Foaling Protocols II
Vaughn W. Henry
What are the signs of approaching parturition and when does the manager actively get involved? Indeed, should the manager get involved? There are many other photo slides available elsewhere (see the main site for added foaling links) that describe typical activities and manager preparations, but there are still quite a few items that have continued to create confusion for horse breeders.
Generally, mares experience a 340 day gestation period, although there are many seasonal and breed differences, fetal influences and individual variations. As the mare approaches foaling, her abdomen distends, the muscles over the tailhead and croup will soften and sink, her vulva lengthens and softens and her udder begins to fill with milk. Her nipples may, and not all mares do, produce a substance that hangs from the end of the teats like dripping candle wax (that's why horse owners refer to it as wax) anywhere from a few hours to a few days before foaling. From an evolutionary perspective, mares generally foal late in the night or early morning hours, a behavior that allows for better survival of both mare and newborn foal. However, these late night foalings wreak havoc on a farm manager's daily schedule, so it's important to recognize when the expectant mare means business. Basically, that means learning to recognize symptoms typical of an uncomfortable horse. The foaling mare becomes more restless as she circles in the stall, rising from her laterally reclined position and rolling up on her sternum, getting up and down frequently, elevating her tail, sweating, looking back at her abdomen, her rectal temperature may rise and vaginal mucosa may redden.
The process of foaling is usually divided into three primary stages, with the preparatory phase being about two or three hours in length. This activity allows the mare to position the foal for a smooth delivery. Uterine contractions start at the oviductal end of the uterus and proceed towards the cervix. The reddish velvety textured allanto-chorionic membranes are forced against the cervix, and this pressure dilates the opening. These chorionic membranes rupture and release two or more gallons of fluid, much of it fetal urine that suspended the foal and the amnion during pregnancy. Some breeders refer to this process as "breaking water" and it signals the start of serious foaling activity. Continued uterine contractions now force the white, smooth textured amnion against the cervix further wedging it open. These contractions position the foal with head and extended neck resting on the two forelegs. The one foreleg is extended six to eight inches in front of the other, narrowing the foal's shoulder, to ease passage of the widest part of the foal through the mare's pelvis. If corrections to the foal's position need to be made, this is usually the best time to recognize and correct minor positioning problems. Severe problems occur quickly and prompt veterinary assistance is required before labor proceeds further. Cervical response to pressure causes oxytocin release which causes further uterine contractions, moving the foal's feet and nose up through the pelvis and the amnion may rupture as the foal's feet pass through the cervix.
Phase two is the fetal expulsion stage that usually is completed within 15 minutes. Mares foal quickly and when there are problems, there's little time to react. Better to be prepared and consider what actions may need to be taken than to create a plan while problems are occurring. During phase two, the mare's abdominal muscles assist in the contractions and further force the foal into the pelvic opening. One leg precedes the other by six to eight inches and then the foal's nose rests about eight inches behind the hoof of the second leg. This position is optimal for reducing frontal cross-section of the foal and should be noted every time a mare starts heavy labor. The amnion usually ruptures as the foal's feet pass through the mare's vulva, and the amnionic fluid is released to lubricate the tract and allow the foal to pass with less friction. The toes of the foal's hooves should point upwards, otherwise the foal may be positioned upside down or it's a signal that there is an extended hind leg presentation, neither of which is desirable. Once the foal's shoulders pass the pelvis, the rest of the birth proceeds quickly with an occasional twist needed to get the foal's hips to pass easily. The mare's uterus continues to contract and these muscular actions drive the remaining blood in the chorion through the umbilical cord to the foal. This is one reason to not sever the umbilical cord too quickly, as a liter or more of fetal blood is being sent to the foal during these contractions. For managers with a desire to do diagnostic blood work immediately, the umbilical cord is an easily accessible source of blood and it's less upsetting to the mare and foal if there's no need to wrestle a foal to get a jugular vein sample. That extra blood is delivered to provide additional red blood cells, and it is often lost because owners are in a big hurry to cut the cord or they upset the mare enough so that she stands prematurely. It's far better to leave things alone and not get in a rush. The same advice can be said about providing traction to assist the mare in delivering the foal. Intervention by attending staff often causes more problems that it's worth. Excessive force and mechanical extractions may cause rib and internal injuries in the foal and lacerations, perforations and prolapse of the mare's tract. While it's assumed that about 4 percent of deliveries have some degree of difficulty, some farms experience many more complications that may be attributed to overly enthusiastic attendants.
Once the mare stands or the foal moves enough to sever the umbilical cord, and there is less bleeding if the cord is stretched and broken than if cut with a blade, a clean, six c.c. plastic syringe case makes a good vessel to dip the foal's navel with iodine and disinfect the umbilical opening. Make sure the foal is breathing properly and there is nothing medically wrong with the mare. If the environment does not require immediate intervention or complete drying of the foal, is generally better to leave mare and newborn foal alone for additional time and observe. Mares are less agitated when farm staff aren't fussing about and are more willing to remain down. By staying down, there is less chance that the mare will slip and step on the foal or placenta and it gives her a chance to take a well-deserved rest. When she rises, she can be held and the free end of the placenta can be tied up to her tail so it isn't dragged and shredded around the stall. Some mares become frightened of an object chasing them around the stall, so it's generally easier to just tie the free end up and leave the majority of the weight freely hanging to provide gentle traction and assist in the third stage of parturition.
The third phase is placental expulsion. After further uterine contractions, the villi that have attached the fetal membranes like Velcro® to the uterine endometrium begin to shrink and separate. Most tenacious at the oviductal end of the non-pregnant horn, the placenta separates slowly and is expelled within 15 minutes to three hours. The weight of the partially expelled placenta provides a gravity assist and if the mare somehow kicks or damages the trailing membranes enough that they tear, there may not be enough weight to encourage the final expulsion. Retained placental membranes are common when mares have had a difficult delivery or if there has been uterine infection, probably due to the localized inflammation in the tract. When membranes are retained too long, there is a potential for colic, serious founder and metritis. If retained, veterinary assistance may be required to either manually remove the placenta or use hormone and antibiotic therapy as a common tool to assist the mare in passing the placenta.
Since the placenta is the environment in which the foal developed for 11 months, it makes good sense to inspect it closely. Look for tears and missing pieces that would alert the attendant to a possible retention problem, also it may warn of potential infection and problems with the foal. For example, meconium staining is thought to signal foal asphyxia; and molds and bacteria sometimes leave bare portions of the placenta depriving the fetus or nourishment. Remember that the placenta has been turned "inside out" as it was expelled, and the side facing the foal during pregnancy is visible as it is spread out on the barn floor. Note the size and weight, most fall between 10 lbs. and 13 lbs., color and texture. Because both horns of the mare's uterus are involved in providing nourishment through the placenta, both sides will be apparent, but the pregnant horn will be much larger. An excessively heavy placenta is a sign that there may be inflammation or that it is so laden with fetal blood that weighs more than normal; in either case, it is a signal that the foal may have problems with neonatal adaptation and infections.
Mares have been foaling a long time and evolution has developed a quick process that usually goes off without great difficulty. Being prepared for the occasional problems and finding professional resources before problems occur makes good management sense. Spend some time working on your checklist of normal procedures and actions and work with your professional advisors to make plans for the rare problems.
Henry & Associates
©1998