Large intestinal capacity, retention times, and turnover rates of particulate ingesta associated with extensive large-colon resection in horses.

The research article investigates the effect of extensive colon resection surgery on horses’ digestive process, particularly how waste products are moved and eliminated. The study utilized specific indicators and mathematical calculations to understand small and large intestine capacity, retention times, and turnover rates.

Overview of the Procedure

• The experiment involved nine horses that were divided into two groups. Group 1, consisting of three horses, was sham-operated (placebo surgery group), while the remaining six horses underwent extensive large colon resection (colon removal).
• Excretion of a particulate marker called Ytterbium (Yb) was monitored on these horses before, and at varying durations (3 weeks, 3 months, 6 months) post-surgery. The amount of Yb in their feces served as a trackable marker of digestive function.
• A total of five Yb excretion parameters were recorded and analyzed: total Yb excretion, logarithm-base-e of Yb excretion, percentage of Yb excretion, logarithm-base-e of percentage Yb excretion, and cumulative percentage of Yb excretion.
• Observations were statistically analyzed for differences between the resected and sham-operated horses, as well as within each group.

Findings and Interpretation

• The study revealed that horses that underwent colon resection had significantly quicker transit, peak, and mean retention times when compared with both preoperative measures and the sham-surgery group.
• Two ‘mixing pools’ were identified in the digestive process. These pools indicate two stages of digestion, each with unique retention times. The first pool empties relatively slower (at 5.7% per hour), while the second one was faster (at 12.3% per hour).
• The colon resection did not impact the rate of passage from the first pool. This suggests that this phase of the digestion process is mainly influenced by the cecum, another part of the horse’s digestive tract, with a capacity approximating that of the first pool (approximately 17 liters).
• The capacity of the first pool expanded significantly in the resected horses within 6 months of the operation, indicating an adaptation to the change in colon length.
• The rate of waste passage from the second pool accelerated immediately after the surgery but returned to its original rate 6 months after the operation.

Based on these findings, the study helps to better understand how horses’ digestive physiology adapts following a large colon resection, which is beneficial for post-surgical care and recovery strategies.