Plasma Serotonin in Laying Hens (Gallus gallus domesticus) With and Without Foot pad Dermatitis

The aim of this study was to investigate whether plasma serotonin (5-hydroxytryptamine [5-HT]) was associated with the presence of foot pad dermatitis (FPD) in laying hens. FPD birds (n = 20) and healthy individuals (n = 22) were included. Plasma 5-HT was investigated. FPD laying hens showed significantly higher 5-HT levels (median = 6 µmol/L) compared with healthy individuals (median = 4.28 µmol/L, P < .001). When present, FPD were scored as either 1 (n = 12) indicating mildly to moderately abnormal or 2 indicating severely abnormal (n = 8). The subjects whose lesions scored 2 had higher plasma 5-HT levels than those whose lesions scored 1. Inflammatory mechanisms seem to be related to plasma 5-HT levels in laying hens. Assessing plasma 5-HT could be useful to evaluate chicken welfare.