Draft horses weighing more than 1,500 pounds are at greater risk of postoperative complications due to anesthesia than lighter draft horses, according to a Purdue University study.

“Heavy draft horses had significantly more postoperative complications than lighter draft horses (in the study),” researchers said. “The duration of anesthesia in heavy draft horses was significantly longer than light draft horses. We suspect that the overall physical size of the heavy draft horses contributed to long anesthetic and preparation times.”

Researchers compared records of 72 draft horses that underwent surgery for acute abdominal pain between October 1983 and December 2002. They found that the heavier draft horses required longer durations of anesthesia, exhibited more postoperative complications, and had a greater mortality rate than their lighter counterparts.

The study showed that 76% of heavy draft horses recovered from anesthesia had postoperative complications, and 48% of those were discharged from the clinic. This is in comparison to a 58% postoperative complication and a 70% survival rate in non-draft horses undergoing the same types of procedures. The overall short-term survival rate of heavy draft horses in the study was 60%