Chromogranin A and S100A12 protein measurement in hair of pigs: assay validation, changes across different production stages and comparison with other hair biomarkers.

Hair has emerged as a non-invasive matrix for retrospective assessment of health status in pigs. While hair cortisol and sulphate dehydroepiandrosterone (DHEA-S) have been used as biomarkers of the hypothalamic-pituitary-adrenal (HPA) axis, indicators of the sympathetic-adrenomedullary (SAM) axis and innate immunity, such as chromogranin A (CgA) and S100A12, have not yet been measured in hair. This study aimed to (1) evaluate if CgA and S100A12 could be detected in pig hair, and (2) analyse possible longitudinal changes in their concentration across key production stages of growing pigs (lactation, nursery, and fattening in 20 pigs sampled longitudinally) and compare their values with cortisol and DHEA-S. For CgA and S100A12 measurements, AlphaLisa technology was used, while cortisol and DHEA-S were quantified using an automated chemiluminescence assay. Validation showed the immunoreactive detectability of CgA and S100A12 in hair extracts, with a high precision (CVs < 15%), linearity after serial sample dilution (R2 = 0.99), and adequate recovery (94.1-109.1%). During a productive cycle in fattening pigs, CgA concentrations increased progressively throughout the cycle, having higher values at the end of the fattening period (p=0.022), while S100A12 concentrations peaked significantly at the end of nursery (p = 0.0004). . Cortisol was highest at end of nursery, whereas DHEA-S increased significantly at the end offattening (p = 0.0002). This report provides evidence for the immunoreactive detectability of CgA and S100A12 in pig hair extracts, opening a new window into the potential evaluation of these analytes in this matrix.