Understanding Pregnancy Loss in Dairy Herds

By Blake Jackson

Pregnancy loss in dairy herds remains one of the most frustrating challenges for producers. While it has always existed, modern diagnostic tools have made the extent of the issue more apparent.

In the past, pregnancy diagnosis was commonly performed by palpation between 35 and 45 days after insemination a stage when most early embryonic losses had already occurred. As a result, cows found open were typically assumed never to have conceived.

Today, advanced technologies such as ultrasound and chemical-based tests allow for much earlier pregnancy detection. This earlier diagnosis offers benefits, including the ability to identify open cows sooner and reinseminate them to reduce days open and improve profitability.

However, these advancements have also revealed an unsettling truth: many cows do conceive but lose their pregnancies during the early stages of embryonic development.

Research indicates that approximately 30% of pregnancies are lost before calving (O’Connor, 2006), with the majority occurring before day 28 of gestation. During this period, embryo development issues are often responsible for the losses.

Beyond the first month, further pregnancy failures can occur, with studies reporting rates between 3.2% and 42.7% (Pohler et al., 2016). After day 30, losses are more likely related to problems in placental formation or function.

Many diagnostic tests including BioPRYN, DG29, and IDEXX - detect glycoproteins produced by the placenta, which circulate in the cow’s bloodstream.

A recent study involving over 400 pregnant, lactating Holstein cows in Brazil used ultrasound at day 31 post-insemination to confirm pregnancies. Four weeks later, by day 59, 12% had lost their pregnancies, and an additional 7% lost them later, totaling a 19% loss rate.

Notably, cows that maintained their pregnancies showed higher levels of pregnancy-associated glycoproteins (PAG) at day 31. Researchers found that setting a minimum PAG threshold could predict future pregnancy losses with up to 95% accuracy.

This discovery could play an important role in herd management. Future diagnostics may identify “high-risk” pregnant cows requiring close monitoring. Detecting potential losses early would allow managers to take timely action, improving herd fertility and productivity.

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