Pregnancy diagnosis in sheep: review of the most practical methods.

Various practical methods have been used for pregnancy diagnosis in sheep. Both pregnancy and fetal numbers are accurately diagnosed by using radiography after day 70 of gestation. Rectal abdominal technique detects pregnancy with an accuracy of 66 to 100% from d 49 to 109 of gestation, however, it has a low (17 to 57%) accuracy for determining multiple fetuses. Progesterone assays have a high sensitivity (88% to 100%) and a low specificity (60% to 72%) at d 16 to 18. Estrone sulphate assay accurately detects pregnant ewe at d 30 to 35. Ovine pregnancy specific protein B (PSPB) assay accurately (100%) detects pregnancy from d 26 after breeding onwards. The accuracy of progesterone, estrone sulphate and oPSPB assays for determining fetal numbers is relatively low. A-mode and Doppler ultrasonic techniques accurately detect pregnancy during the second half of gestation. Fetal numbers cannot be determined by A-mode ultrasound, while the Doppler technique needs experience to achieve high accuracy. Transrectal B-mode, real time ultrasonography identifies the embryonic vesicles as early as d 12.8 after mating, but the sensitivity of the technique for pregnancy is very low (12%) earlier than 25 d after mating. Transabdominal B-mode ultrasonography achieved high accuracy for pregnancy diagnosis (94% to 100%) and the determination of fetal numbers (92% to 99%) on d 29 to 106 of gestation. Real-time, B-mode ultrasonography appears to be the most practical and accurate method for diagnosing pregnancy and determining fetal numbers in sheep