Bit chewing aids gut motion in horses, study findings suggest

Bit chewing is potentially a safe, inexpensive and effective clinical treatment to improve small intestinal motility in horses, according to researchers.

Ileus, or a temporary lack of intestinal motility, is a common life-threatening problem in horses, especially after abdominal surgery.

While multiple drug treatments have been investigated with varying degrees of success, each has potential side effects, variable efficacy, and an increased cost for owners.

Molly Patton and her fellow researchers, writing in the journal Animals, noted that, for human patients suffering from ileus, sham feeding in the form of gum chewing has shown promising results in improving clinical signs and increasing gastrointestinal motility.

“Bit chewing, a form of sham feeding for horses, has also been proven to decrease gastrointestinal total transit time,” the study team said.

“However, ileus in horses typically affects the small intestine, a part of the gastrointestinal tract that has not been investigated in regard to bit chewing.”

The researchers in the Virginia Tech study set out to determine whether bit chewing shortens the gastric emptying time, small intestinal transit time, and total orocecal transit time in clinically normal horses. Orocecal transit time refers to the overall transit time from the stomach to the cecum.

Nine horses, comprising six Quarter horses, one Appaloosa, one Tennessee Walking Horse and one Warmblood, were employed in the study, which used a crossover design.

The horses, who were brought in from pasture to be stabled for the experiment, were randomly assigned to a bit-chewing group or control (no bit) group via a coin toss for the first trial period.

After the first trial period, all horses were returned to the same pasture for a washout period. The second trial period was conducted the same way, with the horses assigned to the other group (bit chewing or control).

To standardize the feeding schedule and simulate conditions similar to those of a horse undergoing treatment for colic, the horses were fasted for 12 hours before the start of the study. They followed a refeeding schedule typical for a horse recovering from abdominal exploratory surgery.

Gastrointestinal motility in the horses was compared between the groups based on acetaminophen serum levels as a marker for gastric emptying times.

Three video endoscopy capsules, which capture video images for later retrieval when they are passed in the feces, were also given to each horse without sedation via a nasogastric tube after the initial 12-hour fast in order to determine gut action.

Each horse in the bit-chewing group had an apple-flavored snaffle bit placed in their mouth for twenty minutes every six hours until all capsules were retrieved or until the end of the study period.

The captured video footage retrieved from the capsules was time-stamped, enabling the researchers to assess and calculate the timing of the capsules’ passage through the gut.

Bit chewing was tolerated well by all horses in the study without any complications or side effects, the study team reported.

The results indicated a significantly shortened total orocecal transit time after bit chewing, indicating a more active gut.

“Bit chewing,” they said, “is potentially a safe, inexpensive, and effective clinical treatment to improve small intestinal motility in horses.”

The authors said that while not all data comparisons in the present study were statistically significant (gastric emptying and small intestinal transit times), the total orocecal transit time was significantly shorter in horses during bit chewing than in the controls.

The researchers stressed that while their findings provide further promising evidence that bit chewing may have a positive prokinetic effect on total orocecal transit time in clinically normal horses, it does not prove that bit chewing will increase gastrointestinal motility in all normal horses or clinical horses suffering from ileus.

Additional larger studies evaluating the specific effects of bit chewing on total orocecal transit times are warranted, ideally using multiple gastrointestinal motility measurement methods in horses with clinical disease.

The study team comprised Patton, Sophie Bogers, Harold McKenzie III, Stephen Werre and Christopher Byron, all with Virginia Tech; Frank Andrews, with Louisiana State University; and David Wong, with Iowa State University.

Patton, M.E.; Andrews, F.M.; Bogers, S.H.; Wong, D.; McKenzie, H.C., III; Werre, S.R.; Byron, C.R. Effects of Bit Chewing on Gastric Emptying, Small Intestinal Transit, and Orocecal Transit Times in Clinically Normal Horses. Animals 2023, 13, 2518. https://doi.org/10.3390/ani13152518

The study, published under a Creative Commons License, can be read here.