Steroids in pig hair and welfare evaluation systems: combined approaches to improve management in pig breeding?

The aim of the present pilot study was to determine the allostatic load by analysing the hair cortisol and dehydroepiandrosterone‑sulphate (DHEA‑S) of commercial pigs belonging to different farms having good overall animal welfare according to the CREnBA (Centro di Referenza Nazionale per il Benessere Animale - Brescia, Italy) assessment protocol. The study was conducted on 86 pigs belonging to three farms with a grade higher than 8 on the CReNBA welfare evaluation system. Hair samples were taken by shaving on sows 1‑10 days after weaning (Farms 1 and 2) and at the age of 8‑10 months (Farm 3). The hormone concentrations were measured by radioimmunoassay. From the box plots, it is evident that the hair cortisol concentrations of animals were different between farms. Conversely, the variability of the hair DHEA‑S concentration was similar between the F1 and F2 farms but much lower at F3. For all the variables considered (cortisol, DHEA‑S and cortisol/DHEA‑S ratio), F2 showed a higher hair concentration level than F1 (P < 0.05). The study's results indicate that the measurement of cortisol and DHEA‑S in pig hair shows a different allostatic load between them, although the official welfare evaluation method assessed the farms as having good overall animal welfare.