Pregnancy Determination in Sheep
Accurate determination of pregnancy facilitates differential ewe management by allowing the separation of multiple pregnant ewes for supplementary feed and lambing supervision and the culling of nonpregnant ewes. Procedures for diagnosis of pregnancy can involve detection of ewes that do not return to estrus (nonmarking by ram or teaser fitted with 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 mating (detectable progesterone levels indicate an active CL); and laparoscopy (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 done most accurately transrectally. When imaging is done later in pregnancy, the ultrasonographic transducer is placed in the woolless area of both flanks and the beam directed forward and upward toward the last rib on the opposite side. It is possible to examine, at low cost, 100–150 ewes/hr and to accurately diagnose single and multiple fetuses.