The aim of the current study was to validate an automated spectrophotometric method for salivary alpha-amylase measurement in pigs and evaluate its possible application as a noninvasive stress biomarker. The analytical validation included intra- and interassay precision, linearity under dilution, and limit of detection. In addition, to study the possible use of salivary alpha-amylase as a possible stress marker, 12 crossbred growing pigs of 3–4 months of age were subjected to restraint stress by a nasal snare for at least 1 min, and saliva samples were obtained at different time points. The results of analytical validation indicated that the method was precise and able to measure alpha-amylase in a linear manner. The results obtained in the stress test showed a significant increase in salivary alpha-amylase activity. Although other factors influencing this enzyme activity should be studied, these preliminary results indicate that salivary alpha-amylase could be a reliable biomarker of stress in pigs.

The objective of this study was to develop and validate a time-resolved immunofluorometric assay (TR-IFMA) for porcine salivary chromogranin A (CgA) measurements, using a species-specific antibody, and evaluate its behaviour in an acute stress model. Polyclonal antibodies were produced in rabbits immunized with a synthetic porcine fragment of CgA359-379 and used to develop a sandwich TR-IFMA. This TR-IFMA was analytically validated and showed intra- and inter-assay coefficients of variation of 6.23% and 5.82%, respectively, an analytical limit of detection of 4.27 × 10-3 μg/ml and a limit of quantification of 24.5 × 10-3 μg/ml. The assay also demonstrated a high level of accuracy, as determined by linearity under dilution (r = 0.975) and recovery tests. When a model of experimental acute stress, in which animals were immobilized for 3 min with a nose snare (stressor stimulus), was applied, a significant increase (P < 0.05) in CgA levels in saliva was detected at 15 min post-stressor stimulus. These results indicate that the assay developed in this study could measure CgA in porcine saliva in a reliable way and that the concentrations of CgA in saliva samples of pigs increase after an acute stress situation.