Most of us, as horse owners, try to be present at the birth of our foals. All too often, however, we arrive after the little one is here. We arrive to find the little guy nursing while the placenta is still dangling about the mare's hocks. The last stage of parturition is the passing of the placenta. It is very important to monitor this stage closely, as any complication here may also be life-threatening to the mare.
Ideally, the placenta should be completely expelled through the vagina within three hours of delivery of the foal. If the placenta does not pass completely within eight hours, then a life-threatening condition known as Metritis-Laminitis-Toxemia Syndrome may rapidly develop.
After foaling, the uterus goes through a process known as uterine involution. It is during this process that the placenta separates from the uterus and is expelled. If this process is delayed, the placenta is often retained. If the placenta is retained longer than five hours, bacteria will begin to multiply rapidly and the placenta will act like a wick, allowing the bacteria to rapidly invade the uterus. A fetid fluid will then accumulate in the uterus, infecting the horse systemically through the bloodstream.
Within 24 hours, the mare will develop a fever and quit eating. She will appear depressed. Her mucus membrane will become congested, turning purplish or muddy in appearance. She will begin to act sore in her front feet, showing the first signs of acute laminitis or founder. At this point, treatment becomes difficult, with the possibility of the mare sloughing her hooves completely. If the disease continues to progress, the mare will die or be in such severe pain that she will have to be euthanized.
If your mare does not pass the placenta immediately upon foaling, don’t panic. It is common for a mare not to pass the placenta until after the foal nurses. The act of nursing will stimulate a natural release of the hormone oxytocin in the mare
Oxytocin plays a role in causing the uterine involution and passing of the placenta. It is very important that you do not attempt to manually pull the placenta out. If the placenta is attached, pulling will only cause more serious complications. If the mare is stepping on the hanging portion of the placenta, it can be knotted up to hang at the level of the hocks. The weight of the hanging placenta is enough pressure to help with passage. Any more tension could cause the placenta to tear, leaving a piece of it inside the uterus to rot and cause uterine infection. If the placenta has not passed within three hours, call your veterinarian. Most often the problem is treated with oxytocin given by injection to the mare. If the placenta is passed within five hours, then no other treatment may be necessary. If the placenta passage takes over five hours, systemic broad-spectrum antibiotics should be started. Banamine may also be given to help prevent the occurrence of laminitis in your mare.
Lavaging, or washing out, the uterus with saline and infusing with antibiotics is helpful in cleaning out the uterus to allow for the optimum chance for rebreeding in 30 days. Typically, if the placenta was retained longer than five hours or significant contamination occurred, the mare is usually not rebred on foal heat, but held off until the next heat cycle.
If you suspect a retained placenta, remember not to try to pull it manually, but call your veterinarian. If the placenta does pass, then spread it out and examine it to make sure it is complete and that it is not missing a piece (such as the tip of one horn). If you are unsure, save the placenta from your foal for your equine veterinarian to examine.