Laying hens' preferences for nest surface type are affected by enclosure

The nest surfaces preferred by hens are inconsistent with those typically provided in commercial settings. However, little research has explored hens' preferences for commercially available nest surfaces. Our objective was to compare hens' preferences for two such surfaces - red smooth and yellow mesh plastic- either enclosed or unenclosed with curtains. We predicted that enclosed nests would be preferred, but that this may be offset by any preferences hens have for different surface types. After conventional rearing, 996 pullets were placed in 24 furnished cages (FC) at 15 weeks of age (large: 41,296 cm2; small: 20,880 cm2). In Phase 1, each FC had two nests, one with a yellow mesh plastic surface and one with a red smooth plastic surface (3368 cm2). In half of the FCs, both surfaces were enclosed with plastic red curtains (ENCL, n = 12). The remainder had both open surfaces (OPEN, n = 12). In Phase 2, all FCs were subsequently modified at week 28 to have one enclosed and one open surface, allowing us to titrate how much hens preferred surface against enclosure. Preference was inferred from where eggs were laid, the location of sitting, and the amount of time spent on each surface. Egg location was recorded from the first egg to week 36. Sitting behaviour was scan sampled during weeks 25-26 (Phase 1) and 34-35 (Phase 2). Focal hens were selected at week 20 and observed from week 22-24 (Phase 1) and 31-33 (Phase 2). Results were unexpected: in Phase 1, hens laid more eggs on red smooth mats than yellow mesh when they were OPEN (66.8 ± 1.8% vs. 31.2 ± 1.8%; P < 0.0001), but more on yellow mesh mats than red smooth if they were ENCL (62.1 ± 2.1% vs. 36.7 ± 2.1%; P < 0.0001). In Phase 2, when all FCs had one open and one enclosed nest, hens preferred to lay in the enclosed nest (59.5 ± 2.0% vs. 39.5 ± 1.9%; P < 0.0001) but more so if they also had previous experience of an enclosed nest (P < 0.0001). In Phase 2, individual hen behaviour did not show that one surface was preferred over the other, but did indicate preference for enclosure. Hens changed their preferred nesting site from Phase 1 when enclosure was modified to favour the enclosed nests. This demonstrates that nest enclosure is important regardless of surface or hens' previous experiences, and that preference for a commercial nest surface depends on whether it is enclosed.