Direct estimation of oestrone sulphate in sow serum for a rapid pregnancy diagnosis test.

An antiserum raised against oestrone-3-glucuronide-BSA was used for the direct radioimmunoassay of oestrone sulphate in pig serum. The method has a minimum sensitivity of 0.2 ng/ml and is potentially an accurate pregnancy test in pigs. Serum oestrone sulphate concentrations were less than or equal to 0.5 ng/ml in non-pregnant cyclic sows and greater than 0.5 ng/ml in pregnant sows bled 26-29 days after service.