Holding on or heading up? The roosting preferences of brown- and white-feathered laying hen pullets

Although laying hens are known to be motivated to roost as high as possible and to use a perch that allows them to grasp, little is known about how these behaviours develop in young birds. We investigated relative preferences of laying hen pullets for roosting on round perches versus platforms and whether elevation affected their preference using three strain groups and two treatments over four periods of time. 120 DeKalb White and 120 Bovans Brown chicks were housed in groups of 10 in 24 floor pens, grouped as only white pullets (n = 8), only brown pullets (n = 8) or mixed strains (n = 8). Each pen was fitted with round metal perches (PERCH) and wire platforms (PLAT) installed on opposite sides of the pen, all accessible by wire ramps (RAMP). Over four 4-week long periods from 3 to 19WOA, platforms and perches were systematically offered in a manner such that the pullets were required to choose between type of structure versus elevation. In HiPlat treatment, PLAT was the highest available structure, and in HiPerch treatment, PERCH was the highest. Video recordings were used to count the number of birds on PERCH, PLAT, and RAMP. Images were taken of the pullets' feet grasping a perch starting at 6WOA to measure the average length of the pullet's foot wrapped around the perch. Overall, more birds chose to roost on PLAT than PERCH, and both were used more than RAMP. Brown-only pullets used the structures less than white. Structure use increased with age, with PLAT use highest at 12-14WOA, and PERCH use increasing at 16-18WOA. In HiPlat treatment more birds roosted on PLAT than PERCH whereas in HiPerch, birds were more evenly distributed between PLAT and PERCH. White birds had significantly longer feet than browns across all ages. Foot size was associated with the use of perches but not with use of platforms. Overall, pullets' preference for roosting on the platform outweighed their preference for elevation and for grasping a round perch. This suggests that elevated platforms are important structural elements for growing pullets.