Keel bone fractures induce a depressive-like state in laying hens

Elena Armstrong*, Cristina Rufener, Michael Toscano, J Eastham, J Guy, V Sandilands, Tim Boswell, Tom Smulders

*Corresponding author for this work

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Abstract

In commercial flocks of laying hens, keel bone fractures (KBFs) are prevalent and associated with behavioural indicators of pain. However, whether their impact is severe enough to induce a depressive-like state of chronic stress is unknown. As chronic stress downregulates adult hippocampal neurogenesis (AHN) in mammals and birds, we employ this measure as a neural biomarker of subjective welfare state. Radiographs obtained longitudinally from Lohmann Brown laying hens housed in a commercial multi-tier aviary were used to score the severity of naturally-occurring KBFs between the ages of 21–62 weeks. Individual birds’ transitions between aviary zones were also recorded. Focal hens with severe KBFs at 3–4 weeks prior to sampling (n = 15) had lower densities of immature doublecortin-positive (DCX +) multipolar and bipolar neurons in the hippocampal formation than focal hens with minimal fractures (n = 9). KBF severity scores at this time also negatively predicted DCX + cell numbers on an individual level, while hens that acquired fractures earlier in their lives had fewer DCX + neurons in the caudal hippocampal formation. Activity levels 3–4 weeks prior to sampling were not associated with AHN. KBFs thus lead to a negative affective state lasting at least 3–4 weeks, and management steps to reduce their occurrence are likely to have significant welfare benefits.

Original languageEnglish
Article number3007
JournalScientific Reports
Volume10
Early online date20 Feb 2020
DOIs
Publication statusFirst published - 20 Feb 2020

Keywords

  • hippocampal formation
  • avian brain
  • adult neurogenesis
  • chronic stress
  • keel bone damage
  • animal welfare
  • Gallus domesticus

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    Armstrong, E., Rufener, C., Toscano, M., Eastham, J., Guy, J., Sandilands, V., Boswell, T., & Smulders, T. (2020). Keel bone fractures induce a depressive-like state in laying hens. Scientific Reports, 10, [3007]. https://doi.org/10.1038/s41598-020-59940-1