Validation of the Measurement of Beta-Hydroxybutyrate and Non-Esterified Fatty Acids in Bovine Saliva: A Pilot Report

Serum beta-hydroxybutyrate (BHB) and non-esterified fatty acids (NEFAs) are biomarkers of situations of negative energetic balance in bovine. However, knowledge about their possible measurement and use in saliva is limited. In this report, two commercially available methods for the measurement of BHB and NEFAs were validated for use in bovine saliva. Both methods showed good precision and accuracy. The BHB concentrations were correlated between the saliva and the serum, but not the NEFA concentrations. The cows with hyperketonemia (<i>n</i> = 17) had increased salivary BHB compared to the cows with no clinical signs and no hyperketonemia (<i>n</i> = 34) and those with clinical signs of metritis (<i>n</i> = 17). The salivary NEFA concentration increased in newborn calves (<i>n</i> = 10) on days 1 and 2 of life compared to the day of birth before colostrum intake. The calves with symptomatic bovine respiratory disease complex (BRD, <i>n</i> = 7) showed higher salivary NEFA concentrations than those without clinical symptoms (<i>n</i> = 6). Thus, BHB and NEFAs can be reliably measured in bovine saliva using easily automatable colorimetric methods. Salivary BHB increased in hyperketonemia and could be a potential biomarker of this condition. Further studies should be undertaken to clarify the mechanism and possible use of salivary NEFAs as biomarkers.