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Even though aviary systems provide a range of benefits for laying hens in terms of animal welfare, falls and collisions have been observed in experimental settings. These falls are likely stressful for the birds and are thought to be linked to the known high prevalence of keel bone fractures in aviary-housed hens. We investigated the frequency of falls and fall patterns such as collisions, height and cause of fall as well as the prevalence of keel bone damage in commercial aviary-housed Swiss layer flocks and the relationship with time of day and week of age. We also examined the effect of a prolonged artificial dusk length on the number of falls. In total, eight commercial Swiss laying hen farms with two barns each were used and dusk length was adjusted to vary continuously between 14 and 76 min over all 16 barns. Video recordings and palpation of the keel bone to assess fractures, deviations and alterations of 100 hens per flock were conducted in week of age (WOA) 20 and 45. Videos were analysed after lights on, at mid-day, during the whole dusk phase as well as after lights off. Statistical analyses were conducted using generalized as well as linear mixed-effects models. Fall frequency was highest during the dusk phase in WOA 20 compared with any other observed times of day and WOA 45 (all combinations: p |
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