Assessment of cortisol in swine by saliva:: new methodological approaches

The aim of this study was to compare the common method of saliva sampling with cotton buds to a new one. The advantage of this new method, called Oral Diffusion Sink (ODS) is the continuous measuring without any manipulation of the animals. During about 8 hours it is possible to accumulate steroids from saliva with a defined flow rate through the ODS. After alcohol extraction all samples were measured by a radioimmunoassay. Tn order to compare these two methods, the cortisol concentrations of the daily profile, as well as two defined stressors - social isolation and a 2-hours transport - were assessed in 10 German Landrace pigs. The daily hourly circadian rhythm measured in cotton buds showed significantly higher concentrations in the morning than in the evening (p=0.007). During social isolation significantly higher cortisol concentrations (p=0.009) and disintegration of the circadian rhythm could be observed in cotton buds, but not in ODS. Highest cortisol levels were found during transportation 60 min after loading (18.9 +/- 3.9 nmol/l). ODS samples correlated significantly with cotton bud samples taken quarterly (r=0.685; p=0.04). These results demonstrate that ODS may be a good method for a continuous monitoring of acute stress. Discrepancies in the daily cortisol profile and social isolation between concentrations of ODS and hourly taken cotton bud samples need to be clarified.