November 16, 2021
There are various options for diagnosing pregnancy in sheep. The cost/benefit analysis for doing this procedure depends on what you are going to do with the information. Your reasons for doing pregnancy diagnosis will also dictate which method you want to employ. In general, the earlier in pregnancy the diagnosis is made, the larger the risk of false positive results due to early embryonic loss. If avoiding false positive pregnancy diagnosis is essential to your production, it might be better to postpone diagnostic testing so ewes are closer to 60 days pregnant before testing.
Available diagnostic tests:
Pregnancy specific protein B (BioPRYN)
Ewes need to be at least 30 days pregnant. Overall accuracy for the test is 97% with 99% accuracy for a not pregnant diagnosis and 95% accuracy for a pregnant diagnosis. This test does not need to be done through a veterinarian, if you are able to pull a blood sample yourself. You will not be able to tell how many lambs a ewe is carrying. Pricing varies, starting at $2.40 per sample, depending on which lab you use.
Ewes can be identified as pregnant as early as 18 days bred. It is not a pregnancy specific hormone so ewes with abnormal cycles or cystic ovaries will have false positive results. This test needs to be done through your veterinarian and is a more expensive test.
A-mode Ultrasound Pregnancy detector:
This device sends out ultrasound waves and makes an audible tone when it encounters a fluid filled organ (pregnant uterus or full bladder). Draminski Pregnancy Detector (Priced at $396.50) recommends that ewes need to be at least 40 days pregnant with optimal results between 60 and 90 days of pregnancy. Pregtone (Priced at $494.95) recommends that ewes need to be 35-45 days pregnant if scanning the ewe in a sitting position or 60-65 days of pregnancy for a standing ewe. These devices are intended for use by farmers and can diagnose pregnancy with good accuracy if you follow the instructions. A full bladder can give false positive results.
Traditional ultrasound that generates an image that is displayed on a screen or goggles. Actual lambs can be seen and counted. Can be done via a rectal probe as early as 25 days or externally starting at 45 days. The experience and proficiency of the ultrasound technician is a big determinant of how useful the information will be. It is easier to be proficient at discerning a single lamb from multiples (2 or more) than it is to discern between twins and triplets. You need to be able to see all the lambs in one image to be able to count lambs so be sure to comply with the timing that your provider recommends if you want the best results. Prices are variable. In general, the price per ewe is much higher if you only test a few ewes as you have to pay for travel and setup regardless of how many ewes are scanned. Farmers can learn to perform ultrasound themselves, but there will be a learning curve. Ultrasound machines start at $1000 for entry level models and high-quality machines are much more expensive.
Leaving a ram with a marking harness in with the ewes at the end of breeding season can show you which ewes are still cycling and therefore not pregnant. This is very inexpensive to do but not 100% accurate as some rams will still try to breed pregnant ewes and ewes that are open because they are not cycling will appear bred. You will also have to contend with having a ram in the ewe flock for a longer time. If you do not cull the ewes that are bred by this ram it will extend your lambing season.
Standing behind a ewe, bend forwards and interlace your fingers just in front of her udder. Gently bounce her abdomen up and down a few times, you should be able to feel a lamb as a hard object bouncing back against your hands. This method only becomes accurate to use once ewes are over 100 days pregnant and there is a bit of a learning curve involved. This is pretty late in pregnancy to really be useful for culling open ewes.
During the last third of pregnancy you can start seeing udder enlargement and enlarged abdomens but you have to maintain a ewe through most of her pregnancy before these signs become obvious.
Scenarios where pregnancy testing is useful:
You plan on culling your open ewes:
- If you breed ewe lambs they can still be marketed as lamb if found to be open.
- Fall breeders can target the Christmas market with their opens rather than feeding open ewes through the winter.
- Save a few months of feed on not taking open ewes through a full gestation period.
- Blood tests or ultrasound will work. You only need open vs bred, no need to count fetuses.
You plan on feeding your ewes differently depending on the number of lambs they carry:
- Provide better feed to ewes carrying triplets or more in late gestation without having to increase nutrition for the whole ewe flock.
- Feed ewes carrying singles less so they do not end up too overweight in late pregnancy.
- B-mode ultrasound is the only test that will be able to give you the information that you need. Remember the skill level of your ultrasonographer is very important.
You do accelerated breeding and want to re-breed your open ewes ASAP
- BioPryn tests can give accurate results at 30 days bred. Rectal ultrasound can also give results as early as 25 days pregnant.
- Remember that you are likely to have some false positive results due to early embryonic death if you test very early in pregnancy.
Below are a few laboratories that perform BioPryn testing, I am sure there are a lot more than the ones that I listed. I have used DHI Cooperative for testing a few years ago and they provided a good service. Testing kits are also available from Valley Vet Supply, Walmart and other livestock product sellers.
Draminski Pregnancy Detector
By: EAPK Communications Committee
Isabel Richards, Gibraltar Farm