Pregnancy diagnosis in sows: direct ELISA for estrone in feces and its prospects for an on-farm test, in comparison to ultrasonography.

The usefulness of fecal estrone (E1) measurement as a tool for pregnancy diagnosis was investigated. Concentrations of E1 were measured in feces from pregnant and nonpregnant sows by a direct ELISA without extraction. Highly significant differences in E1 concentrations were found in feces from nonpregnant and pregnant sows (P = 0.016 to < 0.001). Pregnancy diagnosis on Days 26 to 32 after insemination, based both on fecal E1 concentrations as measured by ELISA and ultrasonography using a 5.0 MHz linear-array transducer, was performed in a group of 496 gilts and sows. The fecal E1 test had a sensitivity (correct diagnosis of pregnancy) of 96.5% and a specificity (correct diagnosis of nonpregnancy) of 93.6%, using 3.65 ng E1/g feces as a cut-off value. For ultrasonographic pregnancy diagnosis the test sensitivity and specificity were 99.3 and 92.5%, respectively. Although an increase of fecal E1 concentrations was noticed for increasing litter sizes, the results indicated that these concentrations could not be used to predict litter size. It is concluded that the distribution of fecal E1 concentrations in both nonpregnant and pregnant sows offers a suitable basis for the development of a simple, sow-side pregnancy test.