Edible Environmental Enrichments in Littered Housing Systems: Do Their Effects on Integument Condition Differ Between Commercial Laying Hen Strains?

SIMPLE SUMMARY: Feather pecking can occur in laying hens. It is considered a behavioral disorder and can be triggered by a variety of factors. Feather pecking leads to plumage damage, which is detrimental to the welfare and performance of the animals. The behavior of allopecking is assigned to foraging and exploration behavior. Therefore, a possible approach to reduce feather pecking is to provide manipulatable, edible objects to direct the hens’ pecking to these substrates. Previous studies could not clearly answer the question of the effects of providing such environmental enrichment materials on plumage condition and performance. In order to clarify this question and investigate possible differences between different breeding lines, 4000 pullets were kept during rearing and 2808 hens were kept during the laying period with or without additional enrichment materials (pecking stones and alfalfa bales). The results showed that the effect of enrichment materials on plumage condition and also on pecking injuries of the skin differed between genetic strains. Therefore, the recommendations for the use of enrichment materials should be revised and specified for the hybrid lines. ABSTRACT: The aim of this study was to investigate the effect of additional enrichment materials (EMs; pecking stones and alfalfa bales) on the occurrence of plumage damage, skin injuries, and toe injuries, with an emphasis on the possible differences between commercial hybrid strains of laying hens. During rearing (weeks 1–18, 16 compartments, 4000 pullets) and laying periods (weeks 21–72, 24 compartments, 2808 hens) in a littered housing system, EMs were permanently provided to the study groups (EXP), while control groups (CON) did not receive additional EM. In a two-factorial study design (two groups with four strains) with 351 hens per variant, the brown egg-laying Lohmann Brown classic (LB) and Bovans Brown (BB) strains as well as the white egg-laying Lohmann Selected Leghorn classic (LSL) and Dekalb White (DW) strains were investigated. Compared to the CON, the EXP showed reduced body mass during rearing (p < 0.001) and reduced albumen consistency in the laying period (p < 0.001). Regarding integument condition, the LSL in the EXP showed more toe injuries than in the CON (p = 0.018). Remarkably, genotype-environment interactions between strains and groups were evident (p < 0.001). In groups with an EM supply, plumage damage decreased in LB (p ≤ 0.033) and LSL (p ≤ 0.005) but increased in BB (p ≤ 0.003). Moreover, there were fewer skin injuries in LSL (p = 0.001) but more in BB (p = 0.001) in groups with access to EM. In view of the diverging effects between strains, future practical recommendations for laying hen husbandry should be strain-specific.