Abstract
Piling, a behaviour where hens crowd together, is referred to as smothering if mortalities result. Smothering is a considerable concern for the egg industry, yet is vastly understudied. During an outbreak of recurrent smothering, continuous video footage captured a commercial, free-range flock over 35 days. We describe the piling behaviour observed and potential associations with productivity and flock health indicators. Forty-eight piles were filmed, with a maximum density of 187.93 birds/m2 and up to 1204 birds in one pile. Piling occurred in the same house location on 33 of 34 observation days, the first evidence of regularity in piling behaviour. Despite extreme bird densities, we did not find associations between piling extremity and productivity but did find associations with water:feed ratio and temperature range. This study describes the most extreme level of piling reported in literature and offers new insights into this problem behaviour and its consequences.
Highlights
Smothering, poultry crowding together causing mortality, is a major economic and welfare concern for the egg-laying industry.[1,2,3] We estimate the UK egg industry loses £6.5 million/year due to smothering
Inter-rater reliability was satisfactory: the intraclass correlation coefficient (ICC) was 0.98 for counts of hens a priori based on 14 observations and 224 grid squares counted by two observers; ICC3 was 0.90 for peak pile time; and weighted kappa was 0.70 for the pile rating (∼10% of piling events scored by two observers from videos cropped to the event, 409 data points in total)
Contrary to research describing recurrent piling as unpredictable,[1,2,3,5] piling in this flock occurred at a predictable time
Summary
Smothering, poultry crowding together causing mortality, is a major economic and welfare concern for the egg-laying industry.[1,2,3] We estimate the UK egg industry loses £6.5 million/year due to smothering (based on mortality rates from 1). This figure does not account for the previously unconsidered effects of sublethal injuries or flock stress, such as bone fractures, heat stress, and the stress of physical restraint. Methods: During an outbreak of recurrent smothering, continuous video footage captured a commercial, free-range flock over 35 days. Conclusion: This study describes the most extreme level of piling reported in literature and offers new insights into this problem behaviour and its consequences
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