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Abstract
Sixty-four New Zealand Romney ewes of known dates of conception grazing a white clover-ryegrass pasture were divided into 8 groups of 8 sheep. One group was slaughtered just before mating, and one of each of the remaining groups was slaughtered at 62, 81, 100, 115, 125, 135, and 143 days of gestation. At slaughter the conceptus was removed and the foetus, placental fluids, and uterus with placental membranes attached were separated. About half the ewes bore twins, and on the 95th day of gestation the ewes were X-rayed and thereafter the slaughter groups were made up of 4 single-bearing and 4 twin-bearing ewes. All of the singleton foetuses and one member of the twin pairs were dissected and the liver, lungs, heart, kidney, spleen, thymus, and digestive tract removed. The calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), potassium (K), copper (Cu), zinc (Zn), iron (Fe), manganese (Mn), and selenium (Se) contents of the foetus(es), foetal organs, and conceptus were determined. The rates of accumulation of Ca, P, Mg, Na, K, S, Cu, Zn, Fe, Mn, and Se into the foetus(es) and conceptus at the various gestational ages were determined from the slope of the curves relating the mineral contents of the foetus and conceptus to the gestational age.