[Reliability of pregnancy diagnosis in sows using direct radioimmunoassay of estrone-sulfate].

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