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Cortisol/Dehydroepiandrosterone ratio in saliva: endocrine biomarker for chronic stress in pigs?

Fels, Michaela, Rauterberg, Sally, Schwennen, Cornelia, Ligges, Uwe, Herbrandt, Swetlana, Kemper, Nicole, Schmicke, Marion
Livestock science 2019
animal welfare, biomarkers, blood serum, cortisol, farms, piglets, prasterone, rearing, saliva, straw, tail docking
The adrenal hormone dehydroepiandrosterone (DHEA) in contrast to cortisol is suggested as a chronic stress marker. The aim of the present orientation study was to test whether DHEA was different in 10-wk-old pigs reared with three different housing systems on different farms. Blood and saliva were taken from 71 pigs reared under either indoor conditions with low disease level (n=30; I+) or indoor conditions with different welfare and health problems (caudophagia, infections, I-; n=21) or under improved conditions (combination of indoor and outdoor areas, C; n=20), aimed to enhance animal welfare, for instance by offering straw and abandonment of tail docking. In C pigs, serum cortisol was lower than in I+ (p<0.001), but similar to I-. In saliva, cortisol levels in pigs from C were lower compared to I+ and I- (P<0.001). Serum DHEA was lower in C pigs than in I- pigs (P=0.017) and in I- pigs it was higher compared to pigs reared under I+ conditions (P<0.001). DHEA in saliva was higher in pigs from C compared to I+ pigs and I- pigs (P<0.001). In saliva, the piglets reared in C showed a lower cortisol/DHEA ratio compared to I+ pigs and I- pigs (P<0.001) which may indicate less stressors in the C system. Further research is needed to confirm these results and to show the importance of DHEA for the analysis of chronic stress in pigs.