Research PaperEffects of horizontal distance between perches on perching behaviors of Lohmann Hens

•Perching behaviors of hens as affected by horizontal distance (HD) of perches were investigated.•HD of 25 cm seems to be the lower threshold for not restraining the hens' perching behaviors.•Hens display an interlaced perching pattern as HD approaches its lower threshold.•Hens tend to perch facing each other as HD approaches its lower threshold.•Hens showed most frequent perching activities during the dusk-simulating dim period.

Perching is a highly-motivated natural behavior of laying hens that has been considered as one of the essential welfare requirements. The objective of the study was to evaluate perching behaviors of laying hens as affected by horizontal distance (HD) between parallel perches. A total of 48 Lohmann white hens in three groups (16 hens/group) were used, 68 weeks of age at the experiment onset. For each group, hens were housed in an enriched wire-mesh floor pen (120 cm L × 120 cm W × 120 cm H) equipped with two round galvanized tube perches (120 cm long × 32 mm diameter, an average of 15 cm perch space/hen). HD was varied sequentially at 60, 40, 30, 25, 20 and 15 cm and then in reverse order. A real-time monitoring system was developed to continuously record hen's perching behaviors. The number or proportion of perching hens, perching duration, and perching trip and frequency were analyzed using an automated VBA (Visual Basic for Applications) program developed in Microsoft Excel. Heading direction of the perching hens and pattern of the perch occupancy were determined manually by video observation. Results showed that reduction of HD to 25 cm did not restrain hens' perching behaviors, whereas HD of 20 or 15 cm restrained perching to some extent. Specifically, at HD of 25 cm, hens perched interlacing with one another to maximize use of the perches during the dark period. As a result, the proportion of perching hens and perching duration for HD of 25 cm were not reduced as compared to HD of 30-60 cm. However, the proportion of perching hens was significantly reduced at HD of 15 cm (P = 0.001-0.025). HD of 15 and 20 cm also significantly reduced daily perching time of the hens. In contrast, perching trip or frequency and heading direction of the perching hens were not influenced by HD (15-40 cm) except for HD of 60 cm. The results suggest that although 30 cm is the recommended minimum HD, 25 cm may be considered for situations where additonal perches are necessary to meet all hens' perching needs.