Evaluation of Fear and Stress in White Layers Housed in Either Conventional Cages or Enriched Colony Cage
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2017 G.S. Archer et al. Background and Objective: The US egg industry is currently moving away from conventional cage housing towards larger colony caging systems. However the most common breed in the U.S.A., the Hy-Line W-36, has been selected based on conventional housing systems. The present study was designed to investigate the effect of housing hens in colony systems on the stress and fear response. Methodology: W-36 pullets were housed in either enriched colony (EC) system or conventional A-frame cages, with manure shields (CC), from 23-79 weeks of age. Plasma corticosterone (CORT, n = 60) and composite physical asymmetry (ASYM, n = 60) were used to evaluate the stress response. Tonic immobility (TI, n = 60) and inversion (INV, n = 60) were used to determine fear. Measurements were done at 23 week of age (T1), 33 week of age (T2), 56 week of age (T3) and 79 week of age (T4). Results: No differences were observed (p>0.05) in CORT (20.88.6 ng mL-1), ASYM (1.870.13 mm), latency to right during T1 testing (259.316.5 sec), or intensity of flapping during INV (4.20.2 flaps/sec) at 23 weeks of age. The EC and CC differed in CORT at T2 (p = 0.02), T3 (p = 0.03) and T4 (p = 0.04). Similarly, EC and CC differed in ASYM at T2 (p = 0.004), T3 (p = 0.03) and T4 (p = 0.05). While no difference (p>0.05) was still observed in the latency to right during T1 at T2 (284.519.1 sec) or T3 (284.519.1 sec) the EC did differ from the CC at T4 (p = 0.02). The EC also flapped more intensely during INV in T2 (p<0.001), T3 (p<0.001) and T4 (p<0.001). Conclusion: This indicates that the EC were more stressed and were more flighty than CC. Furthermore, it appears that housing W-36 Leghorns in enriched colony systems may not be desirable over conventional cages based on these results.