Accuracy of Real-Time B-Mode Trans-Rectal Ultrasonography for Early Pregnancy Diagnosis in Crossbred Ewes

Abstract

The concept of doubling the farmer’s income in India can materialize early when recommended animal husbandry practices are adopted with a practical approach by the sheep farmers. One such practical and very useful technique is ultrasonography (USG) for early pregnancy diagnosis in ewes. In India, Sheep industry is mainly confined to small and marginal poor farmers with unavailability of cost effective technological aids to diagnose pregnancy early at the field level. The present study evaluates the sensitivity and specificity of trans-rectal USG to diagnose early pregnancy. Results of USG carried twice on day 25 and 45 post-mating on 60 crossbred ewes compared with the actual lambing data retrospectively. The accuracy, sensitivity, specificity, positive as well as negative predictive values for these tests were 91.7, 100, 78.3, 88.1, 100 per cent, respectively on day 25, and 100% on day 45 post-mating. Embryonic/fetal heart was also assessed using 6.0 MHz trans-rectal probe for confirming the pregnancy with viable embryo/fetus. The embryonic/fetal heart rate at day 25 (130.9±0.86) and 45 (127.3±0.81) post-mating were found to be significantly different (p<0.01) with decreasing trend with the advancement of age. The relative difference in specificity of technique on day 25 and 45 post-mating was assumed to be due to embryonic/fetal losses confirmed by absence of heartbeat on  day 45 post-mating.  The study results indicate high accuracy of USG for pregnancy diagnosis as early on day 25 post-mating in sheep, and multiple assessments during the gestation period can be a means to detect embryonic/fetal losses.