Treatment of retained placentas
Keywords: equine, placenta, retained, Burn's, infertilityThe incidence of retained placenta in mares has been reported to lie between 2 and 11 % of all foalings in most breeds. In other breeds, especially Friesians and draft horses, it can be far higher. Unlike the situation in cattle, retained placenta in mares is a potentially life-threatening disease.
If the placenta is still attached three or more hours after foaling, it should be considered retained. Although it has been stated (like the situation in cattle) that uterine atony does not contribute to retained placentas, the vast majority of retained placentas in mares are expelled after one or more injections of oxytocin; certainly not the case in cattle. In the author's experience, simple treatment with 10 iu of oxytocin i.m. every 30 minutes will dislodge the vast majority of retained placentas within five or six treatments. Treatment with continuous I.V. drips has been described but it is not clear if that method warrants its extra expense and inconvenience. As a nonapeptide, oxytocin is a small and stable molecule and is very rapidly absorbed after intramuscular injection. With little potential for abuse, it can be left with responsible horse owners together instructions for treating retained placentas. Placentas that are still retained after six treatments should probably receive intensive veterinary care.
A novel, effective, and apparently safe method of treating retained placenta in mares was described by Meijer et al in 2015. Briefly, this involves infusing water into any major umbilical blood vessel for several minutes until the placenta becomes dislodged. It has yet to become widely adopted.
An alternative treatment is to inflate the chorioallantois with fluid to loosen its attachment to the endometrium and presumably, to stimulate myometrial contraction. This is colloquially known as the Burns technique. The author has not found the Burn's technique to be reliable but has little experience with the procedure.
The collage of images below shows the typical appearance of a retained placenta and the application of the Burns technique in a mare. About 10 to 12 liters of saline are infused into the intact chorioallantois and the site of infusion is ligated with umbilical tape to retain the saline.
Image size: 1572 x 2046px
If the placenta has not been expelled within 30 minutes, the ligation is removed and the fluid is allowed to drain. Conventional care is then adopted. This care includes oxytocin, tetanus prophylaxis, antibiotics, non-steroidal anti-inflammatory drugs, and in the view of some, vasodilators to prevent laminitis.
Manual extraction of the placenta remains a contentious subject. In North America, the general belief is that the placenta should not be manually removed. Instead, a mare should be treated systemically (as described above) until her placenta has been expelled. This may take two or three days to occur. However, in Europe it is common to remove placentas manually if they have been retained for longer than three hours. Indeed in the Netherlands, it is actually considered to be malpractice if the placenta is not removed manually when it has been retained for longer than six hours post foaling. Interestingly, at least two peer reviewed studies have shown than manual removal of fetal membranes did not affect reproductive performance.
Selected references:
Canisso, I.F. et al 2013. A clinical approach to the diagnosis and treatment of retained fetal membranes with an emphasis placed on the critically ill mare. J.Equine.Vet Sci. 33: 570-579
Cuervo-Arango, J.et al. 2009 The Effect of manual removal of placenta immediately after foaling on subsequent fertility parameters in the mare. J. Equine.Vet Sci. 29:771-774
Gibbens, D. et al. 1972. The circulating levels of oxytocin following intravenous and intramuscular administration of syntometrine. British J. Ob.Gyn. 79:644-646
McKinnon, A.O. et al Eds. 2011, Equine reproduction. Second ed. Chapter 260. Wiley-Blackwell ISBN: 978-0-8138-1971-6
Meijer, M et al. 2015. How to use umbilical vessel water infusion to treat retained fetal membranes in mares. Proceedings AAEP 61:478-484
Paccamonti, D.L. et al 1999. PGFM response to exogenous oxytocin and determination of the half-life of oxytocin in nonpregnant mares. Equine Vet J. 31:285-288
Provencher, R. et al. 1998. Retained fetal membranes in the mare: A retrospective study
Can Vet J. 29: 903–910.
Rapacz, A. et al. 2012. Retained fetal membranes in heavy draft mares associated with histological abnormalities. J. Eq. Vet. Sci. 32: 38-44
Sevinga et al 2002. Reproductive performance of Friesian mares after retained placenta and manual removal of the placenta. Theriogenology.57: 923–930
Sevinga, M. et al 2002. Serum calcium and magnesium concentrations and the use of a calcium-magnesium borogluconate solution in the treatment of Friesian mares with retained placenta
Theriogenology 57: 941–947
