Different chick processing holding devices reveal welfare and stress effects via novel down-feather biomarkers

Infrared beak treatment (IRBT) and s.c. vaccinations are often performed on the Poultry Services Processor (PSP) or Hatchling Support System (HSS). The PSP includes a holding device (HD) where the jaw rests and plastic 'feet' close around the head. The HSS has a modified HD, reduced feet load station pressure, and cradle for body support. The original feet design (F1) was amended for increased head space (F2), and they are interchangeable between HD types. This study tested three HD configurations (treatments (trt)): PSP with F1 (PSP-F1), PSP with F2 (PSP-F2), or HSS with F2 (HSS-F2) at a commercial hatchery. Chicks (120 Lohmann LSL-Lite (W) and 120 Lohmann Brown (B)) underwent standard processing before trt. To isolate HD effects, birds were not IRBT or vaccinated. Heart rate was tested pre- and post-trt. Surface body temperature (SBT), tonic immobility, and disorientation were measured post-trt. Blood was collected post-trt, chicks were euthanized, and down feathers collected to assess heat shock proteins (HSP60, 70, 90), tumor necrosis factor alpha (TNFα), C-reactive protein (CRP), and Transient Receptor Potential Vanilloid 4 (TRPV4) mRNA expression via real-time quantitative PCR. The M. complexus and fascia at the occipital crest were scored for bruising. Data were analyzed as a 2 × 3 factorial arrangement with a two-way ANOVA. Heart rate did not differ between HD or strain. Chicks in W-PSP-F1 were more disoriented than all strain-HD trt, and PSP-F1 were more fearful and had the lowest SBT. Head bruising was highest on W chick M. complexus and B chick fascia. In down feathers, HSP60 was higher in PSP-F2 vs PSP-F1; HSP70 was highest in B vs W chicks. TNFα expression was higher in W-PSP-F1 and W-PSP-F2 than W-HSS-F2. Blood biomarkers, except HSP70, demonstrated interactions between HD and strain. The HSS-F2 resulted in improved welfare, and data suggest that adjustments be made for chick head size differences. This study is the first to identify a non-invasive method for measuring stress and inflammatory biomarkers in chick down feathers.