Objective: To test the hypothesis that oxytocin could alter gastrointestinal motility and, therefore, be potentially useful as a prokinetic drug in the horse.

Method: On day 1, 200 barium-impregnated polyethylene spheres (diameter=3.2, weight=20mgr) were administered to each of 30 healthy, adult Warmblood horses via nasogastric intubation. During the next three days the following variables were recorded: gut motility, defecation frequency per day, weight of feces per defecation and intestinal transit time. On day 5, following the administration of barium spheres, horses were randomly separated in two even subgroups. The first subgroup received 0.07IU/kg of oxytocin intravenously while the second subgroup received 0.14IU/kg. During the next three days the same variables were recorded of each horse.

Results: Oxytocin administration led to a statistically significant increase in gut motility (p<0.01 for subgroup 1 and 2). That increase was transit, lasting for almost an hour post-administration and was more consistent for subgroup 2. As far as defecation frequency and fecal weight are concerned, it seems that oxytocin administration led to small but statistically significant increase in both subgroups which was noted only for the day of oxytocin’s administration. Oxytocin administration led to a faster intestinal transit time in both subgroups (p<0.001). It is worth noting that although no statistically significant difference was found between the two subgroups in any of the variables, 3 horses of the second subgroup showed signs of abdominal discomfort that reached its peak 35 minutes post-administration and subsided spontaneously within 30 minutes.

Conclusion: Oxytocin could be useful as a prokinetic drug in cases of gastrointestinal disease as it increases gut motility, daily defecation frequency, fecal weight per defecation and intestinal transit time. Moreover, this effect was not found to be non-dose dependent, therefore the lower dose is recommended.