Dystocia and its Management: The Equine
Anju Kujur1, Sunita Kumari Murmu2, Nirmala Minj3
1 Phd Scholar, Division of Animal Reproduction, ICAR-Indian Veterinary Research Institute, Bareilly-243122
2 Touring Veterinary officer, Haldipokar, East Singhbhum
3 Assistant Professor cum junior Scientist, LPM, BAU, Jharkhand
Abstract
Dystocia in mares is a rare occurrence, but when it does occur, it is a genuine emergency. The most prevalent cause of dystocia is malposture of a long foetal extremity or head deviation due to the lengthy extremities and powerful contractions that occur during parturition. Despite the fact that numerous other prenatal causes of dystocia have been identified, they appear to be far less common. In the mare, uterine torsion, uterine inertia, and disorders that cause restriction of the birth canal are uncommon. Assisted vaginal delivery, controlled vaginal delivery, fetotomy, and caesarean section are some of the methods for dealing with dystocia in mares that have recently been documented, however dystocia management for difficult cases in mares requires specialised hospital facilities and a team of professionals.
Keywords: Parturition, maldisposition, dystocia, management
Introduction
One of the most challenging circumstances for veterinarians to deal with is dystocia in mares. Dystocia is a term that describes a problematic or difficult birth. Approximately 4% of Thoroughbred foalings experience dystocia or difficult birth. Dystocia seems to be more likely in mares giving birth for the first time (i.e., maiden mares) than those who have given birth to one or more foals previously. It is necessary to comprehend or manage dystocia by first understanding the usual occurrences of parturition in mares. The standard gestation time for a mare is 340 days, however due to the fetus’s developmental delays, parturition can take up to 385 days. However, foaling might take up to 315 days in some mares. Because the indications of parturition in mares are less prominent than in cattle, it can be difficult to determine the proper time for parturition. The symptoms of impending parturition include the relaxation of sacrosciatic ligaments, which are less prominent due to thick croup muscles, and the waxing of teats, which can be noticed before 24-48 hours of foaling but only in a few mares. Parturition in mares is a quick and voilent process where in the foetus is delivered within 30-70 minutes following the chorioallantoic membrane ruptures. Sweating and frequent urination characterise the first stage of Parturition, which lasts 15-90 minutes. It is important to recall that the chorion’s outer surface is deep red in colour and velvety in appearance upon delivery. In contrast to cattle, the amnion is opaque blueish white, with the foetal parts not readily apparent. The start of the second stage of labour comes on quickly. It is distinguished by the appearance of the water bag or the start of the process of compelled straining. The mare falls to the ground quickly, and a foetal leg appears. One of the foetal legs is missing until foetal delivery, around 6 inches ahead of the second leg. Looking at the powerful, painful contractions that occur during foal delivery, the quickness of foetal delivery, the pressure to save the mare and foal’s lives due to high costs, early placental separation, and the complications that can occur in a badly attended or unattended difficult mare delivery.
Dystocia in horses manifests as:
The first stage of labour takes a long time. Even 20-30 minutes after the rupture of the chorio-allantoic membranes and the flow of fluids, there was no development in the second stage of labour. Increased straining severity even one hour after the water bag ruptured, there were no foetal remains in the vaginal area. There has been no progress in straining and unable to lie down. The chorio-allantoic membranes separate prematurely (Red bag condition). The first stage of labour was pleasant, but the second stage failed to begin (Uterine inertia), Constant squeezing with no cervical discharges or foetal fluid discharge (Incomplete cervical dilation, uterine torsion).
Incidence of dystocia
The incidence of dystocia in mares is substantially lower than in cattle. Dystocia affected 10.1 percent of all pregnancies, with thoroughbred mares having a greater risk of recurrence than Quarter Horse mares.
Table1: Factors that contribute to the occurrence of dystocia:
| Factors | Incidence |
| Age | Common in old mares |
| Sex of the fetus | More with male fetus |
| Parity | More in Primiparous |
| Breed | Through breeds (4%), Belgian draught mare and Shetland ponies (10%) |
| Species | Less occurrence in Miniature pony mares, feral equids |
Causes of dystocia:
The most common cause of dystocia in mares is malposition of the long foetal extremities, while positional and presentational anomalies can occur, albeit to a lesser extent. The mare exhibits many, but not all, of the reasons of dystocia in cattle. Even though the etiology of dystocia in horses can be divided according to maternal and foetal origins, most records show that foetal maldisposition (flexion of limbs and head deviation) and obstruction of the birth canal (uterine torsion) are the most frequent cause of dystocia in mares.
Fetal causes
- Fetal maldisposition
- Presentation abnormality
- Abnormal position
- Abnormal Postures
- Fetal oversize
Maternal Causes
- Uterine inertia
- Failure of abdominal expulsive forces
- Incomplete cervical dilation
- Uterine torsion
- Uterine rupture
- Deviation of uterus
Table2: Incidence of equine fetal maldispositions:
| Maldispostion | Incidence |
| Bilateral carpel flexion with other deformity most common | 10% |
| Transverse Presentation | 18% (Draft breeds)
8% (Light breeds)
|
| Malposture
Anterior Presentation
Post Presentation |
86%
68% Limb Flexion 52% Head Flexion 37% Lateral Position 11% 16% Hip Flexion 50% Hock Flexion 25% Others 25% |
| Neck Deviation | 35% |
| Fetal oversize | 1.3% |
Management of Dystocia
When there is a dubious instance of dystocia in a mare, the obstetrician should be contacted as soon as possible. Because the second stage of labour is usually quite brief and lasting about 20 to 30 minutes, mare owners should be advised to keep their mares walking to avoid pain and staining. The pregnant mare’s history should be clarified, including behaviour, posture, nature of breathing, degree and frequency of straining and condition of allantochorion, foetus and vulva. It is necessary to conduct a thorough and quick inspection. Before rectal and vaginal examinations, the perineum should be cleansed. To assess the foetal and cervical status, a rectal examination should be performed first. An epidural anaesthetic can be administered to allow for a more thorough examination. The foaling mare should be approached with caution since it can exhibit erratic behaviour. Lubricants such as petrolium jelly, J-Lube, or methylcellulose can also be used to lubricate the birth canal and can be pushed into the uterus with the stomach tube. Obstetric manipulations should be conducted quickly, manipulation of a live foetus should last no longer than 30 minutes and if the foetus is dead, manipulations should last no longer than an hour. Even if the foetus is deceased, persistent dystocia can cause considerable cervical injury and/or ischemia in the caudal reproductive canal, which can result in scarring, adhesion development and possibly systemic illness.
Sedation/Anesthesia
Sedation/tranquillization of mares may be required for examination and/or manipulation. In anxious mares, sedation is required.
Table3: Suggested sedative and induction drugs for the pregnant mare
| Drug | Dose & Route | Duration |
| Xylazine |
0.2–1.0 mg/kg IV,
|
20–30 min |
| Detomidine | 0.002–0.040 mg/kg IV, IM, sublingual | 30–60 min |
| Detomidine infusion Initial bolus: | Initial bolus:0.0075 mg/kg
Start infusion at: 0.0006 mg/kg/min IV, infusion rate is halved every 10–15 min |
Sedation lasts approx. 15–30 min after the infusion is stopped |
| Dexmedetomidine | 0.0025–0.005 mg/kg IV, IM | 20–40 min |
| Acepromazine | 0.01–0.04 mg/kg IV, IM, sublingual | 60–240 min |
| Ketamine | 2.2–2.5 mg/kg IV | 15–20 min |
| Diazepam | 0.08–0.1 mg/kg IV or combined with ketamine IV | 15–20 min |
| Guaifenesin | 50–100 mg/kg IV infusion | 20–30 min dose dependent duration |
| Guaifenesin, ketamine, xylazine | Guaifenesin: 50 g Ketamine: 1–2 g Xylazine: 500 mg IV infusion in 1L dextrose or saline | Give to effect, sedation/relaxation duration are dose dependent |
Methods of Dystocia handling:
Traditionally, dystocia repair procedures were separated into three categories: mutation-forced extraction, fetotomy, and caesarean section. Assisted vaginal delivery, controlled vaginal delivery, fetotomy and caesarean section are some of the more contemporary approaches. There is no process that is superior to another. The viability of the pregnancy, past handling, case economics, obstetrician clinical abilities, and proximity to a well-equipped hospital are all key factors that a veterinarian must evaluate before deciding on the best course of action.
Assisted vaginal Delivery
The mare is alert and supported to a little or big degree for vaginal delivery of an intact foal within 10-15 minutes with assisted vaginal delivery. If the dystocia does not resolve in 10-15 minutes, the obstetrician should investigate further options for dystocia correction. With the mare standing and sedated, this procedure can be conducted on the farm or in the clinic. To assist the mare in delivering the foal, the veterinarian may employ instruments like as chains or a head snare. “To avoid rib fractures, the mare should be permitted to continue delivery herself once the (foal’s) rib cage enters the pelvic canal.
Controlled Vaginal Delivery
Controlled vaginal birth aided by general anaesthesia and the raising of the mare’s hindquarters. The uterine relaxation and gravity’s impact are employed to aid foetal repulsion and manipulation in this treatment. Early after delivery, the position and posture of the foetus is identified, followed by repulsion. The benefits of this approach are obvious: the foal can be manuplulated without the mare’s pressure and the foal can be repulsed, allowing for additional manipulation space.
Fetotomy
If the foetus is proven to be dead and the fetotomy is conducted by trained personnel, many of the maldisposed foetuses can be safely resolved for vaginal birth by fetotomy; otherwise, fetotomy is potentially harmful for the mare (Higgins and Wright, 1999). One or two well-placed fetotomy cuts can significantly reduce intervention time and allow for a painless delivery of a nonviable foetus. The worth of mare is a crucial aspect to consider. One study found that one or two cuts were enough to repair 57% of instances, while another 21% required a third cut. Due to the longer and softer horse birth canal and the dangers posed by rapidly separating foetal membranes, the fetotomy process is more difficult than in the cow. The absence of foetal reflexes (no limb withdrawal, no ocular reflex, no swallowing response, no heart beat, and no anal reflex) indicates foetal death. The survival percentage of mares following fetotomy was 95.8%. Retained foetal membranes (5.5 %), laminitis (6.9%), vaginal and cervical lacerations (2.8 %), and delayed uterine involution (2.8%) are all consequences of fetotomy. Mare fertility looks to be strong in the short and long term, with 80 to 83 %of mares conceiving.
Cesearean section
When an appropriate surgical facility is absent, a Caesarean section in the mare is still considered a difficult and complicated intervention. Mare survival is high (89% to 95%) when a proper hospital facility and current techniques for inducing and sustaining general anaesthesia are used. If the procedure is undertaken after the mare has been subjected to extended vaginal manipulations, the prognosis for future fertility is likely to be poor. When the procedure is performed early, the foal survival rate is high (38% in emergency caesarean versus 90% in elective caesarean). The prognosis for foal survival after a caesarean section is dismal. If the foal is alive within the maternal pelvic canal, it will die of anoxia due to the dehiscence of the allantochorion within 1 or 2 hours of the start of the second stage of labour; therefore, if the foal is alive the operation should be done as soon as possible. Due to a dearth of equine specialised facilities and a drop in the number of equines kept internationally, caesarean section in the equine species is limited to only a few locations.
https://www.pashudhanpraharee.com/overview-of-infertility-in-the-bitch/
Conclusion:
Reproductive trauma, placental retention, delayed uterine involution, uterine infection, uterine artery rupture, uterine prolapse, vulva, vaginal, or uterine lacerations, constipation, and colic are among the complications associated with dystocia. So proper care and management during the parturition in mare is important factor to maintain the health of both foal and mare.
