Acute phase proteins as biomarkers of pre-slaughter stress in pigs
Pre-slaughter handling, which include transportation, housing, social stress, heat, and dietary changes, is one of the main causes that produces stress in pigs. The appropriate biomarkers and objective laboratory criteria to evaluate pre-slaughter stress are lacking. Behavioral and physiological markers are commonly used for this reason, but these parameters may increase for reasons unrelated to stress. Acute phase proteins are considered to be markers of inflammation that have been proposed as indicators for farm animal stress monitoring. The major acute phase proteins in swine are haptoglobin, serum amyloid A, c-reactive protein, and pig major acute phase protein. Serum or plasma obtained from blood are the most used matrixes for the measurement of acute phase proteins, the collection of which involves an invasive collection method that is harmful and stressing. The use of saliva and meat juice instead of blood might overcome these disadvantages, since its collection is non-invasive and stress-free. For any assay measuring acute phase proteins, adequate analytical validation must be performed, as well as harmonization and standardization of analytical procedures. The aim of this paper is to emphasize the possibilities of use of acute phase proteins as biomarkers of pre-slaughter stress, as well as to provide survey of methodologic assays and fluids that are presently available to measure acute phase proteins.