Diagnoses of pregnancy were made on 110 Hereford cross Friesian and 69 blue grey (white shorthorn cross Galloway) cows between 92 and 202 days after last service using a real-time ultrasonic scanning instrument with a 3.5 MHz rectal transducer. Of the 174 cows which subsequently calved, one was wrongly diagnosed as non-pregnant. Of the five cows which did not subsequently calve two were diagnosed as pregnant and may in fact have been pregnant at the time of scanning. The overall level of accuracy of pregnancy diagnosis was 98.3 per cent. In further trials with 16 Hereford cross Friesian and 16 blue grey cows scanned at regular intervals between 20 and 140 days of gestation, pregnancy was diagnosed with confidence from 30 days, and relationships were established whereby gestational age could be estimated from measurements of certain uterine and fetal dimensions. Crown-rump length provided the most precise estimate of gestational age (residual sd +/- 4.5 days) and uterine diameter the least (+/- 12.6 days) with head length and the diameters of trunk, head and nose being intermediate (+/- 6.9 to 8.7 days).

Two trials were conducted on a total of 1120 ewes of four breeds to evaluate the use of real-time ultrasonic scanning as a means of diagnosing pregnancy, differentiating barren, single- and multiple-bearing ewes and determining actual fetal numbers in pregnant ewes. In trial 1 (566 ewes) the accuracy of an inexperienced operator, as judged against assessments of an experienced operator, improved from 81 to 100 per cent for the classification of ewes as carrying no, one or more than one fetus, and from 69 to 100 per cent for the determination of actual fetal numbers more than one. In trial 2 the accuracies of the same operator, judged against the lambing performance of 267 ewes, ranged from 90 to 97 per cent for both types of assessment, and for an experienced operator from 95 to 100 per cent (554 ewes). In both trials pregnancy was diagnosed with an accuracy of 100 per cent. It is concluded that real-time ultrasonic scanning of sheep between days 50 and 100 of gestation offers a safe and practicable means of diagnosing pregnancy and of determining fetal numbers. Accuracies of diagnosis of pregnancy of more than 99 per cent, of differentiation of barren, single- and multiple-bearing ewes of 98 per cent, and of determination of actual fetal numbers of 97 per cent can be achieved in practice at scanning rates of at least one ewe per minute. Some of the benefits to flock management and performance likely to result from the use of the technique are considered.

Three hundred pregnant beef cows between 35 and 125 days of gestation were scanned ultrasonically and their calving dates were predicted from measurements of fetal parts. The mean difference between the actual and predicted calving dates was 0.9 day with a standard deviation of 9.0 days. The accuracy and precision of the prediction of calving date were sufficient to be of benefit in the management of cows in late pregnancy and at calving.

Sixteen pregnant red deer hinds were scanned using real-time ultra sound at regular intervals during the first 150 days of pregnancy. In the early stages of pregnancy, an intra-rectal linear array transducer was used but later in pregnancy the hinds were scanned externally with a sector scanner. Pregnancy was determined from 30 days of gestation by intra-rectal scanning, and from 50 days by external scanning. With advancing age the size of the fetus increased, and linear regressions of size on age gave residual standard deviations of 0.508 days for head diameter and 0.506 days for trunk diameter. It is concluded that this technique can be used to determine pregnancy with a high degree of accuracy from 30 days of gestation and to predict calving date from fetal measurements within the range 1.5 cm to 7 cm for head diameter or 0.5 cm to 8 cm for trunk diameter, corresponding to a fetal age range of 35 to 150 days.

No abstract