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

Abstract

The usefulness of fecal estrone (E 1) measurement as a tool for pregnancy diagnosis was investigated. Concentrations of E 1 were measured in feces from pregnant and nonpregnant sows by a direct ELISA without extraction. Highly significant differences in E 1 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 E 1 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 E 1 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 E 1/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 E 1 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 E 1 concentrations in both nonpregnant and pregnant sows offers a suitable basis for the development of a simple, sow-side pregnancy test.