Measurement of haptoglobin in saliva of cows: Validation of an assay and a pilot study of its potential application.

In recent years, the use of saliva as a matrix for the measurement of biomarkers of health and welfare is gaining importance due to its non-invasive collection. Haptoglobin (Hp) is an acute-phase protein involved in the inflammatory response and changes in its concentration can provide information about the health status of the animals. This study aimed to develop and validate an assay based on luminescent amplification (AlphaLISA technology) for the measurement of Hp in bovine saliva and to study the possible changes in different inflammatory situations such as peripartum period and lameness. The assay proved to be accurate, reliable, and sensitive for the measurement of Hp in cow saliva (coefficient of variation (CV) 7.57%; coefficient of determination (R2) 0.992; recovery test 105.15%; lower limit of quantification (LLQ) 7.9 ng/ml). Significant differences were observed between Hp levels in saliva of cows before (13 days before) and after (7 and 20 days after) calving and at the moment of calving (p < 0.0001), and between lame and healthy cows (p < 0.008). In conclusion, this assay can detect Hp in a precise, sensitive, and accurate way in saliva of cows. Future studies with a larger population and different disease conditions should be conducted to determine the potential of Hp as an inflammatory biomarker in cow saliva.