7%) and low-calcium (0.3%) diets throughout the final trimester of pregnancy, were administered a single tracer dose of Ca⁴⁵ citrate and killed 8 to 168 hr. later for radio-chemical analyses of fetal-maternal tissues. Data indicated sows on normal rations absorbed less Ca⁴⁵, transferred more total and radiocalcium to whole fetuses and deposited more of the absorbed Ca⁴⁵ in maternal tissues. Fetal calcium and Ca⁴⁵ concentration values were greater than those for dams, and tissue levels were lower in those fetuses from sows fed the low-calcium diets. Percentage and rate of distribution of Ca⁴⁵ transferred to litters were not different, but total calcium values for pigs from dams on the normal diets were higher (P<.01). Results indicate that maternal needs influenced calcium movement and transfer to fetuses, and fetal-maternal calcium equilibrium levels were lower when dietary calcium was restricted. Low calcium concentration in placenta and fluids suggested that maternal plasma was the primary fetal calcium source during the final trimester of pregnancy.

¹ Published with the approval of the Director of the Louisiana Agricultural Experiment Station, Baton Rouge. Grateful appreciation is expressed to Carol Bradley, Sharon Nicholson, William Whitfield and Paul Duplessis for technical assistance and to National Science Foundation (Contract 1944) for partial support of this study.

² Dr. H. Itoh, International Mineral and Chemical Corp., Skokie, Ill., Postdoctorate Research Fellow on leave from Faculty of Agriculture, Tohoku University, Sendai, Japan.