Mare Retains Afterbirth: Causes and Solutions
When a foal is born, breeders naturally pay close attention – especially to the foal: It must stand, drink, urinate, and defecate within a few hours. But don’t forget to monitor the mare as well! It’s very important that the afterbirth (placenta) is expelled within a few hours. Good nutrition for the mare significantly reduces the risk of retained placenta.
Minerals
Others
Vitamin E
Diseases
Breeding
13 June '25 • 4 min reading time
The placenta surrounds and nourishes the foal while it's in the womb. After the foal is born, the placenta also needs to be “born”. No remnants should be left behind in the uterus, as they can cause infection and fever. One to three hours after birth, the mare will usually experience new contractions to push out the placenta. Often, she’ll lie down again during this process. As an owner, you must check whether the entire placenta has been expelled – or ask the vet to do this when they examine the newborn foal.
A Series of Milestones
When a foal is born, every horse owner is naturally alert. Was the birth smooth? Is the foal breathing properly? Does it remain briefly attached to the umbilical cord to absorb extra blood? Does it stand up in time and begin nursing? Is it urinating and defecating? These are all critical steps in the first few hours after birth. Also, time the passing of the afterbirth: it usually detaches within 45 minutes to an hour, but should definitely be out within three hours. If not, call the vet. The vet will first administer oxytocin to stimulate contractions. In most cases, that’s sufficient. If not, the vet may have to manually peel off the placenta. Afterward, the mare will typically receive a uterine flush for one or more days to ensure nothing remains inside. You’ll also need to take her temperature multiple times daily to monitor for fever. Free movement is also essential to help any remaining debris leave the uterus.
Why is the Placenta Retained?
While not everything is fully understood, several causes of retained placenta have been identified. Some breeds, such as heavy draft horses and Friesians, are more commonly affected – in part due to higher levels of inbreeding. Research in Friesians shows that the rapid increase in inbreeding between 1980 and 2000 led to a higher incidence of retained placenta. Heavier and overweight animals are also at higher risk. Additionally, studies in draft horses found they have fewer oxytocin receptors in their uterus. As a result, the uterus is less responsive to contraction-inducing hormones and less likely to expel the placenta efficiently.
Minerals and Vitamins
Nutritional status also plays a crucial role in proper expulsion of the placenta. This is well documented in cattle. Researchers discovered a domino effect involving several biological mechanisms. It starts with metabolic stress caused by hormonal imbalances and nutrient deficiencies – often in protein, vitamins, minerals, or antioxidants. This stress affects the adrenal glands and hormone production, increasing cortisol levels. Cortisol weakens immunity and stimulates adrenaline production. Adrenaline activates specific receptors in the uterine wall that cause it to relax, making it more difficult to expel the placenta. That’s why proper nutrition during the last three months of pregnancy is vital – particularly adequate intake of protein, vitamins, and minerals.
Vitamin E Is Especially Important
Vitamin E (α-tocopherol) is known to support fertility and muscle health. A mare with sufficient vitamin E is more likely to conceive successfully. In cattle, vitamin E supplementation has been shown to reduce miscarriage and stillbirth rates. Cows given vitamin E were 22% more likely to become pregnant from the same insemination. Vitamin E, often combined with the mineral selenium, also acts as a powerful antioxidant. Because birth causes oxidative stress and releases toxins in the body, antioxidants help speed up recovery. Supplemented cows also had lower cortisol and fewer harmful fatty acids in their blood during delivery – and retained the placenta less frequently. In short: all vitamins and minerals matter, but vitamin E – especially with added antioxidants – is particularly crucial!
Bronnen:
Sevinga M, Vrijenhoek T, Hesselinks JW, Barkema HW, Groen AF. Effect of inbreeding on the incidence of retained placenta in Friesian horses. Journal of Animal Science. 2004 Apr;82(4):982-986. DOI: 10.2527/2004.824982x. PMID: 15080317.
Pontes GC, Monteiro PL Jr, Prata AB, Guardieiro MM, Pinto DA, Fernandes GO, Wiltbank MC, Santos JE, Sartori R. Effect of injectable vitamin E on incidence of retained fetal membranes and reproductive performance of dairy cows. J Dairy Sci. 2015 Apr;98(4):2437-49. doi: 10.3168/jds.2014-8886. Epub 2015 Feb 11. PMID: 25682134.
Rapacz-Leonard A, Raś A, Całka J, Janowski TE. Expression of oxytocin receptors is greatly reduced in the placenta of heavy mares with retained fetal membranes due to secondary uterine atony. Equine Vet J. 2015 Sep;47(5):623-6. doi: 10.1111/evj.12426. Epub 2015 Apr 27. PMID: 25640716.
Xiao J, Khan MZ, Ma Y, Alugongo GM, Ma J, Chen T, Khan A, Cao Z. The Antioxidant Properties of Selenium and Vitamin E; Their Role in Periparturient Dairy Cattle Health Regulation. Antioxidants (Basel). 2021 Sep 29;10(10):1555. doi: 10.3390/antiox10101555. PMID: 34679690; PMCID: PMC8532922.
Ryszard Mordak, Józef Nicpoń, Josef Illek. Metabolic and mineral conditions of retained placenta in highly productive dairy cows: pathogenesis, diagnostics and prevention – a review. 2017. ACTA. VET Brno. https://actavet.vfu.cz/86/3/0239/
