All types of horses can get colic, but in the pregnant mare, the painful signs of colic might be caused by something other than a gastrointestinal problem. The mass of the foal and placenta causes a lot of crowding in the mare’s body, and uterine torsion–a twisted uterus–can be the result. But there is good news; a recent study found that at less than 320 days of gestation, chances are quite good that both mare and foal will survive uterine torsion with proper treatment. And there is a good chance the mare will be sound for future breeding after recovery.

Kristin Chaney, DVM, a resident at Michigan State University, described the study at the 52nd annual American Association of Equine Practitioners convention, held Dec. 2-6, 2006, in San Antonio, Texas. The retrospective study evaluated records of 63 mares with uterine torsion treated at four referral hospitals from 1985-2005, and it found a survival rate for mares of 84% (53 of 63 mares). “Two factors significantly affected survival: stage of gestation and heart rate at admission,” reported Chaney.

At more than 320 days of gestation, only 17 of 26 mares (65%) survived; she explained that at this stage, increased fetal size and weight complicate correction techniques. At less than 320 days of gestation, 97% of mares survived (one mare of 37 studied was euthanatized after a catastrophic accident during recovery). The study also found mares that survived had considerably lower heart rates than those mares that did not survive (59 beats per minute compared to 74 beats per minute). Although the data were not statistically examined, subjectively it didn’t appear that heart rate correlated with the degree of torsion or degree of pain, commented Chaney.

Overall foal survival rate was 54%. In those uterine torsion cases that occurred before 320 days of gestation, 72% of the foals survived (21 of 29) compared to 32% of foals (eight of 25) in pregnancies past 320 days. Ten mares aborted prior to discharge from the hospital and five full-term mares delivered live foals via Cesarean section at the time of correction (four of the foals survived). Of the 30 mares that went home pregnant and were available for follow-up, 25 had healthy foals