Most cows “clean” soon after calving, shedding the placental membranes within two to 12 hours. The uterus is shrinking up after being greatly stretched to accommodate the full-term fetus. Contractions (which help the placenta work loose from its attachments) actually continue for several days, although in decreasing frequency and intensity.
These contractions help the uterus return to normal pre-pregnancy size and aid the flushing of fluids and tissue debris. The cervix constricts, often very rapidly. Within 10 to 12 hours after a normal calving, after the placental membranes have usually been shed, it becomes difficult to insert a hand through the cervix if you were to then try to check the birth canal. Retained placenta is a common complication after calving; if the cow doesn’t shed those membranes within about 12 hours, it’s considered to be “retained.”
Factors that lead to a retained placenta can include anything that interferes with the “unbuttoning” of the cotyledons that attach the placenta to the uterus, or anything that hinders or limits uterine contractions, since these contractions help cause physical separation by distorting the shape of the placentomes (the attachment areas where the cotyledons of the placenta hook into the maternal caruncles on the uterus).
If a cow does not shed her placenta with 36 hours following birth of her calf, there’s a good chance she won’t shed it for a week to 10 days, since uterine contractions have ceased. After that point in time, the coming loose will depend more on the shrinking of the uterus and disintegration of the attachments.
Dr. Robert J. Callan, professor, and service head of Livestock Medicine and Surgery Section at Colorado State University, says the most common reason for retained placentas where he grew up in Oregon was selenium deficiency.
“You also see retained placentas in beef cattle due to dystocia and a hard calving,” says Callan. “Body condition of cows at calving can also be a factor in retained placenta, and may also lead to dystocia, since a cow that’s too thin or too fat may have more trouble calving.
“Cows that give birth to twins are also prone to retained placenta. It may be partly due to the fact that twins tend to come a little early. Cows that calve prematurely are more likely to retain the placenta,” says Callan.
Abortion or any cause of premature calving can lead to retained placenta. This would include pine needle abortion, as well as viral infections like BVD or IBR. One reason for retained placenta in some of these instances is that when the fetus dies, it doesn’t send the signal for maturation of the placental attachments so they can come loose when the cow goes into labour.
In earlier times, stockmen felt they needed to treat every cow that retained her placenta, and that these membranes should be removed. We now know that trying to remove the placenta may do more harm than good.
“Cows with retained placenta mainly just need time for the membrane to rot away from the attachments and come loose,” says Callan. It will always come loose after awhile (though it may take seven to 10 days), and the cow will usually be fine, unless it develops an infection that invades the uterine tissue (causing metritis) or the bloodstream (septicemia).
“So the main thing is to monitor the cow and make sure she is still eating and feeling good,” he says. “ If there’s any concern that she may be sick, check her body temperature. If it’s elevated (more than 103 F), treat her with an antibiotic. The choices may include penicillin, oxytetracycline, or ceftioluf (Naxcel or Excenel). These are all fairly effective for treating a septic retained placenta, in which a resultant metritis has led to septicemia.”
DON’T FORCE IT
Callan doesn’t recommend reaching into the uterus to manually remove the retained membranes. There’s always some risk of leaving pieces in there. Studies have also shown manual removal causes more damage to the uterine wall and compromises future fertility.
You can, however, grab hold of the external portion of the placenta that’s hanging out, and put gentle traction on it. If it does come out without tearing, this is fine. Just don’t pull very hard. If you feel it start to tear, stop. Try and pull it a little bit again the next day.
“You may be able to tease it out a little at a time,” says Callan. “Another thing I often do is take hold of those membranes while wearing a rectal palpation sleeve, and start pulling on it to see how much comes out. If it’s stuck and won’t come easily, I stop and while still holding the placenta I’ll invert the rectal sleeve over it.
“Now the portion of the placenta that’s outside the cow is inside the plastic sleeve (and not dragging around on the ground) and I’ll whip that around and tie it in a knot. This keeps it cleaner, and shortens it up so it won’t be inadvertently stepped on and torn, and keeps a little weight on it, for gravity to help ease it on out.”
If the cow does not develop a serious infection following the retained placenta, her uterus eventually clears the local infection and inflammation and she will rebreed successfully. Most cows have no further problems. †