Blood ATP luminometry and dynamic viscoelastic coagulometry reference values in healthy newborn dairy calves

<h2>Abstract</h2> The primary objective of this study was to determine reference blood values for adenosine triphosphate (ATP) luminometry and dynamic viscoelastic coagulometry analysis in healthy newborn dairy calves, to evaluate their potential usefulness for future on-farm detection of sepsis. Secondary methodological objectives were to assess wether ATP luminometry results were influenced by blood collection method, blood matrix (serum, plasma or whole blood), or the addition of a stabilizing solution aimed at minimizing baseline relative light unit (RLU) values. Twenty-one and 19 healthy calves were included in the study for ATP luminometry and dynamic viscoelastic coagulometry analysis, respectively. ATP measurements were performed using AquaSnap Total and AquaSnap Free swabs across the different blood matrices, with and without stabilizing solution. Hemoglobin concentration and hematocrit were measured to account for potential effects of hemolysis and dilution on ATP results. No significant differences in RLU values were observed between sampling methods. Baseline ATP luminometry values were high across all matrices, with median RLU values of 5,062 for serum, 7,198 for plasma, and 7,547 for whole blood, and substantial interindividual variability, particularly for serum and plasma samples. The addition of stabilizing solution did not reduce baseline RLU values, and neither hemoglobin concentration nor hematocrit allowed for meaningful normalization between individuals. In contrast, dynamic viscoelastic coagulometry demonstrated narrow reference ranges and low interindividual variability, with median (interquartile range) values of 172 (154–192) seconds for activated clotting time, 25 (18–34) units/minute for clot rate, and 3.30 (2.70–3.90) units for platelet function. Overall, these findings indicated that ATP luminometry, under the conditions evaluated, show practical and methodological constraints. Conversely, dynamic viscoelastic coagulometry analysis shows promising analytical stability and warrants further investigation in clinically septic calves to determine its potential for early on-farm sepsis detection in newborn dairy calves.