Relative preference for different pecking blocks offered as pairwise comparisons in White and Brown-feathered laying hens

Different commercially available pecking blocks (PBs) have varying nutrient composition, appearance, and texture. However, the relative preferences of laying hens for different PBs are unknown. We housed 120 Dekalb White and 120 Bovans Brown in twelve (360 cm x 116 cm x 60 cm) test cages from 18 weeks of age. Test cages had two identical sections, each containing a nest, scratch mat, and container. Then, three PB types (A, B, C) were offered in a series of pairwise comparisons over three, 4-week periods (Phase 1). Pairwise comparisons were repeated over three, 2-week periods (Phase 2). Block A mainly comprised mineral + grains, B of mineral + grain + molasses, and C was primarily mineral based. PB use (disappearance) was measured by weekly weighing. Pecking and scratching behaviour was measured at the individual level by live observations of 7 focal birds (per cage) once a week (thrice daily). Behaviour at the group level was measured from video cameras mounted over each PB. The number of birds pecking or scratching at the blocks was counted every 5 minutes throughout the light period using instantaneous scan sampling (total = 169 scans/day, split into 3 times-of-day (TOD): a.m., mid-day, and p.m.). For phase 1, Browns used the B block more than any other block and strain combination (p < 0.0001). At group level, pair-wise comparison affected pecking or scratching behaviour (p < 0.05). In Whites (p = 0.04), the pair-wise comparison of blocks B and C resulted in more birds pecking or scratching at C. The opposite was observed in Browns, with more birds directing pecks or scratches at B (p = 0.01). Interactions were observed between the time-of-day and PB type (White: p < 0.0001, Brown: p = < 0.0001). The Whites pecked and scratched the C block at p.m. more than any other block at any other TOD. In the Browns, pecking or scratching was directed at the B block at mid-day and a.m. more than any other block at any TOD. The two common strains of laying hens in this study preferred different types of PB (Browns preferred B, Whites preferred C) and used them at different TOD. • Relative preferences for edible enrichments differed between strains of laying hens • The Brown strain of hens preferred a grain plus mineral-based pecking block • The White strain of hens preferred a mineral-based pecking block • Brown hens used blocks uniformly throughout the day • White hens used blocks most in the period before lights out