Effect of time and depth of insemination on fertility of Bharat Merino sheep inseminated trans-cervical with frozen-thawed semen
Pregnancy was diagnosed by transcutaneous ultrasonography in 327 ewes of 2 flocks. In addition transrectal sonography was performed in 93 of these ewes. Two hundred and thirty six ewes were pregnant and 88 animals were non-pregnant. Criteria to assess the accuracy of transrectal and transcutaneous sonography were overall accuracy (correct diagnoses/all diagnoses), sensitivity (correct diagnoses "pregnant"/all pregnant animals), specificity (correct diagnoses "non-pregnant"/all non-pregnant animals), predictive value of positive diagnoses (correct diagnoses "pregnant"/all diagnoses "pregnant"), predictive value of negative diagnoses (correct diagnoses "non-pregnant"/all diagnoses "non-pregnant"). Accuracy, sensitivity, specificity, predictive value of positive diagnosis and predictive value of negative diagnosis were 95%, 95%, 91%, 99% and 71% with the transcutaneous sonography resp. 94%, 95%, 93%, 97% and 86% with the transrectal sonography. Accuracy of the transrectal examination was superior (100%; 26/26) to the transcutaneous approach (89%; 39/44) in early pregnancy (Day 22 to 90). Transcutaneous sonography was more appropriate during the last part of pregnancy. The results demonstrate that both methods allow reliable pregnancy diagnosis in sheep under farm conditions. Ultrasonic pregnancy diagnosis is of economical value, if pregnancy rate of herds is below 90% and the diagnostic accuracy reaches at least 95%.