A group of researchers recently evaluated how food deprivation affects a horse’s autonomic nervous system and found that it slows the animals’ heart rates, a conclusion opposite of the team’s original hypothesis.

"We were interested in assessing … whether fasting might reduce parasympathetic tone, (and in turn increase heart rate)," relayed James Jones, PhD, DVM, a professor of surgical and radiological sciences at the University of California, Davis. "We were concerned that fasting might result in an increased heart rate and also lead to gut stasis that can predispose a horse to colic."

The horse’s autonomic nervous system (ANS), which controls a number of bodily functions, includes two subsystems that control cardiac function and digestion:

• The sympathetic nervous system (SNS), which increases heart rate while inhibiting digestion; and
• The parasympathetic nervous system (PNS), which generally slows heart rate and enhances digestion.

At rest, healthy horses have a high resting parasympathetic tone, meaning their PNS dominates their SNS, resulting in a slower heart rate