Direct measurement of biliary bilirubin excretion in ponies during fasting.

The research study focuses on the examination of bilirubin excretion during feeding and fasting periods in three female horses with external biliary fistulas. It was found that the bilirubin excretion rate did not change significantly between feeding and fasting periods, and that the increased bilirubin levels during fasting were attributed to a decrease in plasma bilirubin removal and not an increase in bilirubin supply into the plasma.

Understanding the Study

• The study involved three pony mares or female horses that had chronic external biliary (T-tube) fistulas, a kind of abnormal connection originating from the bile duct.
• The researchers examined the biliary excretion of bilirubin, a bile pigment produced as a byproduct of red blood cells breakdown in the liver, during two different states: during feeding and during a fasting period of 2.5 days.
• Bilirubin excretion, including its conjugate composition or paired compounds, was directly measured rather than determined through indirect tests or calculations.

Key Findings of the Study

• The rate of bilirubin excretion during fasting (1.96 +/- 0.74 microgram/min/kg of body weight), once a new steady state was established, did not show substantial differences from the excretion rate during feeding (1.99 +/- 0.45 microgram/min/kg). This implies that the horse’s feeding or fasting state does not significantly impact the rate at which bilirubin is excreted from the body through the biliary system.
• The researchers observed hyperbilirubinemia, a condition characterized by excess levels of bilirubin in the blood, during fasting. However, this condition stemmed from a reduced removal of plasma bilirubin, as opposed to an increased input of bilirubin into the plasma. This means that the excess bilirubin was not due to overproduction of the bile pigment but rather due to the reduced ability of the body to remove bilirubin from the plasma.
• The relative plasma excretion of the individual conjugate fractions of biliary bilirubin was not affected by fasting. This means the fasting state does not impact the proportional discharge of various compounds paired with bilirubin in the form of biliary excretion.