These three adjectives accurately describe retained placenta (RP) in dairy cows. Farmers have probably been dealing with RP since farmers started milking cows. Retained placentas are pretty hard to ignore, especially if you are the poor fellow who has to milk the cow for the next three days, and especially if you milk in a tiestall or stanchion barn. We all know how effectively a quick flick of the tail can be to transfer that RP right into one’s face. Since RPs are so hard to ignore, we humans have been trying to do something about them for a long time too. We try to prevent them. We try to treat them. Do they matter? Yes, they do matter. Cows with RP typically have decreased conception and pregnancy rates, and increased days open. RP also increases the risk of metritis, endometritis, ketosis and mastitis. Of course, these diseases can reduce milk production or increase the rate of culling. By itself, RP does not normally make a cow ill, but we all know how quickly a cow with RP can become a sick cow with metritis.
Can we prevent RPs? Quite a bit of attention has been given to preventing RP for a lot of years. Nutritional interventions like increasing vitamin E or selenium levels have been tried, or increasing metabolizable protein in the diet, but with inconsistent results. Reducing subclinical and clinical hypocalcemia has been recommended, but the role of calcium in placental separation is still unclear. Twinning is a risk factor, so herds that have reduced twinning may have made some success in reducing RP rates. Dystocia is another significant risk for RP, so use of calving ease bulls in some animals may also have reduced rates of RP in some herds. But the bottom line in terms of prevention is that no specific intervention has ever been definitively identified as a way to reduce the rate of RP. We have maintained a data set in our practice with a variety of parameters for our clients since at least 2004. In that data, the average rate of RP was 8.1% of calvings in 2004, and only 2.6% in 2021. The RP rate has shown a very steady continuous decline for at least 17 years. Since we cannot identify any specific intervention to decrease the rate of RP, how did this happen? Part of the reason is that twinning rates and stillbirth rates have declined from 7.1% and 9.4% to 3.2% and 4.0%, respectively, and both conditions are risk factors for RP. However the main reason is most likely that our clients just do a much better job with dry and prefresh cow management, thus preventing a whole lot of periparturient disease, including RP. That means fewer cases of milk fever, metritis, dystocia, ketosis, mastitis and displaced abomasum. By doing this, rates of RP dropped as well. So, perhaps good overall management is kind of a vaccine to prevent RP.
How should we treat RP? Well, of course the obvious thing to do is just go in there and pull the darn thing out. Just like cutting off a problem during surgery, once it is gone, it is gone. Since RP is so obvious, farmers have been manually removing placentas for at least decades, and probably centuries. However, scientific studies have consistently failed to show any appreciable benefit to the cow by removing the placenta. This means no benefit to the health or production of the cow, and no improvement in reproductive parameters either. At best, manual removal is neutral for the cow. However manual removal can result in damage to the lining of the uterus, more frequent, prolonged and severe uterine infections, and an increased length of time until the cow forms a functioning corpus luteum. Thus, manual removal is not recommended. What about intrauterine antibiotics or intrauterine disinfectants? Antibiotics have not been shown to reduce negative outcomes associated with RP. Nor have disinfectants, whether in pill or liquid form. Antibiotics, including ceftiofur and ampicillin, have been shown to be effective in treating metritis when given parenterally, however. What about hormones? Oxytocin and prostaglandins have been studied, and with the exception of one long-acting prostaglandin, which has not been available in this country for several decades, nothing has shown any benefit. So really, there are no recommended treatments for RP, unless the cow has metritis, in which case parenteral antibiotics can be administered. So, in simple terms, do not put anything in there, nor take anything out. Leave it alone. Treat the cow if she gets sick, or perhaps if you think she will get sick.
The long story of retained placenta is both a success and a failure. It is a success since we have very significantly reduced the rate of RP in dairy cattle. It is a failure in that no treatment, in spite of a lot of trying, manages to improve outcomes. Information for this article came from, Beagley, et. al,“Physiology and Treatment of Retained Fetal Membranes in Cattle, Journal of Veterinary Internal Medicine, 2010.
Bennett is one of four dairy veterinarians at Northern Valley Dairy Production Medicine Center in Plainview, Minnesota. He also consults on dairy farms in other states. He and his wife, Pam, have four children. Jim can be reached at bennettnvac@gmail.com with comments or questions.