David Freeman, MVB, PhD, Dipl. ACVS, Appleton Endowed Professor at the University of Florida College of Veterinary Medicine, in Gainesville, sought to provide clarity during his presentation at the 2021 British Equine Veterinary Association Congress, held Sept. 4-7 virtually and in Birmingham.
Peripartum (before giving birth) abdominal pain has three possible causes, he said:
- Normal parturition, where foaling is completed at the expected rate, and after delivery, the mare is more comfortable.
- Dystocia (difficult birth) with prolonged or variable stages one and two of parturition (foaling).
- Colic, which can have various effects on the delivery process and requires specific diagnostic tests to determine the cause.
Knowing What’s Normal
Because foaling is an inherently painful process, owners and veterinarians must understand the steps and signs of normal parturition before they can determine if the mare’s experiencing colic.
Freeman explained that the first stage of pregnancy typically includes active uterine contractions and dilation of the cervix. It should last 30 minutes to four hours, with the mare displaying very few signs of discomfort.
The second stage is far more dramatic, he said, characterized by the foal’s entrance into the birth canal, rupture of the allantoic sac, abdominal contractions, and delivery of the foal. This stage normally lasts five to 40 minutes.
Just before parturition starts, a normal foal lies so its dorsal aspect (back) is toward the ventrum of the mare. The front and hind feet and neck are flexed. During delivery, the foal’s hind limbs extend in dramatic form when the stifle encounters the brim of the pelvis and the reciprocal apparatus forces all the joints to go into rapid extension, Freeman explained.
“If the feet engage the uterine horn at this point, they can lacerate the uterus and create a uterine tear,” he said. “They can also hook a viscus in the abdomen and tear its attachments, which can cause catastrophic injury.”
Causes of Colic in Broodmares
“Any colic of gastrointestinal origin can develop at or during parturition, either as a coincidence or as a consequence of parturition,” said Freeman. “Some colics of gastrointestinal or urogenital origin are specific to parturition—they can precede or coincide with parturition, or they can be related to parturition. The important signs are those that persist after parturition. This is critical for your diagnostic steps.”
He said the types of intestinal disease that can occur in the peripartum period (shortly before, during, and immediately after giving birth) are essentially the same as you’d encounter in any horse at any time, including colitis, small intestine obstruction or strangulation, impaction, gas distention, and more. Serious conditions to be particularly aware of in late-term mares include:
- Large colon volvulus Freeman said this well-recognized cause of colic is responsible for 17-21% of all colic surgeries. Veterinarians see it most commonly in postpartum broodmares, but it can also develop during parturition.
- Tears The extension of the foal’s hind limb as it moves into position for delivery can cause structures and tissues such as the uterus, broad ligament, and jejunal mesentery to tear.
- Avulsion of the small colon from the mesocolon Freeman explained that this occurs when the foal’s foot engages the edge of the small colon and tears it off the mesenteric attachments.
- Cecal rupture or tear This can be mistaken for dystocia. Affected mares go into rapid endotoxemic shock and require assisted delivery. They must be euthanized, he said.
- Diaphragmatic hernia A previous or current parturition can cause a hernia. While small ones might be reparable, Freeman said large defects can require euthanasia of the mare.
- Urinary tract injuries If a urogenital tract laceration is large enough, other abdominal organs (e.g., intestines, bladder) can prolapse through it. These mares can develop tears in the urethra and bladder itself, said Freeman.
- Uterine torsion This condition causes low-grade colic similar to impaction colic. While it most commonly occurs in late gestation, on rare occasions it can develop shortly before parturition.
Should You Do a Cesarian Section?
This question arises frequently when managing mares with gastrointestinal or reproductive tract causes of colic that have not yet delivered the foal, said Freeman. However, “rarely, if ever, is a C section needed during colic surgery,” he said. “It’s usually done for the wrong reasons, such as to improve access or recovery. There are so many other ways to ensure a good outcome that it’s not necessary to do a C section.”
He warns a C section is likely to increase mare and foal mortality, partly because you might deliver a premature foal. Further, Freeman said, it adds a surgery and its associated risks, often to a horse that’s already undergoing major colic surgery.