JEREMY HOWARD
Sheep Industry News Contributor
Determining the pregnancy status of a ewe is an important management practice, providing vital information to help move your flock forward. Determining if a ewe is open or pregnant helps you re-breed open ewes quickly or cull open ewes at the best financial time.
In a sheep operation, profitability is highly dependent on each ewe in the flock producing at least one lamb per year; open ewes do not bring in this profit, but still require significant inputs.
A ewe that does not breed has lost lifetime production value, will not produce milk in the parlor that year and decreases the overall profitability of the operation.
In fact, it takes the income of 2 to 3 productive ewes to pay for the maintenance of one retained open ewe that remains in the operation’s ongoing production cycle.
To prevent this cost to the flock, producers are encouraged to pregnancy check their ewes each breeding season. There are several methods to determine the pregnancy status of a ewe. Each method has its own positives and negatives associated with use.
One method is the monitoring of animals for the absence of heat. This technique can be learned by anyone and is inexpensive, but does require a lot of time and open ewes can be missed.
The ewes need to be monitored every 17- days from the date they were previously observed in standing heat. If the ewe returns to heat, she is not pregnant and will need to be re-bred or culled.
A second method is the use of an ultrasound to detect the pregnancy status of the ewe.
Ultrasounds can be expensive and require a trained technician or veterinarian to operate the machine. A benefit of using this technology is being able to determine pregnancy status of the ewe during the early stages of pregnancy, the ability to identify the number of lambs a ewe is carrying and the sex and viability of each lamb.
Through ultrasound, pregnancy status can be determined in the ewe as early as 35 days post-breeding until lambing.
If the ability to determine the number of lambs is desired, the optimum time to perform an ultrasound is from 35 to 90 days post-breeding.
A relatively new and efficient method for determining pregnancy status is blood pregnancy testing. Producers can collect a sample of blood from the ewe and send it to a laboratory to be analyzed.
Lab technicians use technology to detect a protein that is produced by the placenta during pregnancy.
If the protein is found in the sample, the ewe is confirmed pregnant; if the protein is not in the blood sample, the producer can work to re-breed the ewe.
Blood pregnancy testing can be cost-effective and an accurate alternative to palpation and ultrasound – and producers can collect the sample themselves. Tests are proven to be nearly 100 percent accurate when a ewe is determined to be open.
Using a new needle for each animal to avoid cross-contamination, a producer must draw at least 2 milliliters of blood per animal into a blood collection tube. The producer then numbers the test tubes sequentially and with the animal’s identification number and ships the samples with or without coolant – depending on the sampling company he or she is using – to a local laboratory for analysis. The laboratory tests the samples and reports results back to producers via email, fax, mail or phone.
In some cases – again depending on the company – blood samples can be used for multiple tests, including Ovine Progressive Pneumonia (OPP) and other serum-based diagnostic tests.
Conducting multiple tests at once provides the producer and his team with more information, allowing them to make more informed management decisions.
