Evaluation of a dustbathing substrate and straw bales as environmental enrichments in commercial broiler housing

The use of straw bales as an environmental enrichment is common for broiler chickens in enriched housing systems, however relatively little information exists about their effectiveness in improving welfare. There has also been no widespread introduction of a dustbathing material for broilers. The main aim of this trial was to evaluate the use of a dustbathing substrate (in the form of oat hulls), both as an alternative to straw bales and as a supplementary enrichment. Over four replicates, four commercial houses, each containing approximately 22,000 broilers, were assigned to one of four treatments over the 6-week production cycle: (1) straw bales (B; one per 155 m²), (2) oat hulls as a dustbathing substrate (OH; provided in 1 m diameter steel rings, one per 155 m²), (3) both oat hulls and straw bales (OH + B), and (4) a control treatment with no environmental enrichment (C). Observations of broiler behaviour and leg health were taken weekly, and performance data was collected for each cycle. Broilers housed in the OH and OH + B treatments had better gait scores in week 6 than those housed in the C treatment (P < 0.05), which suggests that the provision of oat hulls improved bird leg health. However, there was no associated increase in activity levels in unenriched areas of the houses. Conversely, more locomotion (P < 0.001), less sitting inactive (P < 0.001) and less sitting pecking (P < 0.001) were observed in the C treatment than in unenriched areas of B, OH and OH + B treatments. More birds were recorded around the bales compared to the oat hulls (P < 0.001), however birds performed significantly more foraging (P = 0.019) and dustbathing (P = 0.045) in oat hulls than around straw bales. Although oat hulls appear to be more suitable for stimulating active behaviours than straw bales, the high level of resting recorded around the bales suggests they may have a positive function as protective cover. The presence of an additional type of enrichment in the house did not affect the number of birds, or the type of behaviours performed in close proximity to either straw bales or oat hulls (P > 0.05). Treatment did not have a significant effect on pododermatitis levels or slaughter weight, on mortality rates, or on litter quality or atmospheric ammonia levels (P > 0.05). Overall, our results suggest that the oat hulls substrate was a successful enrichment in terms of promoting dustbathing and foraging, and improving bird leg health. The straw bales also appeared attractive to the birds, however, which suggests that a dustbathing substrate should be a supplementary enrichment.