Space Allowance of the Littered Area Affects Lying Behavior in Group-Housed Horses.
Authors: Burla Joan-Bryce, Rufener Christina, Bachmann Iris, Gygax Lorenz, Patt Antonia, Hillmann Edna
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: Space Allowance of the Littered Area Affects Lying Behavior in Group-Housed Horses Group-housed horses require adequate lying space to achieve essential REM sleep, which demands recumbency for a minimum of 30 minutes daily, yet the optimal dimensions for shared littered areas remain contested—prompting this Swiss research team to systematically evaluate how different bedding area allowances influence lying behaviour in eight groups of 38 horses across four treatment conditions. Over an 11-day exposure to each condition (ranging from no litter provision through to 1.5 times the legal minimum dimensions), researchers documented lying patterns during the final 72 hours, revealing that whilst total daily recumbency duration increased progressively with larger littered areas, the relationship was not linear: high-ranking horses showed diminishing returns beyond minimal legal dimensions, whereas subordinate animals continued to benefit from expanded space. Critically, low-ranking horses experienced significantly fewer forcibly interrupted lying bouts when allocated 1.5 times the minimum area rather than 0.5 or 1.0 times, underscoring the social competition for this resource; despite this improvement, some individuals still failed to achieve the 30-minute daily recumbency threshold even in the most generous allocation. The absence of soft, deformable bedding entirely eliminated recumbency in most horses, confirming that surface quality is non-negotiable alongside spatial provision. These findings suggest that current Swiss animal welfare legislation stipulating minimal littered dimensions may prove insufficient for subordinate horses within a group, with practitioners managing group-housed stock needing to consider both absolute space provision and the social hierarchy's influence on individual access to adequate REM sleep opportunities.
Read the full abstract on PubMed
Practical Takeaways
- •Litter provision is non-negotiable for lying behavior—hard surfaces alone are insufficient; horses must have access to soft, deformable bedding to lie down comfortably
- •Current Swiss minimum space requirements for littered areas are inadequate for subordinate horses in groups; increasing litter area to 1.5× minimum significantly improves welfare for lower-ranking individuals who are otherwise displaced
- •Monitor individual horses in your groups for adequate recumbency; some horses may still fail to achieve necessary REM sleep even with compliant facilities, suggesting management of group dynamics or individual housing may be needed for certain animals
Key Findings
- •Horses provided with no litter (T0) showed severely restricted recumbency with majority lying <30 min/24h, compared to littered treatments (p=0.0006)
- •Total recumbency duration increased with larger littered area dimensions, with effect plateauing in high-ranking horses at 1.5× minimal dimensions but continuing in low-ranking horses (p=0.076)
- •Low-ranking horses experienced significantly more forcedly terminated lying bouts in T0.5 and T1 treatments compared to high-ranking horses, but this difference disappeared at T1.5 (p=0.005)
- •Even at 1.5× minimal legal dimensions, some individual horses failed to achieve the 30-minute minimum recumbency required for REM sleep