Effects of total parenteral nutrition and electrolyte solutions with or without glutamine on the hormonal profiles of horses subjected to exploratory laparotomy

Starvation and nutritional support clinically influence horses, particularly during the treatment of gastrointestinal diseases and post-surgical recovery. In this study, we aimed to evaluate the effects of different nutritional strategies on the endocrine response of horses subjected to exploratory laparotomy followed by food deprivation. Sixteen healthy adult horses were randomly allocated into four groups (n=4) based on treatments: enteral fluid therapy without (ENTFL) or with glutamine (ENTGL), and parenteral fluid therapy with glucose (PARFL) or total parenteral nutrition with glutamine (PARGL). Treatments were administered for 144 hours of starvation followed by 144 hours of refeeding. Blood samples were collected at five time points for hormonal (leptin, ghrelin, adiponectin, cortisol, insulin, free T3, and free T4) analyses. Serum insulin and glucose significantly varied across all groups, with the PARGL group exhibiting hyperinsulinemia and persistent hyperglycemia during starvation. No significant alterations in free T3 or T4 concentrations were observed, which is potentially attributed to elevated serum glucose levels maintaining thyroid hormone stability. Notably, cortisol levels increased in the ENTGL group 72 hours after the onset of starvation. Ghrelin significantly increased only in the PARGL group during starvation, and it decreased after refeeding. Adiponectin levels were enhanced in the PARFL group during deprivation, which dropped after refeeding. Starvation reduced leptin levels in the ENTGL and PARGL groups, which were increased after refeeding. Despite hormonal changes, enteral nutrition maintained glycemic control, indicating stable intestinal absorptive function. These findings highlight the influence of nutritional route and composition, especially glutamine and glucose, on endocrine adaptation during starvation and refeeding. However, limitations such as the small sample size and absence of an absolute fasting group constrain the interpretations. Future studies involving broader hormonal panels and longer follow-up can better clarify neuroendocrine regulation during nutritional stress in horses.