Navigation ability of White and Brown hens in an aviary system during laying phase

In cage-free systems, perches allow birds to exercise and to use the vertical space, therefore improving animal distribution. However, hen navigation in the complex aviary environment could result in failed landings and collisions, which could be influenced by genotype and aviary design. We tested the hypothesis that increased perch availability could improve the navigation ability of hens of different genotypes during the laying phase. To this scope, we monitored 1,800 hens (from 28 to 39 weeks of age) housed in a multi-tier aviary system and distributed in 8 pens (225 hens/pen) according to a bi-factorial design with two genotypes (Lohmann White vs. Hyline Brown) and two types of pens (enriched or not with additional perches). In the enriched pens, 6 additional perches (1.20 m long), were placed at the outer net walls and at different heights (0.30, 0.90, and 1.50 m on the left side; 0.60, 1.20 m, and 1.80 m on the right side). Hen movements were video-recorded at 28, 32, 36, and 39 weeks of age, and the number and rate of successful landings on the ground and take-offs to the aviary were scored every 10 min/hour (9:00 to 21:00). Observations were categorized into four periods throughout the day: early hours (5:00 to 08:00), morning (9:00 to 12:00), afternoon (13:00 to 16:00), and evening (17:00 to 21:00). Landings decreased from 28 and 32 weeks to 36 and 39 weeks of age (88 to 78 events per observation hour; P<0.05). The rate of successful landings did not change with age (96.0%, on average), being the highest at early day hours compared with the other periods (99.4% vs. 94.7%; P<0.001). White hens showed a 2.5-fold number of landings per observation hour (119 vs. 48; P<0.001) with a higher successful rate (+2%; P<0.001) compared with brown hens, whereas the presence of additional perches affected neither the number of landings nor their successful rate. Take-offs number (56 events per observation hour, on average) and their successful rate (99.8%, on average) did not change with age. The number of take-off was 3.3-fold in White compared to Brown hens (87 vs. 26 events per observation hour; P<0.001) and 9.3% higher in the pens with additional perches compared to pens without (P<0.05), whereas their successful rate was similar among groups. In conclusion, the navigation ability of hens during the laying period was more influenced by genotype and period of the day rather than by hen age or the presence of additional perches in the aviary.