Human error, such as giving a pregnant cow drugs that might cause abortion, can be another factor. Treating a cow with dexamethasone or some other steroidal anti-inflammatory, for instance, can cause pregnancy loss, especially in the last trimester.

Accidental administration of drugs such as prostaglandin F2a (Lutalyse®) or dexamethasone (cortisol) may cause abortion. “If a cow needs treatment with anti-inflammatories, producers should consult with a veterinarian about choice of drugs, dose and frequency,” Kasimanickam says.

“Any product, including vaccines, should be carefully studied before administration,” Tibary adds. “Read the label and check with your veterinarian to see if it’s contraindicated in a certain stage of pregnancy.” 

Sidebar: Shipping stress

Transport stress can be a factor in lost pregnancies, especially in the first month after being bred. Shipping cattle at 1-4 days after artificial insemination (AI) is best, as the embryo is still in the oviduct and less likely to be affected by uterine changes, says Ram Kasimanickam, a DVM in Washington State University’s Department of Veterinary Clinical Sciences. It’s also safer after day 42 -- when the pregnancy is well established, the placenta is fully attached, and the fetus is less susceptible to any changes that might result from stress, Kasimanickam adds.

“Shipping at seven weeks after AI is usually considered safe, but pregnancy loss due to shipping has been reported up to 60 days after AI. Care should be taken to reduce stress when animals are transported; never overcrowd trucks or trailers, and handle cattle as gently and calmly as possible,” he advises.  

Sidebar: Nutritional stress

Nutrition – especially trace mineral deficiencies – has been linked to increased embryo loss in a herd. And poor preparation of heifers for breeding, or cows losing a lot of body condition just before or immediately after being bred, can result in nutritional stress.

“This change affects hormonal profiles. Nutritional stress can cause early or late pregnancy loss. Specific nutritional deficiency (such as certain trace minerals) can be a factor, even in a herd fed adequate energy and protein. The most important trace minerals affecting reproduction are selenium, copper and manganese,” says Ahmed Tibary, DVM and Washington State University professor of theriogenology.