Abstract
At present, the assessment of pig welfare quality has gained significant importance, prompting the exploration of novel biomarkers for this purpose. Traditionally, these biomarkers have been monitored in the blood; however, blood sampling is considered an invasive procedure. Currently, non-invasive methods for collecting samples are emerging as viable alternatives for assessing these biomarkers. This article aims to present the current knowledge regarding the use of non-invasive methods for analysing pig welfare biomarkers, specifically focusing on the saliva, hair, faeces, and urine as matrices to determine these biomarkers. The saliva analysis encompasses various biomarkers, such as cortisol, alpha-amylase, chromogranin A, the total esterase, oxytocin, acute phase proteins, adenosine deaminase, immunoglobulins and parameters of redox homeostasis. Cortisol, a specific biomarker, can be determined in the hair, urine and faeces, while urine samples allow for the analysis of catecholamines as non-invasive markers of pig welfare.