Pregnancy diagnosis in sheep and goats: a review

Abstract

During the last two decades, attempts have been made to diagnose pregnancy in sheep and goats by ultrasonic means. Between 60 and 80 days of gestation, an A-scan instrument is approximately 95% accurate and Doppler system is up to 100% accurate in diagnosing pregnancy greater than 60 days post-breeding. With real time B-scan ultrasound, pregnancy can be detected as early as 25 days of gestation. Fetal viability, fetal numbers and also the diagnosis of some reproductive tract disorders are possible. Determination of estrone sulfate assay provides a highly sensitive and specific pregnancy test for ewes and does 70 and 50 days post-breeding, respectively. Determination of progesterone on Day 20 of the gestation provides 90% accuracy in ewes and does but is not specific for pregnancy. Pregnancy diagnosis and fetal counts are possible using radiography 90 and 70 days of postbreeding in ewes and does, respectively, but is not feasible in the field. Rectal abdominal palpation is relatively inexpensive and easy to perform in the field in sheep with an accuracy of 90% at 60 days of gestation. It is unsuitable for goats cause of the risk of trauma, abortion or death. By Day 40 of gestation, an accuracy of 97% has been obtained using vaginal biopsies, but it requires laboratory facilities. Direct palpation of the pregnant uterus via laparotomy after Day 28 and Day 42 of gestation in ewes and does provides 92–100% accuracy, but has also limited field application. Abdominal palpation and ballotment are only effective during late pregnancy and do not give always reliable information. Pregnancy-specific antigen chorionic somatomotrophin in serum of ewes results in 97% accuracy 55 days post-breeding. Older techniques such as palpation of the cervix, mammary secretion and increase in body weight (BW) have been replaced.