Sheep Pregnancy Diagnosis 

One of the major limitations with progress in sheep farming has been the inability to know how many lambs each ewe is carrying in the advance of lambing.

Having access to this knowledge allows the farmer to control the nutrition of the pregnant ewe more effectively, resulting in a higher survival rate of the new born lambs, more efficient use of expensive feedstuffs and simpler management of the flock.

Of the techniques available for the diagnosis of pregnancy and the determination of foetal numbers of pregnant ewes, real time ultrasound is the most accurate and the most rapid. It has become the accepted technique for foetal number determination in most animal species.

Using this non-invasive technique, a beam of ultrasound is transmitted into the body of the ewe. Echoes returning from the different tissues in the path of the beam of ultrasound are converted into a live or "real-time" image on a small screen allowing the operator to see whether or not the ewe is pregnant. If she is pregnant, then the number of foetal lambs can be counted. Ultrasound frequencies used in "real-time" scanning cause no known harm to the ewe, her unborn lamb or the person using the Oviscan 6.

The skilled operator will be able to tell by about thirty days after mating whether or not the ewe is pregnant. Although at that stage, individual foetuses are too small to be confidently identified. The number of foetuses can be counted accurately from about forty five to a hundred days of pregnancy. After a hundred days it becomes more difficult to count numbers accurately and thus scanning flocks should normally take place between twelve and thirteen weeks after the beginning of mating.

A skilled operator will attain an accuracy of diagnosis of at least 99% with the number of lambs born being predicted to an accuracy of at least 98%. The technique of diagnosis is dependant on the ability of the hand to eye co-ordination as the probe is externally orientated on the belly of the sheep. This will be taught on training courses organised by BCF for every new operator.

Some work has also been done with ultrasound to try and improve the grading of lambs through studies of backfat measurement to help identify the most valuable market to send each lamb.