Holt, R. V., Vas, J., Vasdal, G. et al. 2023. A buffet of litters – Broiler chickens behave differently according to litter type and freshness. Applied Animal Behaviour Science 260, 105856.

Poultry are usually provided with a single litter type that may not satisfy all litter-directed behavioural functions and may lose functional value over time due to soiling and degradation. We investigated this hypothesis in two commercial broiler flocks reared to 34 days of age on peat litter. We provided “litter buffets” comprising seven adjacent 1-m2 litter trays, each containing a different litter type (peat, peat mixed with sawdust, wood shavings, finely-chopped bark, oat straw pellets, coarsely-crushed rape straw, and finely-ground rape straw), in two different locations of the house. We observed the number of chickens performing different behaviours, and total number present, in each litter tray once weekly for four weeks, before and after adding 5 L of fresh material. The litter types varied in attractiveness for ground scratching (an exploratory component of foraging behaviour; P < 0.001), with the most ground scratching occurring in peat, mixed peat, wood shavings, and fine straw (in order of preference). More ground scratching also occurred in fresh than used litter (P < 0.001). Dustbathing varied according to the interaction between litter type and freshness (P = 0.029), with mixed peat, peat, fine straw, and wood shavings being preferred when fresh, and fine straw best retaining dustbathing attractiveness when used. Lying resting varied between litter types (P < 0.001), being highest in wood shavings, mixed peat, and fine straw regardless of freshness and, because lying resting was the most common activity, the total chickens present followed the same pattern. The proportion of small particles (≤1.0 mm diameter) increased to varying extents between litter types as litter degraded from fresh to used. Ground scratching was not associated with particle size distribution. However, chickens preferred to dustbathe in fresh litter with more small particles (P < 0.001), and in used litter with fewer large particles (>3.6 mm; P = 0.023). They also tended to avoid lying resting in fresh litter with a high proportion of large particles (P < 0.001). Consistent with our hypothesis, different litter materials stimulated different behavioural responses and top dressing with fresh litter increased litter attractiveness for ground scratching and dustbathing. We conclude that broiler welfare can be improved by providing a choice of litter materials to address different motivational priorities. Although chickens were attracted to peat and mixed peat for ground scratching and dustbathing, to avoid loss of peatlands (an environmental sustainability concern), wood shavings can be the main litter type, supplemented by patches of fine rape straw, with periodic top dressing of both.