Almond shells as environmental enrichment for laying hens: Implications for welfare and egg quality

Environmental enrichment is a promising strategy to improve welfare in laying hens, particularly in aviary systems where large group sizes and complex social interactions can predispose birds to fearfulness and feather pecking. This study evaluated the effects of providing coarsely milled almond shells (AS; geometric mean diameter = 1525 µm) as an environmental enrichment on welfare indicators, egg quality, and organ development in large commercial aviary flocks. The study compared two treatments-hens receiving AS and a control group that did not receive AS-with four pens per treatment and 2,500 hens per pen. Welfare indicators, as well as external and internal egg quality traits, were assessed at peak lay (13 weeks (wk) of trial; 33 weeks of age) and post-peak lay (23 wk of trial; 43 wk of age). In addition, at 23 wk of trial, serum corticosterone and relative organ weights were measured. At peak lay, hens provided with AS enrichment showed reduced fearfulness in the novel object test (P < 0.001), a trend toward lower gentle feather pecking (P < 0.1), and fewer comb pecking wounds and lower overall pecking scores (P < 0.001). No differences were observed in free feathers in the litter or severe/aggressive pecking. At post-peak, hens provided with AS enrichment continued to show lower fear responses (P < 0.001), fewer free feathers in the litter (P < 0.05), and tendencies toward reduced plumage damage, lower overall pecking scores, and reduced serum corticosterone (7.05 vs. 11.23 ng/mL; P < 0.1). Both internal and external egg quality parameters remained unaffected at both ages. Relative weights of liver, proventriculus, gizzard, pancreas, and spleen were unchanged, while small and large intestines tended to be heavier in hens provided with AS enrichment (P < 0.1). In conclusion, milled AS could be an effective enrichment for aviary-housed laying hens, by reducing fear and stress, mitigating feather pecking, and supporting minor digestive adaptations, without compromising egg quality. These findings support the use of AS as a sustainable agricultural by-product to improve welfare in large commercial flocks.