Thursday, May 19, 2011

Birth Problems in Horses: Dealing with Dystocia

DIFFICULT PASSAGES: Dealing with Dystocia

The 11-month gestation period of horses is longer than that of most other mammals, but when the foal finally comes, the birth is surprisingly swift under normal circumstances, taking less than 30 minutes from the time the mare’s water breaks to complete foal out. This rapidity is necessary for wild horses, as a prolonged birth would leave both mare and foal extremely vulnerable to predators. While domestic mares giving birth don’t usually have to contend with predators, there are other dangers associated with the birthing process that owners of pregnant mares should be prepared to deal with. Dystocia, meaning difficult birth, can be serious or even life-threatening, and often requires human intervention. Ninety percent of the time, mares give birth without any difficulty, but understanding what can go wrong the other ten percent of the time can be a life saver.

Claire Card, DVM, Phd, diplomate ACT, is a Professor of Theriogenology (animal reproduction) at the Western College of Veterinary Medicine, with a special interest in Equine Reproduction. Having attended the births of countless foals, she says, “The risk of dystocia to the mare is that she will become injured by trying to foal with the foal in an abnormal location, as she may strain and strain until something ruptures or prolapses out like the uterus, bladder or rectum. She may also have her blood vessels injured or ruptured, resulting in hemorrhage, and she may go into shock and die. She will suffer a great deal of pain. Her uterus, cervix or birth canal may be permanently damaged. She may also be injured in the process of correcting the problem. Retained placentas and toxemia are common. The risk to the foal is death or debilitation due to oxygen starvation or acidemia. In many cases of dystocia, the placenta eventually detaches from the uterus and the foal dies by asphyxiation because that is its lifeline before birth.

Dr. Card explains that there are two main categories of dystocia: maternal, which are attributable to the mare, and fetal, which are attributable to the foal. Common maternal causes include a small pelvis, uterine torsion, exhaustion, placentitis, “red bag” or premature placental separation, and more rarely, twins. Common fetal causes include various malpositionings, developmental abnormalities, and oversized foals.

MALPOSITIONINGS

The most common cause of dystocia is malpositioning of the foal. Because of its long limbs and relatively large size, a foal must be in a specific position to facilitate its passage through the birth canal. Says Dr. Card, “It is very important that a foal attendant is alert and looking to see two feet and a nose coming out first from the mare’s vulva. One forelimb is usually about four to six inches ahead of the other in a normal delivery. Once the cannons are visible, the nose should be seen.” If this is not the case, the mare should be examined, as any deviation from this position is cause for concern and usually requires human intervention.

If a foal is malpositioned, labor typically does not progress, and no parts – or the wrong parts – are visible within 20 minutes of the water breaking. As Dr. Card explains, “In a normal birth, the limbs and nose are usually visible within five minutes of the water breaking. Once the water has broken, no more than 20 minutes should elapse before a mare is checked if the parts of the foal are not visible. The foal should be on the ground within 30 minutes of the water breaking.”

The most frequently seen malposition is the retention of a forelimb. In this case, one foot and the nose will appear from the mare’s vulva, but the other front leg is either folded up at the knee or extended backwards along the torso. Correcting this problem generally requires the attendant to push the foal back in while reaching inside the mare to get hold of the retained leg and gently bring it forward. This can be relatively simple, depending on how far back the foot is and how much room there is to work inside the mare. If the position of the retained limb is corrected before the mare is too exhausted to push anymore, the rest of the birth usually progresses quite quickly.

Other malpositionings include head back, poll lock (forehead on mare’s pelvis, nose pointing down), breech (rear end first, no legs coming), and transverse (all four legs and abdomen coming, or no legs and just the back coming). Says Dr. Card, “Most cases of malpositioning when the foal is normal are either chance events or the foal is a little too big. If the foal is a bit on the large side, the limbs may take up most of the space in the birth canal, and when the head tries to enter there is not enough room so it is turned sideways. Fetal oversize is rarely a serious problem, however, and experiments done many years ago crossing shetland mares with draft stallions via AI showed that the mares had the foals on their own without incident. Once in a while we do get a large foal that is too big to come out, but that is very unusual. If we can reposition the foal we can almost always get it out. With a posterior presentation (hind legs coming first), the solar (bottom) surface of the hooves face up. When the hooves of the foal face up, either the foal is backwards and the hind feet are coming out, or it is coming front end first but is upside down. Check to see if there is a nose or tail nearby.”

Abnormalities of the foal can also lead to malpositionings and dystocia. Foals with contracted tendons can be a problem because their legs simply do not bend the way they are supposed to. “When the problem is contracted tendons,” says Dr. Card, “repelling the foal sometimes allows us to get enough room to reposition the foal, or if it is severe, we usually have to anesthetize the mare to get the foal repositioned at the right angle to pull the foal.” Asked about other foal abnormalities that can cause dystocia, Dr. Card says, “Hypothyroid foals can cause dystocia due to their typically prolonged gestation (over 365 days), and they may be big or small or have badly contracted legs. Labors are not normal. Once in a while we get a ‘fetal monster’, such as hydrocephalus (huge head), or schistosomas, where the guts of the foal are not enclosed in a body wall, and the legs are abnormal.”

TWINS

Twins are a high-risk situation in horses, and it very unusual for a mare to successfully carry twins to full term. Usually, the mare will naturally abort or resorb one of the fetuses on her own, and if she doesn’t, a veterinarian will perform a procedure to “pinch” or crush one of the embryos to allow the other a reasonable chance at survival. When a twin pregnancy is undetected or allowed to continue, the mare commonly aborts both fetuses in mid to late gestation, leaving her at risk for a retained placenta. However, in rare instances where neither twin gets resorbed or aborted and the twin pregnancy was not dealt with by a veterinarian, a twin birth may result.

If it is not already known that the mare is carrying twins, there will usually be discernable clues during the birth. “Mares carrying twins usually develop a premature udder and foal at the beginning of the 11th month,” says Dr. Card. “Often the first twin foal is very small, which would lead you to suspect that there is another, especially if the mare is huge and she is foaling early. Another clue is that the two foals may try to come out at once, with one frontways and the other backwards. What you will often see in this instance is one limb facing up, and the other down, which you can tell by looking at the hooves. The way the leg bends tells you if you have a front or back leg. And, if you get two legs of impossible color combinations – like a bay and a palomino – you know you’ve got twins!”

The birth of twins is likely to be a difficult one and is best attended by a veterinarian. As Dr. Card explains, “The risk of complications is very high in a twin birth, which is why it is best to prevent such births whenever possible. General complications for the mare include: retained placenta (common due to foaling early and large placental mass), excess weight which can lead to issues with the abdominal wall muscle of the ventrolateral abdomen and prepubic tendon area, laminitis from excess weight, vaginal/vulvar injury/tearing/hematomas, and uterine infections due to manipulations to get the foals out. In terms of the foals, they may be stillborn, neurologically and/or physiologically abnormal, immunocompromised, and they may need intensive care to survive” Anyone assisting a twin birth should therefore have the knowledge, experience and tools to cope with these challenges, as well as the ability to sort out which parts belong to which foal, and the skill to manipulate malpositioned twins in extremely tight quarters without unnecessary damage to the mare.

Unfortunately, when a twin birth does occur, it is common for both foals to die due to inadequate development and nutrition in the womb. Veteran breeder Laurie Takoff of Kelowna, BC, however, attended one unusual case that had a happier ending. As she recalls, “Some folks called us early in Spring because their mare was foaling out about 60 days early. We rushed over to the farm, but by the time we got there, we found this tiny, hairless creature about the size of a fawn struggling to stand. After trying to calm the frantic mare owner and helping to get the stall organized, we noticed a dark smelly mass along with the placenta in a corner. It turned out to be a dead twin foal, and as it looked quite decomposed, we surmised that the mare’s body was dumping the dead foal, and at the same time, its twin was born. Surprisingly, the live foal ended up surviving – not without a ton of help and serious attention – but it did survive.”

“RED BAG” (PREMATURE PLACENTAL SEPARATION)

Premature separation of the placenta is commonly called “red bag” because it presents as a red membrane bulging out through the mare’s vulva. The placenta has two main parts: The outer membrane, called the chorioallantois (CA), and the inner membrane, called the amnion, which is the opaque sac that the foal is in. The CA attaches to both the uterus and the amnion, and normally stays attached to the uterus until after the birth of the foal, at which time the CA is expelled. When the CA detaches too early, red bag occurs.

As Dr. Card explains, “In a red bag birth, the cervix continues to dilate and the detached red CA membrane that should be attached to the uterus passes into the vagina. Contractions of the uterus allow more and more separation to occur, and finally enough separates so that the placenta bulges out through the vulva. When this happens, you do not see the water break. Normally, the CA breaks open at the cervix and the allantoic fluid is released. When it does not break, you may see movement in the mare’s vagina and movement of the vulva without fluid coming before the CA membrane is seen. The movement is the foal’s legs inside the membrane and it struggles due to asphyxia. Then the red CA with the cervical star on it bulges out. The star is white because it is the portion of the placenta that was up against the cervix, so no red villi form on it. Placental villi only form when the placenta is in contact with the uterus. The CA feels like a sac of fluid, and if you press hard on it you will usually be able to feel the foal’s parts inside the sac. Immediate intervention is required because the CA membrane normally provides the foal with oxygen during delivery, but it can’t do that if it is detached. If the foal is deprived of oxygen it may perish or have abnormal behaviour, what we call a maladjusted or ‘dummy’ foal’.”

Intervention in cases of red bag involves cutting the placenta open and getting the foal out as quickly as possible to allow it to start breathing. Care must be taken not to cut the foal or the mare, but if you are careful and expeditious, the foal can often be saved, even by someone with little experience. Of course, if the foal is malpositioned, which is not uncommon in red bag deliveries, it will require a more experienced hand to right the situation in a timely manner.

The causes of red bag vary, but in most cases, the cause is never known. “We know that older mares are predisposed to the condition,” says Dr. Card, “and older mares are considered higher risk pregnancies and deliveries in general, just as older women are. Infections of the placenta (placentitis) that cause it to thicken or toughen are another cause, and the infection may spread into the foal so it is too sick to get into the right position to be born. Exposure to the toxic endophyte products found in some fescue grass and hay are associated with the problem because they massively thicken the placenta.” Unfortunately, a mare that has had one red bag delivery is more likely to have another, with some mares having them year after year.

WHAT YOU CAN DO

In these and other types of dystocia, the best case scenario is to have a veterinarian present, but in reality, it is sometimes not possible to get a vet out in time to save a struggling mare and/or her foal. If you are inexperienced with such situations, a knowledgeable friend or neighbor can be your greatest asset. As Dr. Card says, “I strongly encourage people to set up a phoning tree when they have a mare due to foal. Make sure they have someone who is knowledgeable available, and be prepared to transport the mare for help if needed.” She also encourages people to watch foaling videos so that they know what to look for, and recommends the use of some kind of foaling monitor or camera to help ensure that you will be alerted to and present at the birth. She cautions, however, that foaling monitors on the vulva may not help with red bag deliveries. “I advise people to use milk strip tests because they are a quick and easy way to determine which three days they need to check their mares very closely. The milk strips detect ion changes in the prefoaling mammary secretion (calcium and magnesium increase) that are a sign foaling is impending. If you catch your mare sweating behind the elbows, restless, dripping or streaming milk, stand by.”

Laurie Takoff recommends that people get as much education as possible to prepare them for what can happen. “Many vet clinics offer foaling clinics or mare care and foaling classes, and if you’re very lucky you might live near a college or university that offers weekend courses. I highly recommend these! Most veterinarians have favourite pre- and post-foaling mare care literature and many of them offer to put together kits to help new mare owners be prepared. Seeking the advice and knowledge of experienced mare owners and breeders can also prove quite fruitful.”

It is important to remember that while intervention is sometimes necessary in a foaling, an inexperienced person can cause serious harm to both mare and foal by doing the wrong thing, or even by doing the right thing but at the wrong time or in the wrong way. As Takoff says, “I’ve seen and heard all kinds of problems over the years, and unless you know what to do, then getting in there to ‘help’ is often times just as damaging as doing nothing. Pulling the foal out can cause damage, and while some folks try to get the mare up to walk her, in many cases that can cause problems too. Unfortunately, waiting for the vet can be a death ticket, so sometimes all you can do is pray.”

Ultimately, if you are located in an area where experienced help is not readily available and your vet is more than a few minutes away, you may want to consider boarding your pregnant mare at a clinic or other facility that offers qualified, specialized care. While it may cost you a few hundred dollars, the peace of mind of knowing that your mare and foal will be in good hands should a problem present itself is well worth it.