GESTION PRATIQUE DES DYSTOCIES DE LA JUMENT PRACTICAL MANAGEMENT OF EQUINE DYSTOCIA. Dietrich VOLKMANN

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1 Published in IVIS with the permission of the editor Close window to return to IVIS GESTION PRATIQUE DES DYSTOCIES DE LA JUMENT PRACTICAL MANAGEMENT OF EQUINE DYSTOCIA Dietrich VOLKMANN Department of Clinical Sciences - College of Veterinary Medicine East Rollins - University of Missouri - Columbia, MO Résumé : Des conseils pratiques sont proposés pour la gestion du poulinage de produits de valeur, en vue de sauver la vie du poulain. Le rôle du vétérinaire traitant est évalué, avec l accent sur la réduction rapide de la dystocie en élevage ou, alternativement, le référé vers un centre de soins spécialisés. Des approches différentes sont proposées, visant en priorité soit la survie du poulain, soit celle de la jument avec la préservation de sa carrière de reproductrice. Une infrastructure sophistiquée, une équipe de plusieurs cliniciens, un investissement considérable en coût et en main-d oeuvre (anesthésie générale, césarienne...) sont souvent nécessaires pour espérer un taux de survie optimal du poulain. En revanche, moins de personnes, un équipement moins sophistiqué et des efforts moins délicats et bien moins onéreux sont nécessaires pour la délivrance par voie naturelle ou par la fœtotomie de poulains morts, souvent réalisées sans anesthésie générale. Les principes conduisant à une exécution sûre des différentes interventions obstétriques sont présentés. Enfin, la prévention et le traitement des complications post-délivrance, fréquemment rencontrées chez la jument ayant souffert de dystocie, sont présentés. Mots clés : Mise bas, poulinage, fœtotomie, section césarienne, obstétrique Abstract: Practical advice is provided for the management of pregnant mares carrying valuable foals so that any possible obstetric interventions can be applied in time to save the foal s life. The role of the field veterinarian is discussed with emphasis on the rapid resolution of the dystocia on the farm or, alternatively, timely referral to a specialty center. Different approaches to the resolution of dystocia are proposed for cases that aim primarily at foal survival and for those that aim primarily at mare survival and the preservation of future breeding soundness. Sophisticated facilities, a team of several clinicians, much effort and considerable expense (including general anesthesia and cesarean section) are frequently required to ensure optimal foal survival rates. In contrast, fewer people, much simpler facilities, and much cheaper, less elaborate efforts are needed for the vaginal delivery of dead foals by manipulation and fetotomy, both of which can most often be performed without general anesthesia. Principles for the safe execution of all forms of obstetric interventions are presented. Finally, the prevention and treatment of post-delivery complications commonly encountered in mares that suffered dystocia are discussed. Key words: parturition, foaling, fetotomy, cesarean section, obstetrics

2 Introduction Several excellent reviews and retrospective studies on the clinical management of equine dystocias have been published in recent years (16, 2, 9, 19, 11, 12, 10, 8, 4, 13, 15). The author is impressed by the divergence in conclusions drawn from the experiences of others it is clear that the preferred approach to the management of equine dystocias depends very much on each institution s peculiar circumstances when they are faced with the challenge of resolving complications arising during the birth of a foal. It is abundantly clear that there is not just one correct approach that can be applied to all equine dystocia cases around the world. The focus of this presentation is not to review the published results of others, but to provide a guide for the resolution of equine dystocias, mostly derived from the author s personal experiences in several different settings. While the author is well trained in equine theriogenology and very familiar with the expectations and aspirations of the equine breeding industry, it was his training in bovine obstetrics that provided him with the means of developing what he believes to be a balanced and successful approach to the management of equine obstetrical cases. Around the world, the veterinary profession deals with many more bovine dystocias than equine dystocias, simply because there are more cattle in the world than horses and because cows suffer dystocia more often than mares. Exposure of the veterinarian to bovine obstetrics provides enormously valuable training and learning opportunities in fetotomy techniques. The equine client, however, has very different expectations of the veterinary profession than does the bovine client and many of the differences in our approaches to dystocia between these two species reflect differences in expectations rather than techniques. It is equally important to appreciate the profound differences between the bovine and equine species in relation to anesthesia (local or general), surgery and peripartal care. Most bovine dystocias are resolved on the farm by a single veterinarian with little or no assistance from trained helpers; a cesarean section on a mare is virtually unthinkable today without the availability of a well equipped equine hospital, at least three specialists (anesthetist, surgeon and neonatologist) and ample assistance from trained paraveterinary staff. The demands and expectations of the equine industry have lead to the ever increasing development of equine specialty hospitals and clinics, staffed with veterinarians who, through the nature of their learning careers, have had few opportunities to practice their obstetric skills. In contrast to bovine veterinary practice, the case load of the modern equine hospital includes a relatively small proportion of obstetric work, often leading to relative neglect of this small, but dramatic field of equine veterinary medicine in many dedicated equine care facilities. Choosing an appropriate emergency response Each horse breeder should develop an emergency response plan for the time when a mare requires obstetric assistance. A foal will rarely survive second stage labor for longer than one hour and even when superb neonatal care facilities are available, it is virtually unheard of that a foal delivered more than 2.5 h after the onset of second stage labor survives. It is thus essential that the breeder defines

3 his/her goal for the outcome of a dystocia well before the mare is expected to foal: If foal survival is at all important, the mare should foal under the care of an experienced foaling manager in a well equipped facility that offers 24 h surveillance and is located in close proximity to a sophisticated, tertiary care hospital for horses where all options for the resolution of a dystocia are available to deliver the foal within no more than h of the onset of second stage labor. In addition, a plan for the swift transportation of the parturient mare to the hospital at any time of day or night must be in place. Obviously, the owner must also be prepared to spend very large amounts of money on the veterinary interventions that may become necessary for the delivery and neonatal care of a live foal. For this approach to yield satisfactory outcomes in terms of foal survival it is not desirable to involve the services of an ambulatory veterinarian prior to referral to a hospital. The following data from a large referral hospital in Kentucky provide support for the approach as described above (4): Of 247 dystocia cases only 42% resulted in the delivery of live foals (with 29% surviving to discharge). The duration of second stage labor for foals delivered alive was 71.7 ± 34.3 min, while the same interval for foals delivered dead was only 14 min longer (85.3 ± 37.4 min). The interval from arrival at the hospital to the delivery of the foal (regardless of the method of delivery) was 23 ± 14.1 min for live foals and 24.8 ± 10.6 min for foals delivered dead. If, however, the value of the expected neonate does not warrant the high cost of, for example, a cesarean section, the owner needs to devise a plan for the veterinary care that is necessary for the survival of the mare in dystocia, with or without the preservation of her future breeding ability. Most such cases can be seen and treated very successfully on the farm by an ambulatory veterinarian who, in many cases, may even achieve the delivery of a live foal by the prompt correction of minor postural deviations. Should the initial veterinary interventions be unsuccessful, the loss of the foal must be anticipated, while the mare can still be transported to a tertiary care facility for the resolution of the dystocia by more advanced interventions such as fetotomy or assisted delivery under general anesthesia. In the author s opinion, there are very few dead foal equine dystocias where vaginal delivery (with or without partial or complete fetotomy) is impossible, provided the obstetric interventions are performed by a highly skilled obstetrician. In fact, when the unborn foal is already dead, a skillfully performed vaginal delivery must not only be seen as a cheaper intervention, but also a more desirable option than a cesarean section that is associated with more inherent risks for postdelivery complications. The initial examination Regardless of where the mare is or who examines her to determine the cause of her delayed delivery, the examination should always be preceded by the application of a tail wrap and cleansing of her perineum with soap and water. A vaginal examination should then be performed and the disposition of the fetus inside the mare should be determined as accurately as possible. This examination is

4 easiest to perform on the standing mare, but many foaling managers will perform it while the mare is recumbent. In fact, many experienced attendants will perform such a vaginal examination on every mare within a few minutes after the rupture of her allantochorion or when the duration of first stage labor fails to result in the rupture of her membranes, even before a dystocia is suspected. Minor postural corrections can then be undertaken (elbow lock, a front leg over the foal s head, minor rotation along the longitudinal axis, flexed head) and, when indicated the allantochorion can be ruptured manually (red bag delivery). Many attendants will leave the mare to foal on her own if the foal s disposition was found to be normal, while others will routinely assist the mare by pulling on the foal s front legs. The latter may contribute to an increased incidence of cervical trauma resulting from the premature forced extraction of the foal. In the author s opinion every foal whose allantochorion needed to be broken manually should be extracted immediately as it may already be severely compromised by the separation of its placenta. The aim of the initial examination (and possible intervention) must be to make a timely decision regarding the need for more advanced assistance. There is no need to waste time to assess whether or not the foal is still alive at this early stage it should just be assumed to be alive. Unless the examiner is very confident in his/her own ability to correct whatever abnormal disposition is diagnosed, help should be called immediately or arrangements for the transportation of the mare to a hospital should be initiated without any delay. While waiting for advanced help to arrive, the mare s abdominal contractions should be controlled as best as possible: she should not be allowed to lie down (walking her is best); if possible, an epidural anesthetic may be administered; passing a nasogastric tube into the trachea reportedly results in a significantly weaker abdominal press. In countries where it is available, clenbuterol ( mg total dose) should be administered intravenously to induce myometrial relaxation (4, 3). The secondary examination and care of the mare This examination should be performed by the obstetrician who is responsible for any advanced interventions. The mare should be placed in a stall or space where the delivery is to be performed (many advise to perform this examination inside an induction stall that has a non-slip floor and an overhead hoist) and her tail should be wrapped and the perineum washed again. If they have not yet received the drug on the farm, injectable clenbuterol (3) should be administered intravenously to all mares in dystocia as soon as they arrive at the clinic. Again, the foal s disposition should be determined with great accuracy and at this time, as some time may have passed since the onset of second stage labor, the foal should be examined for signs of life. The birth canal is also examined for the presence of significant swelling or lacerations and the degree of cervical dilation is assessed. In order to determine all the options for the delivery of the foal the owner should be asked whether or not he/she is prepared to pay the estimated cost of a cesarean section. It is crucial to acknowledge that it is not easy to confidently declare a foal to be dead by any means other than the absence of a heart beat.

5 In the author s opinion it is therefore wise to have a second person perform a transabdominal ultrasound examination on the mare in order to locate the fetal thorax and heart (the thorax and heart of the cranially presented foal are usually located near the mare s umbilicus and the examination should commence in this area.. Particularly when the aim is to deliver a live foal and all options for delivery are available, the following actions should all happen simultaneously: Vaginal examination by the obstetrician Placement of a jugular catheter and initiation of fluid therapy Preparation of the tail root for epidural anesthesia Transabdominal ultrasound examination to detect fetal heart Clipping of the abdominal wall for a possible cesarean section Preparation of the operating room for a cesarean section Drawing up of sedative and anesthetic drugs Setting up of a neonatal resuscitation station The list above implies that it requires many people to perform all of the actions that need to be taken in the shortest possible time. A comprehensive dystocia team will thus consist of an obstetrician, a surgeon, an anesthetist and a neonatologist. While the obstetrician performs an initial vaginal examination and performs whatever corrective manipulations may be possible, either the surgeon or the neonatologist can perform the ultrasound examination and the anesthetist can attend to the placement of a catheter, the initiation of intravenous fluid therapy and the assessment of the mare s clinical status. Additional people are needed to restrain the mare and to prepare the abdominal wall, the operating room and the neonatal care station. In order to be well prepared it is useful to have three or four previously set up carts stocked with medications and equipment necessary for: Obstetrics Anesthesia and fluid therapy Neonatology General care of the mare By the time the mare is ready for induction of anesthesia (about 10 min after arrival) the obstetrician will have made a decision regarding the best method for the delivery of the foal, the status of the foal (alive or dead) will be known, all members of the team will be assembled and ready for further action, and the owner will have decided how much money can be spent. Choosing the appropriate method of delivery 1. The foal is alive or possibly alive and a cesarean section is an option: In such cases it is wise to anesthetize the mare without delay unless the foal s disposition has already been so corrected that it can be extracted (if general anesthesia is decided upon, no time should be wasted on the administration of epidural anesthesia). The obstetrician will decide whether or not a vaginal delivery is still likely

6 after further vaginal manipulation of the foal while the mare is anesthetized. If so, the mare s hind legs are hoisted to about 1 m above floor level to provide more room for repulsion and manipulation of the foal in the caudal abdomen of the mare. At the same time the abdominal wall of the mare is scrubbed for surgery. No more than 10 min should be required for the correction of an abnormal fetal disposition (including shoulder, elbow or carpal flexures, lateral or ventral head deviations or various flexures of the hind legs in caudally presented foals). If the foal is ready for extraction the mare s hind end is lowered to floor level and the foal is extracted. If the foal s disposition could not be corrected within the allotted 10 min, or as soon as the obstetrician has decided that vaginal delivery is impossible or undesirable, the mare is moved into the operating room as rapidly as possible and a cesarean section is performed. 2. The foal is alive or possibly alive, but a cesarean section is either impossible or too expensive: Such cases are best kept in the standing position, heavily sedated with a combination of detomidine and butorphanol, an epidural anesthetic is administered in the first palpable joint of the tail [7-8 ml 2% lidocaine or a combination of xylazine and lidocaine or carbocaine (14)], the mare is placed on a slope facing downhill and every effort is made to correct the fetal disposition and extract the foal. If vaginal delivery is either impossible or not desirable for fear of excessive trauma to the birth canal, the anesthetized foal needs to be destroyed by exsanguination in utero and a fetotomy be performed while the mare is anesthetized. The rules of the AVMA clearly state that the destruction of a conscious animal by exsanguination is illegal, and since the foal cannot be rendered unconscious by any other means than the full anesthesia of the mare, this option is not available for the standing mare with a live fetus. This implies that the mare must then be anesthetized and, while she is down, a further effort at the correction of the foal s disposition can be made prior to the destruction of the foal. The extreme alternative is euthanasia of the mare. 3. The foal is dead and can be delivered by any method: In the author s opinion, the proportion of dead foal dystocias that cannot be resolved through a vaginal delivery by a highly skilled obstetrician is very small. Since the foal is already dead, much more time can be allowed for the delivery of the foal while the mare is still standing. The clinician is reminded that anesthesia, while very safe in most cases, is not entirely risk-free. This holds true for especially heavy horse breeds and for situations when the anesthetized mare cannot be laid on appropriate padding or when the anesthesia cannot be induced and maintained by appropriately trained staff. The author shares the opinion of some others who have concluded that a fetotomy is easier to perform on the standing mare than on the anesthetized mare (7, 19, 6). Others, however, routinely perform fetotomies on all mares after induction of general anesthesia (4, 15). It is the author s firm opinion that fetotomy is an elegant and enormously successful technique for the resolution of equine dystocia (7, 19, 5, 15, 6). Not only are the vast majority of abnormal fetal

7 presentations resolved after only one or two sections, but even complicated situations requiring complete fetotomies have been very rewarding. Mare mortality rates after fetotomy have been recorded to range from 5 to 45% (1, 19, 15, 4), but the author has been fortunate enough to not ever have lost a mare on which a fetotomy was performed by himself or by a less experienced clinician under his immediate supervision. The inadvertent trauma to the mare s birth canal, another complication commonly cited as a significant consequence to fetotomy, can be limited to a large extent by the skillful and appropriate use of the fetotomy equipment. When a partial fetotomy is used to remove the offending extremity of the foal, but the foal is still not easily extracted, the author suggests further dismemberment of the foal by fetotomy rather than the forceful extraction of the foal. While a detailed description of the techniques for fetotomy (7, 2, 6) falls well outside the scope of this presentation, a few general guidelines are: All experts on this subject agree that, without substantial training and experience, fetotomy is very challenging and often results in excessive trauma to the mare s reproductive tract (uterine, cervical and/or vaginal lacerations). The obstetrician needs to be well versed in the appropriate use of the fetatome and accessory equipment. Ample lubrication is necessary to prevent trauma to and irritation of the birth canal during the removal of even small transected body parts. For fetotomies on foals of large mares, particularly draft horse mares, it is often helpful for the obstetrician to have long, slender arms. Supportive therapy to the mare should not be postponed until after the delivery of the foal, but should be administered prior to starting the fetotomy and maintained during the procedure if necessary. Supportive therapy routinely applied by the author includes: o Heavy sedation, o Epidural anesthesia, o Intravenous fluid therapy, o Intravenous, broad spectrum antimicrobial therapy (gentamicin and potassium penicillin), and o Intravenous flunixin meglumine The obstetrician should assure that his/her manipulations are performed inside the allantoic cavity of the mare. The allantoic cavity can be distended by the infusion of large volumes of dilute lubricant or even water. The use of large volumes of lubricant often results in its escape from the vulva during the fetotomy and can render the floor behind the mare very slippery its regular removal from this area by an assistant is important to provide secure footing for the obstetrician and those assisting in the fetotomy.

8 While rarely encountered, there are some dystocia cases that are best resolved by cesarean section even when the foal is already dead. Examples are: The detection of pre-existing lacerations to the birth canal or uterus The failure to accurately diagnose the exact disposition of the foal. The removal of any body part by fetotomy just because it could be reached and transected is an irrational, and very frequently counterproductive, approach. Inadequate space in the birth canal, even after all measures have been taken to increase space available for fetal manipulations. Some severely deformed fetuses, often with severely malformed and/or contracted leg joints (20, 18). The inability of the obstetrician to reach deep enough into the uterus to introduce the fetotomy wire around the targeted body part (most often encountered in transversely presented fetuses). 4. The foal is dead and the mare is suffering from some concurrent disease: While it is very rare that a mare presents in dystocia while she is also suffering from some other disease, these cases require careful deliberation between involved colleagues and between them and the owner(s) in order to choose an approach that is most likely to result in a satisfactory outcome to the client. Examples of such conditions include: Uterine torsion in the term mare, colic of gastro-intestinal origin in the near- term or term mare, prolapse of the rectum or urinary bladder, herniation or rupture of the abdominal body wall, hemorrhage from one or more of the large vessels in the broad ligament of the uterus, chronic laminitis, the previously diagnosed existence of a recurrent myopathy (HYPP in certain lines of the quarter horse family, polysaccharide storage myopathies in this and related breeds or equine polysaccharide storage myopathy in draft breeds), and the previously diagnosed presence of cardiovascular or respiratory disorders that would increase the anesthetic risk to the mare or simply the suspicion that the dystocia resulted during an abortion of a preterm fetus. Aftercare for mares treated for dystocia The after care of a mare that was subjected to a cesarean section falls outside the scope of this presentation, but is largely the same as for any major abdominal surgery. Apart from complications specifically related to abdominal surgery, the post-dystocia mare should be monitored and treated for the following complications:

9 Pain is a common sign in mares that suffered dystocia and should be managed as a distinct entity. Systemic treatment with non-steroidal anti-inflammatory drugs (e.g. flunixin meglumine or phenylbutazone), long-acting epidural analgesia or intra-vaginal icepacks (alone or in combination) can provide relief from various degrees of pain originating in the birth canal. Impactions are frequently encountered in post-dystocia cases. Laxatives, usually in the form of mineral oil (4-5 L, administered by nasogastric tube) are routinely administered by the author to prevent post-delivery impactions in the large bowel. While the cause is not accurately established it may relate to dehydration and reluctance to defecate due to intrapelvic pain. Apart from the administration of mineral oil most mares are also fed high volume diets with bran to soften their manure. Tetanus prophylaxis, in the form of a booster vaccination in previously vaccinated mares or by the administration of a single dose of antitoxin, is routinely included in the mare s aftercare. Vaginal or cervical trauma, while not life threatening, can seriously affect the mare s ability to conceive and carry another foal to term. Cervical lacerations are best assessed and repaired after the tissues have healed (after foal heat), but vaginal trauma needs to be attended to immediately to prevent transluminal adhesions from developing. This is easily achieved by the daily application of an oily ointment or dry-cow intra-mammary preparation onto the walls of the vagina by means of a gloved hand. Pneumo- and/or urovagina are both more frequently encountered during the postpartum period of mares that have suffered dystocias. Exercise, when possible, and the repair of any Caslick s sutures as soon as the vulvar tissues have healed and the vaginal therapy for the prevention of adhesions is completed are helpful in controlling these problems. Retention of the fetal membranes is a very common complication after dystocia and should be treated in the same manner as in spontaneously foaling mares. The administration of oxytocin in small boluses (10 IU) every 2-4 h or as a constant rate intravenous infusion (5 IU/h), continuation of broad spectrum antimicrobial therapy, administration of non-steroidal anti-inflammatory drugs and intravenous fluid administration are routinely applied to cases in the author s care. Transrectal massage of the uterus, exercise when possible and careful monitoring of the mare s temperature, heart rate and digital pulses for signs of toxemia and/or laminitis are very important as well. As soon as systemic signs of toxemia are detected, more vigorous attempts are made at removing the retained membranes and often polymixin B is added to the treatment protocol (as an anti-endotoxic agent). For further detail on the treatment of retained fetal membranes the reader is referred to other texts that deal with this subject in greater detail.

10 Metritis in the absence of retained fetal membranes is uncommon, but possible. Systemic signs include an increased heart rate and fever. Local signs include a foul smelling vaginal discharge. In the author s opinion this infection can to some extent be avoided by washing fetal debris from the uterus immediately after the delivery of the fetus and its membranes. If insufficient isotonic solution is available for this purpose (20-60 L saline), even just plain water can be used to cleanse the uterine lumen. If metritis is diagnosed in the face of adequate antimicrobial therapy, the addition of a drug specifically effective against anaerobic bacteria (metronidazole) should be considered. Ecbolic therapy with oxytocin, regular uterine lavage and preventative therapy for laminitis must be added as well. Peritonitis can occur as a result of a previously undetected uterine laceration that was possibly not even caused by any obstetric intervention (high up in the fetal horn of the uterus), but it can also result from necrosis of the uterine wall, a perforated cecum or other portion of the gastro-intestinal tract or a crushed wall of a segment of gut. Peritonitis is best diagnosed by the examination of a fluid sample obtained by abdominocentesis. While the failure to detect peritonitis at the earliest possible time after its onset seriously affects the mare s prognosis, very encouraging results have been reported after uterine lacerations and perforations were repaired surgically (17). Hemorrhage can be serious after dystocia and mares packed cell volumes and total serum protein concentrations should be monitored for at least two days after delivery. After cesarean section hemorrhage can occur into the abdomen or into the uterine lumen or both. In some cases hemorrhage may be life-threatening, even after the placement of a so-called hemostatic suture along the incised edges of the hysterotomy wound (19) and this finding has prompted one experienced surgeon to recommend that all major vessels bleeding from the hysterotomy incision be ligated individually (5). Hemorrhage can also occur from one of the major vessels in the broad ligament of the uterus. Such cases are best treated conservatively as the isolation of the bleeding vessel during a celiotomy is highly unrewarding and the mare is a serious anesthetic risk. Mastitis can develop in mares that have lost their foals during dystocia and have engorged udders. It is suggested that mares only be milked out if they develop mastitis (a hot, painful udder with signs of systemic disease). The majority of mares will not develop mastitis and not milking the mare will accelerate the involution of the mammary glands. References 1. Blanchard TL, Bierschwal CJ, Youngquist RS and Elmore RG (1983) Sequelae to percutaneous fetotomy in the mare. J. Am. Vet. Med. Assoc. 10: 1127.

11 2. Blanchard TL, Varner DD, Elmore RG, Martin MT, Scrutchfield WL and Taylor TS (1989) Management of dystocia in mares: Examination, obstetrical equipment and vaginal delivery. Comp. Cont. Educ. Pract. Vet., Equine 11: Bostedt H (1988) Zur Anwendung eines β 2 -Mimetikums (Clenbuterol) bei Graviditäts-störungen und in der Geburtshilfe des Pferdes. Tierärztl. Prax. 16: Byron CR, Embertson RM, Bernard WV, Hance SR, Bramlage LR and Hopper SA (2002) Dystocia in a referral hospital setting: approach and results. Eq. Vet. J. 35: Embertson RM (2003) Dystocia management. Proc. Ann. Conv. Am. Assoc. Eq. Pract. 49: Frazer GS (1997) Review of the use of fetotomy to resolve dystocia in the mare. Proc. Ann. Conv. Am. Assoc. Eq. Pract. 43: Frazer GS (2001) Fetotomy technique in the mare. Eq. Vet. Educ. 13: Frazer GS, Perkins NR, Blanchard TL, Orsini J and Threlfall WR (1997) Prevalence of fetal maldispositions in equine referral hospital dystocias. Eq. Vet. J. 29: Frazer GS, Perkins NR and Embertson RM (1999) Normal parturition and evaluation of the mare in dystocia. Eq. Vet. Educ. 11: Frazer GS, Perkins NR and Embertson RM (1999) Correction of equine dystocia. Eq. Vet. Educ. 11: Freeman DE, Hungerford LL, Schaeffer D, Lock TF, Sertich PL, Baker GJ, Vaala WE and Johnston JK (1999) Caesarean section and other methods for assisted delivery: comparison of effects on mare mortality and complications. Eq. Vet. J. 31: Ginther OJ and Williams D (1996) On-the-farm incidence and nature of equine dystocias. J. Eq. Vet. Sci. 16: Juzwiak JS, Slone DE, Santschi EM and Moll HD (1990) Cesarean section in 19 mares: results and postoperative fertility. Vet. Surg. 19: LeBlanc MM and Norman W (1992) Sedation and anesthesia of the mare during obstetric manipulation. Proc. Ann. Conv. Am. Assoc. Eq. Pract. 38: Leidl W, Stolla R and Schmid G (1993) Zur Schwergeburt bei der Stute I. Ursachen, konservative Geburtshilfe und Fetotomie. Tierärztl. Umschau 48: McGladdery A (2001) Dystocia and postpartum complications in the mare. In Practice 23: Sutter WW, Hopper S, Embertson RM and Frazer GF (2003) Diagnosis and surgical treatment of uterine lacerations in mares (33 cases). Proc. Ann. Conv. Am. Assoc. Eq. Pract. 49: Vandeplassche MM (1987) The pathogenesis of dystocia and fetal malformation in the horse. J. Reprod. Fert., Suppl. 35: Vandeplassche MM (1992) Selected topics in equine obstetrics. Proc. Ann. Conv. Am. Assoc. Eq. Pract. 38:

12 20. Vandeplassche MM, Simeons P, Bouters R, De Vos N and Verschooten F (1984) Aetiology and pathogenesis of congenital torticollis and head scoliosis in the equine neonate. Eq. Vet. J. 16: