Most cows do not need to be treated with antibiotics because they may interfere with the natural shedding process
Most cows shed the placental membranes within two to eight hours of calving. If it takes longer than that, infection could result.
Dr. Carling Matejka, a veterinarian at Fen Vet in Airdrie, Alta., says that if a cow takes longer than 24 hours to shed the placenta, it is considered retained.
“This is most common in cows that aborted or calved prematurely or had dystocia at calving or twins. It also may happen with milk fever at calving, due to low calcium, or with other nutritional disturbances, or cows with uterine infection prior to calving,” she says.
“We see retained placenta more often in dairy cows but we do see this every now and then in beef cows. Retained placenta also predisposes the cow to other infections, including mastitis — just too much for the immune system to handle at once. Dairy cows with retained placenta are also more likely to get a displaced abomasum (twisted gut).”
Anything that creates inflammation in the uterus at calving causes edema around the “buttons” (caruncles) on the uterine lining where the placenta’s cotyledons attach. The edema interferes with the normal separation after calving that allows the placenta to detach from the uterus.
“The edema does not allow the normal enzymes to come in there and does not allow the immune system to work on those areas and degrade those attachments,” says Matejka.
“Thus the edema persists and the attachments stay locked on until infection degrades them.”
Usually it’s obvious when a cow has a retained placenta because the membranes are protruding, but sometimes they break off and leave small pieces within the uterus that cause infection.
“The only sign in those cases might be foul-smelling discharge from the cow,” she says.
Most cows with retained placenta are not sick. The infection is localized in the uterus.
“If the cow is bright, alert, eating and drinking normally, still nursing her calf, we usually don’t worry about those membranes hanging out. The best thing to do for that cow is nothing. The best treatment is benign neglect.”
Generally a retained placenta is shed within two to 11 days. The immune system degrades the material so it can eventually fall away.
“We don’t want to give a cow antibiotics right away because it would interrupt that process,” Matejka says.
“The body is amazing and knows exactly what to do, and the uterus can clear itself of any residual infection. If we interfere by treating with antibiotics that are unnecessary, we may do more harm than good unless the cow is sick.
“If the cow is depressed, dull, lethargic, not wanting to eat, not mothering her calf, then we should treat with antibiotics. Take her temperature to see how severe the infection is. If she has a fever, we start with an antibiotic like penicillin or Bio-Mycin (oxytetracycline) injection.”
Matejka says she never recommends a uterine flush with antibiotics because there is no evidence that it is better than systemic antibiotics.
This is another reason veterinarians no longer recommend putting antibiotic boluses into the uterus after a difficult calving.
If the cow has a fever — anything over 39.5 C — Matejka prescribes a non-steroidal anti-inflammatory medication like Metacam. This will help reduce fever, ease pain and inflammation and make the cow more likely to eat and drink.
“Hopefully she will start eating and drinking again and we won’t have to tube her. If she is severely depressed, not eating or drinking, I tube her with electrolytes, glycol and water to supply the necessary fluid and energy.”
Matejka cautions against trying to pull out the membranes because it increases the risk of leaving pieces in the uterus that cause more problems. It is better to let gravity remove them slowly and gradually.
“Some producers ask if they should give oxytocin, but once a cow has calved she already has a lot of oxytocin in her system. Giving more won’t make much difference. Her uterus is already contracting and doing its job.
“If the placenta is going to be retained, it is not due to lack of contractions. It is because those attachments are still hooked up. Stimulating the uterus to contract more won’t make those let go,” says Matejka.
If there is more than the occasional retained placenta in a herd, producers should review the herd’s nutrition. Low calcium, selenium or vitamin E may be the cause. As well, a cow that is too thin or too fat is more likely to retain the placenta.
Selecting bulls for calving ease can also reduce the risk of retained placenta.