Effects of Stocking Rate and Environmental Enrichment on the Ontogeny of Pecking Behavior of Laying Hen Pullets Confined in Aviary Compartments during the First 4 Weeks of Life

Abstract

The objective of this study was to describe the ontogeny of the severe feather pecking (SFP), gentle feather pecking (GFP), aggressive pecking (AP), and enrichment pecking (EP) of non-beak-trimmed Lohmann Brown (LB)-pullets during the first 4 weeks of life (observation on 1st, 8th, 15th, 22nd, and 29th days of life) while they were kept within the compartments of a commercial rearing aviary (without access to a litter area). All chicks were placed into compartments of the middle tier of the aviary on the 1st day of life. On the 10th day of life, half of the chicks of each compartment were moved into the compartments of the lower tier. The aviary floor was covered with chick paper before the placement of the chicks and fully or partially removed from the 15th day of life onwards. The pecking behavior patterns were observed in three experimental groups (EG): NE (not enriched): group size until/after 10th day of life: 230/115; 120.8/60.4 birds/m2, no enrichment; EL (enriched, low stocking rate): group size until/after 10th day of life: 203/101, 106.6/53.6 birds/m2; and EH (enriched, high stocking rate): group size until/after 10th day of life: 230/115;120.8/60.4 birds/m2, both pecking stones and blocks as enrichment) in two rearing periods. For each pecking behavior pattern, an independent regression model with the parameters EG, chick paper, observation day, and functional area was estimated. GFP, SFP, and EP increased with age during the observation. The AP rate was highest in all EGs on the first day of life and decreased during the observation period. A pairwise comparison of NE (high stocking rate without enrichment) with EH (high stocking rate with enrichment and with EL (low stocking rate with enrichment) showed a significant effect of the EG on pecking behavior, with more SFP, AP, and GFP in NE. There were no differences between EL and EH, indicating that the provision of pecking materials had more influence than the stocking rate. However, we presumed that the difference between the stocking rates were too small to observe an effect. AP, SFP, and GFP were significantly higher on wired slats, as compared to the perches and the vicinity of the enrichment materials. The enrichment materials were suitable and intensely used by the pullets. The provision of pecking blocks and pecking stones was recommended as a preventive measure from the first day of life onwards for pullets housed in commercial rearing aviaries. There was no effect of reduced stocking rate, most likely due to the low variation in stocking rates.

Welfare of laying hens on farm

“…Beyond these first 4 weeks of life, there is some evidence of improved plumage condition in pullets reared at lower stocking densities. Bestman et al (2009) found that risk of plumage damage increased at more than 18 pullets/m 2 by the end of the rearing period, while Schwarzer et al (2022) found that the risk of plumage damage increased across the range of 11.9-31.6 pullets/m 2 of animal densities by end of rear. Nicol et al (1999) found significantly more gentle feather pecking at 30 birds/m2 than at lower densities of 22, 14 or 6 birds/m 2 .…”

“…(2009) found that risk of plumage damage increased at more than 18 pullets/m 2 by the end of the rearing period, while Schwarzer et al. (2022) found that the risk of plumage damage increased across the range of 11.9–31.6 pullets/m 2 of animal densities by end of rear. Nicol et al.…”

“…In a study of pullets kept in small experimental pens, locomotion at 15 weeks of age was significantly reduced from 1.79% of observation time when kept at 769 cm 2 /bird to just 0.37% of time when kept at 435 cm 2 (Hofmann et al., 2021). One study of pullets during their first 4 weeks in restricted compartments (effectively cages with no litter area) of a larger aviary system found that enrichment had more effect on the development of aggressive and feather pecking behaviour than the space allowance which varied between 94 and 83 cm 2 /bird to 10 days of age, and between 185 and 167 cm 2 /bird to 4 weeks of age (Schwarzer et al., 2022).…”

“…Chicks can be kept at high densities in the first 2 weeks of life (approximately 100–120 birds/m 2 ) which enables them to keep warm. No differences in plumage condition were noted when pullets were reared for the first 10 days of life at 107 vs 121 birds/m 2 or and between 54 and 60 birds/m 2 to 4 weeks of age (Schwarzer et al., 2022). Beyond these first 4 weeks of life, there is some evidence of improved plumage condition in pullets reared at lower stocking densities.…”