Surface electromyography as a non-invasive method for detecting stress-induced changes in gastrointestinal motility in pigs

Surface electromyography of the gastrointestinal tract is a non-invasive method for monitoring smooth muscle myoelectrical activity and provides an integrated assessment of gastrointestinal motility. Although prolonged or marked stress is known to impair digestive efficiency in livestock, partly via cortisol-mediated modulation of gastrointestinal smooth muscle activity, it remains unclear whether a single mild stressor can induce detectable alterations in motility. Therefore, this study aimed to determine whether a single mild, experimentally induced stressor alters gastrointestinal motility in pigs and whether surface electromyographic measurements are sufficiently sensitive to detect these changes. Four growing pigs were examined using a within-individual experimental design on a baseline control day and on a treatment day involving intravenous administration of adrenocorticotropic hormone (10 micrograms per kilogram body weight) to induce a mild stress response. Gastrointestinal smooth muscle electrical activity was recorded non-invasively using surface electromyography, and repeated blood samples were collected to determine serum cortisol concentrations over time. Adrenocorticotropic hormone administration produced a clear, time-dependent increase in serum cortisol concentrations, confirming the effectiveness of the experimental stress model. This endocrine response was accompanied by a significant reduction in small intestinal smooth muscle activity, whereas gastric and large intestinal activity showed no statistically significant changes, although a consistent tendency toward reduced motility was observed under stress. These findings indicate that small intestinal myoelectrical activity is particularly sensitive to mild endocrine stress and demonstrate that non-invasive surface electromyography can detect stress-related alterations in gastrointestinal function. This approach may provide a useful tool for investigating stress physiology and monitoring digestive function in livestock.