Research note: Transient behavioral effects of feed restriction in a white feathered laying hen pullet strain - Assessment of frustration and locomotor energy expenditure.

Quantitative feed restriction is used to effectively manipulate layer pullet growth trajectories in research and rarely in commercial practice. In this study, we asked whether this intervention impairs pullet welfare or affects locomotor energy expenditure. Pullets were raised in furnished floor pens in a split-plot design: Two ages at photostimulation (18 weeks: early-PS vs 20 weeks: late-PS) with two feeding regimens each (ad libitum: AL vs 20%-restricted: R) between 12 and 21 weeks. Home pen video recordings were annotated for four behavioral categories: abnormal pecking, aggression, high-energy aerial locomotion, and low-energy locomotion via ramps. Feed restriction increased abnormal pecking behavior at 16, 17, and 18 weeks (P = 0.0002). Aggression increased during puberty, which occurred sooner for AL and early-PS than R and late-PS pullets, then decreased (P = 0.016). In R pullets, abnormal pecking tended to be higher, and aggression was higher post-meal than pre-meal (P = 0.06 and P = 0.006). No effect of restricted feeding was detected on high- and low-energy vertical locomotion (P = 0.954 and P = 0.268). These findings indicate that quantitative feed restriction of layer pullets can be used for research with appropriate caution, though potential effects on latent feather-pecking risk and late-life bone health should be considered.