• horse;
  • lactose 13C-ureide breath test;
  • 13C-octanoic acid breath test;
  • orocaecal transit time;
  • dual stable isotope breath test;
  • small intestinal transit


Reasons for performing study: Application of the lactose 13C-ureide breath test (LUBT) for measurement of equine orocaecal transit time (OCTT) has not been reported previously. The ability to assess OCTT noninvasively, and to investigate its relationship to gastric emptying rate and small intestinal transit, would be of both clinical and research value.

Objectives: 1) Assessment of the LUBT in healthy horses, with comparison of induced versus noninduced test protocols. 2) Application of a new dual stable isotope breath test (lactose 13C-ureide and 13C-octanoic acid) for gastrointestinal transit measurement.

Hypothesis: The LUBT will allow quantification of equine OCTT, and test efficacy will be enhanced by prior administration of lactose 12C-ureide as shown in vitro. The dual tracer breath test will permit simultaneous measurement of gastric emptying, OCTT and small bowel transit times.

Methods: Induced and noninduced LUBTs were performed in 3 healthy mature horses in randomised order using a standard test meal and protocol. Combined LUBT and 13C-octanoic acid breath tests (13C-OABT) were performed in 4 individuals on 4 occasions at weekly intervals. Expiratory isotopic recovery was modelled to allow generation of gastric emptying data, small bowel transit times and caecal transit parameters.

Results: The induction protocol for the LUBT increased the rate and magnitude of expiratory 13CO2 significantly. Mean ± s.d. values for OCTT, caecal lag phase (tlag) and caecal t1/2 using the induced LUBT were 3.24 ± 0.65 h, 5.62 ± 1.22 h and 6.31 ± 1.21 h, respectively. Dual stable isotope tests resulted in the production of 2 discrete peaks in expiratory 13CO2 in 15/16 tests from which gastric t1/2, OCTT and small bowel transit (SBT) parameters could be calculated.

Conclusions: The induced LUBT provides a reliable noninvasive measure of equine OCTT and can be paired with the 13C-OABT to provide further information about small intestinal motility.