Ultrasound Pregnancy Testing For Sheep
We decided to take the plunge and purchase an ultrasound machine to be able to do our own pregnancy testing this year. We have used Biopryn blood testing in the past and feel that it works well but now that we are lambing 150 ewes we decided that it was time to explore other options. Biopryn tests are $2.40 per ewe so when adding in postage and supplies we would spend about $400 per year. We saw $1 000 ultrasound machines advertised on E-bay and decided to take a chance on one of them.
When researching ultrasound machines there are the really good, expensive machines that veterinarians use but at $10 000 plus that did not seem to be a viable option. You get what you pay for and we realized that we would be giving up quality at such a low price point but would this machine be adequate for what we want to do with it? After checking all our bred ewes with it I will give it a thumbs up.
We purchased a new CMS600P2VET machine with a 3.5MHz probe from MedShop4U on E-bay for $999 and went to work. They do offer a choice of probes for this machine and the 3.5MHz seems to be the best for our intended use. They have free shipping and the machine arrived in good condition less than a week after ordering it. The manual is obviously translated into English and makes for entertaining reading. You do have to install the battery, but it just involves unscrewing a few screws, inserting the battery and replacing the screws. Just plug in the probe, switch on the machine and you are ready to go.
You will need ultrasound gel otherwise you will not see anything. You also need to have the screen shaded from light otherwise it is really hard to see what you are looking at. We will build a little enclosure for the machine for next year but just used a box on top of a bucket to put the machine in this year.
To be able to see inside the ewe you need a hairless area to put the probe on. Sheep have a naturally hairless area to the side and in front of their udders as you can see in the picture (the blue stuff is ultrasound gel). The picture is a ewe lamb so obviously an adult ewe will have more udder tissue but still hairless skin in the same area. We scanned the ewes and ewe lambs while standing in our chute, just place the probe (with a nice glob of ultrasound gel applied) on the hairless area on the right side of the ewe and aim towards her opposite hip. Our ewes and ewe lambs were at 67 to 87 days of pregnancy when scanned. They do recommend taking ewes off feed for 24 hours before scanning but we did not do that. I do think that there are a few where I would have been able to see better if they were emptier. I found it really easy to see who is pregnant, committing to who is not pregnant harder though and takes longer. I did end up re-doing a few that I was not sure about a few days later.
So, what do you look for? The easiest thing to see is cotyledons, they can be round or c-shaped depending on the angle that you are looking from. When you see them you can call her pregnant but I like to see the fetus/es too. In the picture below the little round balls with black in between them are cotyledons, the c-shaped one is also a cotyledon you are just seeing it from a different angle. The black is allantoic fluid.
Below are two photos of the same fetus seen from the side, you can see the spine in the first image in the second picture you can see the spine and the breast bone, you can also see some cotelydons above the spine.
The other fetal part that is easy to see is the head. You are looking down on the scull of the fetus from the top. The bones are bright white.
All the ultrasound images above were produced by the machine. I recorded video and was planning to post video but the data is stored in a proprietary format which could not easily be converted to a web friendly format. These are frames from videos.
As far as counting lambs, ideally you look for multiples of the same body part (head, spine, body) in the same screen. If you move the probe around you can see the same fetus from multiple angles and over estimate how many you have.
Conclusion: I like this machine for the purpose of calling ewes pregnant. My technique for counting fetuses needs some help but I noted what I think and in April we will see how I did. I think it helps that we had a lot of ewes to look at as it gets faster and easier the more you look at.