Early detection of pregnancy and determining fetal numbers have economical benefits to sheep producers. The method to use for pregnancy diagnosis should be simple, accurate, rapid, inexpensive, practical and safe for both operators and animals.
Accurate pregnancy diagnosis can be achieved by progesterone and blood test assays, these blood tests are commonly called “PAG” tests. However, research shows there can be up to 20% false positives. The accuracy for determining between single and multiple fetuses is not that accurate or inexpensive.
Rectal abdominal palpation with a wand is a simple, cheap and quick method, however its accuracy for determining multiple pregnancies is low and it can cause abortion or rectal perforation.
Doppler technique requires great skill to achieve high accuracy for pregnancy diagnosis and prediction of fetal numbers. [On a side note; occasionally, producers that have experienced “Doppler machines” say they are very accurate and all of their ewes get pregnant. However, when using a fertile ram and having small numbers of ewes, having a near 100% pregnancy rate will most likely happen in a healthy flock.]
Radiography and Transabdominal B-mode Ultrasonography are able to accurately diagnose both pregnancy and fetal numbers.
However, Transabdominal B-mode Ultrasonography is cheaper and safer than radiography. It can also be able to detect the fetal viability.
The optimum time for using transabdominal Transabdominal B-mode Ultrasonography in sheep ranges from 25 to 110 days of gestation. The optimum time for detecting pregnancy is from 45 to 90 days of gestation. An advantage to using Transabdominal B-mode Ultrasonography is that accurate pregnancy can easily be accomplished, confirming fetus viability, determining actual fetal numbers, and staging pregnancies within a two day window.
28 Day Sheep Pregnancy. Image was taken with the CL3.8 curved linear transducer.
27 Day Sheep Pregnancy. Image taken with the Ibex Ultrasound and CL3.8 Curved Linear transducer.
45 Day Sheep Pregnancy. Image was taken with the Ibex ultrasound and CL3.8 curved linear transducer.
Sheep Cranium - Thorax w heart - Front leg 75 days plus w 3.5MHz Sector probe
Sheep Cranium & Cotyledons 75 days plus w 3.5MHz Sector probe
Sheep Preg ~ 40-45 days w 3.5MHz Sector Probe
Producers can make management decisions for their sheep based on the results of the pregnancy diagnosis using Transabdominal B-mode Ultrasonography. This will be discussed in future blogs.
Article submitted by: Gary Veserat MS, PAS*
* American Registry of Professional Animal Scientists