Gas handling in the caecum of the horse.

This study investigates how gas is processed in the largest part of a horse’s large intestine, the caecum, by measuring pressures inside the caecum of ponies through an observational technique called endoscopy. Researchers observed changes in this process during different times of the day and after feeding, and took further measures to understand the movement and pressure regulation of gas within the digestive system.

Methodology and Observations

• The researchers used a combination of two techniques – electromanometry for recording pressures and endoscopy for direct observation of the caecum.
• These chronically cannulated ponies’ caecal pressures were recorded while observing the caecal base and the dome-shaped top region of the caecum called the cupola.
• The seals used to make these measurements were gas-tight to ensure accuracy in measurement of gas pressures.
• They noticed that the baseline pressure for gas in the upper layer of the caecum, known as the gas cap, was generally below atmospheric pressure, indicating that gas pressure inside the intestines tends to be lower than outwards pressure.
• This pressure became less negative after the ponies consumed food. This indicates how the process of digestion can affect gas management inside the caecum.

Diurnal Variations and Post-meal Enhancements

• Transitions during a day were noticed in terms of the intensity and frequency of these pressure readings.
• The pony’s caecum’s movement and pressure shifts were observed, and they occasionally revealed momentary positive pressures inside the gas cap.
• The heightened activity in the caecum after eating, known as a paraprandial phase, was associated with enhanced functioning of the caecum.

Manipulation and Regulation

• The investigators also manipulated the volume of the caecal gas cap with an inert gas, nitrogen. This analysis provided insights into how the caecum could control gas pressures and remove gases produced during fermentation.
• The bottom part of the caecum demonstrated the ability to regulate and balance these gas pressures effectively.