This is the way: The effect of artificial cues on early life ramp use behaviour of laying hen chicks

Abstract

Providing laying hen chicks with ramps during the rearing phase has been shown to increase inter-tiers transitions and use of elevated surfaces within aviaries. To maximize these benefits, we aimed to investigate if artificial cues that utilize the behavioural predispositions of domestic chicks would increase ramp use during the rearing phase and whether this increase would benefit the birds by improving their spatial cognition and skeletal strength. For this, we conducted two experiments: E1 compared two light cues (Dotter and Flicker) and E2 three moving cues (Beak, Hen, and LED) with respective control groups. Identical pens with two vertically stacked tiers connected by two ramps that housed 22 LSL chicks each were used for both experiments (N = 4/treatment). Cues were applied in intermittent bouts spread throughout the day until 60 days of age (DoA). We counted the number of inter-tier transitions using ramps, as well as the active use of ramps (e.g., walk/run, jump) that did not result in a transition by scan sampling recorded videos both when the cues were on and off. In E1, 47 birds (N = ∼12/treatment) underwent a spatial cognition test during 64 – 75 DoA and biomechanical properties of the tibiae and humeri were assessed for 20 birds per treatment by performing a three-point bending test at 87 DoA. Generalized linear mixed model analysis for E1, revealed that birds from both light cue groups performed more transitions when the cues were on compared to when the cues were off (χ2 = 6.18, p = 0.03). A three-way interaction between treatment, cue status, and DoA was found for active use of ramps (χ2 = 5.19, p = 0.02) with birds performing more active behaviours on ramps when cues were on compared to when cues were off until 38 and 24 DoA for Dotter and Flicker treatments, respectively. No differences between light cues and control groups were found in bone biomechanical properties and spatial cognition. In E2, birds from the Beak treatment performed 1.5 times fewer transitions than the Control birds (χ2 = 10.16, p = 0.02). Active use of ramps was affected by an interaction between treatment and DoA (χ2 = 13.33, p < 0.01) with birds from LED groups performing more active behaviours with increasing age while it decreased in the Hen and Control group groups. Overall, birds were more responsive to the cues that utilized predispositions based on the foraging aspects than the cues based on predispositions that aided in social interactions.