With lambing season in full swing, the University of Wyoming Extension has published a new online resource for producers seeking to minimize pregnancy loss in their flocks.
Titled “Why Ewes Don’t Always Deliver What They Scan: Understanding Fetal Loss in Sheep,” the new publication synthesizes recent scientific studies to explain when, how, and why pregnancies may go awry, then outlines best practices for optimizing performance.
“A benchmark in profitable and sustainable sheep production systems is maximizing pounds of lamb weaned per ewe, and doing so requires attention to detail during every stage of breeding and pregnancy,” says Whit Stewart, UW Extension sheep specialist and associate professor of animal science. “This bulletin brings together timely knowledge and recent advances that help producers better understand how to support the ewe so she can successfully carry more lambs to full term.”
Co-authored by Stewart and Johnson County extension educator Micah Most, the new publication starts by identifying key milestones and pitfalls at each stage of pregnancy.
While a typical pregnancy lasts about 147 days, research suggests that most embryo losses occur before day 29, the authors report. Nutrition, stress, and environmental factors influence potential losses throughout the pregnancy, but are especially important during the first trimester.
“Because early losses are difficult to detect, maintaining optimal nutrition and stress-free conditions throughout pregnancy—especially during early development—is key to maximizing embryonic, fetal, and newborn lamb survival,” the publication states.
In sheep, pregnancy losses are often partial: it’s not unusual for a ewe to birth just one lamb even after an early scan indicated twins or triplets. Research shows that partial losses can be linked to specific sires and even the ratio of male and female fetuses in a single pregnancy.
Still, while some factors are outside a producer’s control, preventing undernutrition can help improve embryonic survival rates. Proper nutrition, disease prevention, ample forage resources, and a low-stress environment are all essential to increasing the odds of a healthy pregnancy.
The authors recommend working with a veterinarian to create a veterinary health plan that includes administering relevant vaccinations as well as practicing good hygiene, implementing quarantine measures as needed, and confirming diagnoses early.
Research-based strategies to support pregnancy health also include minimizing environmental and social stressors. In a state where shearing often occurs mid-gestation and weather conditions can be harsh, this is especially important, the authors note.
“Not every fertilized oocyte becomes a lamb on the ground,” they acknowledge. “But understanding why—whether it is early embryonic loss, infection-induced fetal loss, or the effects of nutrition and hormonal signaling—helps Wyoming producers make more informed management decisions.”
To read the full publication, visit https://bit.ly/sheep-fetal-loss. Contact Stewart at whit.stewart@uwyo.edu or Most at mmost@uwyo.edu with questions.
