Detection of pregnancy in ewes with the ultrasonic Scanopreg

The accuracy of the ultrasonic Scanopreg was evaluated in tests with 24 commercials, West Virginia ewe flocks. Two Scanopreg units were used to check for pregnancy in 1,644 ewes that had been exposed to rams during the fall breeding season. Predictions were compared against lambing records. Possible accuracy errors were: type 1 (ewes diagnosed pregnant but failed to lamb) and type 2 (ewes diagnosed open but subsequently lambed). Type 1 error rate for 1,270 ewes was 1.2%. Type 2 error rates were 55.2, 15.5, 6.2, 1.1 and 4.0% for ewes pregnant less than 60, 60 to 69, 70 to 79, 80 to 120 and greater than 120 days at diagnosis, respectively. Accuracy of diagnoses during late pregnancy (greater than 120 days) was increased if obviously pregnant ewes were sorted out before testing. The combined error rate (all type 1 errors + type 2 errors for ewes 80 to 120 days pregnant) for 1,018 ewes was 2.5%. Ewe age had no apparent effect on type 2 error rates for ewes 80 to 120 days pregnant. Among flocks, type 1 and type 2 error rates varied from 0 to 11.8% and 0 to 7.1%, respectively. Variations in accuracy among flocks were associated primarily with undetected abortions (type 1 errors) and operator inexperience (type 2 errors). Scanopreg accuracy was not affected by individual units or inclement weather. We concluded that the Scanopreg is accurate and can be a reliable management tool if used to test ewes 80 to 120 days after they have been exposed to rams.