Accurate determination of pregnancy facilitates differential ewe management by allowing the separation of multiple pregnant ewes for supplementary feed and lambing supervision, as well as the culling of nonpregnant ewes.
Procedures for diagnosis of pregnancy can involve detection of ewes that do not return to estrus (nonmarking by the ram or teaser fitted with a harness and crayon); transabdominal, real-time ultrasonographic scanning; rectoabdominal palpation (from 70 days); abdominal palpation (from 100 days); measurement of plasma progesterone concentrations 18 days after breeding (detectable progesterone levels indicate an active corpus luteum); and laparoscopic examination (from 30 days).
Real-time ultrasonography is a rapid, highly sensitive and very specific test for pregnancy diagnosis of ewes (and does). For detection of early pregnancy (eg, 20–40 days), it is most accurate when performed transrectally. When imaging is done later in pregnancy, the ultrasonographic transducer is placed in the most wool-less area of both flanks and the beam directed forward and upward toward the last rib on the opposite side. With appropriate experience and training, it is possible to examine, at low cost, 100–150 ewes/hour and to accurately diagnose single and multiple fetuses.