Reliability of pregnancy diagnosis in sows by direct radioimmunoassay of estrone sulfate

Pregnancy diagnosis in sows using direct radioimmunoassay of estrone sulfate in the blood serum without sample extraction is described. It was found that for pregnancy diagnosis the period between days 22 and 30 of pregnancy can be used since in this period the estrone sulfate concentrations in all pregnant sows markedly exceeded those of 64 non-pregnant animals. The estrone sulfate estimation cannot be used for pregnancy diagnosis before day 22 and between days 30 and 40 because the estrone sulfate concentrations in most samples collected in these periods were lower than 4 nmol.l-1. (author). 1 fig., 6 refs