EVALUATION OF FALSE ULTRASONOGRAPHIC PREGNANCY DIAGNOSES IN SOWS BY MEASURING THE CONCENTRATION OF UNCONJUGATED ESTROGENS IN FECES

On Days 26, 28, and 30 after AI, ultrasonographic pregnancy diagnoses were performed on 207 gilts and sows by using a 3.5 MHz linear-array t ransducer. Fecal samples were taken from the rectum after each ultraso nographic examination, and the concentrations of unconjugated estrogen s in selected samples (n=73) were measured by RTA. Fecal unconjugated estrogen concentration of 11.7 ng/g feces or higher was indicative of pregnancy. The overall sensitivity and specificity of the ultrasonogra phic test was 99% for farrowing sows and 73.1% for nonfarrowing sows. With one exception, sows with a false negative diagnosis by ultrasonog raphy on Day 26 were correctly diagnosed pregnant by elevated fecal un conjugated estrogens or repeated ultrasonographic examinations on Days 28 or 30. Return to estrus around the sampling period may cause false positive results in the unconjugated estrogen assay, while early embr yonic mortality can result in false positive diagnoses in both the ult rasonographic test and estrogen assay. Although there was a positive c orrelation between the concentrations of unconjugated estrogens in the feces and litter size at farrowing in the selected sows, it seems ver y unlikely that fecal estrogens can provide an accurate tool for predi cting litter size. (C) 1997 by Elsevier Science Inc.