Zepp, M., Louton, H., Erhard, M. et al. 2018. The influence of stocking density and enrichment on the occurrence of feather pecking and aggressive pecking behavior in laying hen chicks. Journal of Veterinary Behavior 24, 9-18.
The housing conditions and environments experienced during the rearing period can influence the development of feather pecking in chickens during this time and in the subsequent laying period. The aim of this study was to investigate the effect of a reduced stocking density and the provision of enrichment materials on the occurrence of feather pecking in hen chicks under commercial rearing conditions. Three groups, identical in age, laying strain, and management but kept with different stocking densities and varying availability of enrichment (pecking stone, pecking block, and lucerne bale), were observed. Group 1 had a high stocking density (22.9 animals per m2) and no access to enrichment, group 2 had a lower stocking density (18.1 animals per m2) plus enrichment, and group 3 had a high stocking density (22.9 animals per m2) plus the same enrichment as group 2. Behavioral observations from video recordings were made on the occurrence of enrichment pecking, gentle feather pecking (GFP), severe feather pecking (SFP), and aggressive pecking. Furthermore, the influence of enrichment pecking on the occurrence of GFP, SFP, and aggressive pecking and the effect of SFP on the plumage condition were examined. The comparison of the 2 groups with enrichment demonstrated that the group with the higher stocking density showed a higher rate of SFP (95% confidence interval [CI] for the difference: [0.001-0.015]). The comparison of the 2 groups with and without enrichment but with equal stocking densities showed that the group with access to enrichment had significantly lower rates of GFP (95% CI: −0.019 to −0.006), SFP (95% CI: −0.036 to −0.020), and aggressive pecking (95% CI: −0.004 to −0.001). The group with a combination of a lower stocking density and enrichment had significantly lower rates of GFP (95% CI: −0.022 to −0.009), SFP (95% CI: −0.044 to −0.028), and aggressive pecking (95% CI: −0.004 to −0.001) compared to the group with a high stocking density without enrichment. Additionally, the occurrence of enrichment pecking had a significantly reducing effect on the occurrence of GFP (95% CI: −0.046 to −0.031), SFP (95% CI: −0.030 to −0.016), and aggressive pecking (95% CI: −0.003 to −0.0003). Finally, a high rate of SFP had a deteriorating effect on the plumage condition (95% CI: −0.859 to −0.084). Thus, we conclude that a lower stocking density and the provision of enrichment, such as pecking stones, pecking blocks, and lucerne bales, can reduce the prevalence of feather pecking and aggressive pecking in laying hen chicks. The evaluation of the plumage condition can be a valid indicator of feather pecking.