As breeding season for spring calving approaches, cattle producers should understand the reasons a beef cow might not maintain a pregnancy that results in a healthy calf.
“Investigating the cause of conception failure and pregnancy losses can be a frustrating pursuit,” said University of Georgia veterinarian Dr. Lee Jones. “Sometimes a good outcome is identifying holes in the production system.”
When calving isn’t going well, the veterinarian will first determine whether the cow was preg checked and pregnant, and if she was, why she lost the pregnancy.
Cows lose pregnancies for a variety of reasons including management, mismanagement, environment and infectious agents. Preg check results can provide critical information, especially if a vet does the checks.
“Sometimes analyzing pregnancy data can give us insight into problems,” Jones said. “Then we can initiate prevention or diagnostics.”
He explained two categories of pregnancy loss: loss up to 45 days is considered early embryonic death, and loss between 45 days and term is stillborn. If the calf is born alive but fails to rise and nurse within a few hours, it’s considered stillborn.
Farmers want quick answers for calf losses, but answers aren’t usually straightforward. “We have to ask a lot of question,” said Jones. “What’s the herd health program, vaccinations, other health products, nutrition, other routine procedures, biosecurity and recent herd additions? Are there recent changes or events – have cattle been moved to pasture, changed feed or recently worked?”
Jones reviewed some of the infectious diseases that can result in fetal loss. “Leptospirosis can cause abortion at any stage of gestation,” he said. “Vaccines provide limited protection.” Lepto can be shed in semen and interferes with conception. It’s also zoonotic (transmissible to humans), so farmers should carefully handle any suspect tissue.
Neospora typically causes abortion mid to late gestation, but it can cause pregnancy loss at any point. “It comes from dog feces that contaminate feed,” he said. “If you’re buying recips, you’d probably rather not buy neospora-positive recips.”
Campylobacter can be difficult to detect and can cause late-term abortion or stillbirths. “It’s a sexually-transmitted disease from infected bulls and cows,” said Jones. “Diagnosis is finding the organism in fetal fluids.”
BVD can cause a variety of problems, including infertility in cows and bulls. It affects egg and sperm quality and can result in congenital defects, or calves may be born normal but have a BVD titer. When there’s infertility along with manifestations such as calf deformities, BVD should be on the checklist.
Anaplasmosis is becoming a major cause of bovine abortions and premature births. Calves are typically weak and don’t survive. A simple blood test can help diagnose anaplasmosis.
“One of the high-risk factors for anaplasmosis is a herd with recent additions, including virgin bulls,” said Jones. “I always recommend testing all new additions.”
Trichomoniasis is sexually transmitted. In most cases, the disease enters the herd via infected bulls, then resides in bulls’ and cows’ reproductive tracts. While “trich” is seen primarily in the Midwest and West, producers in the Northeast often purchase bulls from breeders throughout the U.S., so all bulls should be tested. Some cows carry the organism through pregnancy and remain infected after calving.
Mycotoxins in pasture forages, primarily tall fescue, can result in reduced milk production and fertility. The mycotoxin zearalenone interferes with estrogen and can cause reproductive issues. Diagnostics for exploring mycotoxins are expensive and not a priority in the early stages of investigating pregnancy loss.
Nailing down the causes of abortion can be frustrating. “Immediately following an abortion, especially after two or three, clients are committed to finding out the problem,” said Jones. “One abortion may not be worth the effort, but it might be the first of several in an outbreak.” He added that after one loss, farmers are more vigilant about observing cows for abortion storms.
To begin the diagnostic process, the vet will request a thorough history and try to determine whether the loss was truly an abortion or if the cow failed to calve due to not being pregnant.
“In the case of failure to calve, we check additional cows to see if more than one animal is affected,” said Jones. “We may have to palpate a few head and walk through the herd. In the case of an observed abortion with expelled fetus and/or membranes, we make sure the owner collects whatever material possible.”
Jones reminded farmers that some infectious agents are transmissible to humans and to take precautions to prevent disease transmission.
The veterinarian will look for clinical signs other than abortion, whether animals have experienced any other illness and determine the extent of the problem. “One case might be within normal,” said Jones. “Two to three percent of pregnancy loss between preg checking and calving may be within normal and not worth pursuing. It isn’t worth the farmer spending money on diagnostics with possibly no answer, but if several animals abort as a group, that’s something to pursue.”
Some infectious agents cause fetal death but the fetus isn’t aborted for days or weeks following exposure. In this case, the farmer should remove the affected animal from the herd and isolate her until there’s a diagnosis.
“While biocontainment might be a practical measure, we might not know who’s actually been exposed,” said Jones. “Animals that definitely aborted should be removed and housed separately because they could be contagious. One of the problems with a single [abortion] event is we can go in a variety of directions. Multiple abortions means multiple bad news, but it helps the veterinarian pattern the causes.”
Abortions may or may not be restricted to a single group or might be restricted within one group, such as first calf heifers, or new additions may be affected but not resident cows. Thin or aged cows may be a subgroup to consider, and newborns should be checked for congenital defects.
Farmers should note where the abortion occurred – in which pasture, pen or group, and whether there was recent movement from one pasture to another. Consider any differences in hay, feed or supplements in the group, and whether a weather event impacted the hay.
For a necropsy, the vet will want the placenta and fetus in the best possible condition. Ideally, the entire fetus will be available for submission to a diagnostic lab and should be refrigerated (but never frozen). Always handle an expelled fetus and/or fetal membranes with gloves and take precautions to not spread fetal materials.
“Everything that affects the fetus has to go through the placenta,” said Jones. “Even if it’s dirty, the placenta is valuable for analysis.” Blood samples will likely be needed, and possibly samples from non-infected animals for comparison.
Many abortion investigations don’t result in a definitive diagnosis. However, diagnostic results can help eliminate possible causes and provide the veterinarian with information that can help guide future measures.
