Asia Pacific Centre for Animal Health, Melbourne Veterinary School, Faculty of Science, The University of Melbourne, Parkville 3010, Victoria, Australia.
Animal Welfare Science Centre, Melbourne Veterinary School, Faculty of Science, The University of Melbourne, Parkville 3010, Victoria, Australia.
Prev Vet Med. 2024 Feb;223:106098. doi: 10.1016/j.prevetmed.2023.106098. Epub 2023 Dec 21.
Since the early 2000 s the practice of free-range egg production has increased in developed countries, partly driven by consumer perception that free-range housing is better for hen welfare. While poultry in free-range systems have more behavioural opportunities compared with poultry in caged systems, free-range systems are associated with greater frequencies of infectious disease, predation and 'smothering', a condition where birds pile on top of one another with death occurring due to suffocation. Although the frequency of smothering deaths in Australian free-range layer poultry is anecdotally high, there is a lack of empirical evidence quantifying smothering cause-specific mortality rates and identifying factors that place birds at higher risk of death from smothering. This was a prospective cohort study of poultry flocks managed by three commercial free-range layer organisations in Eastern Australia. Flocks were enrolled into the study from 1 January 2019 to 29 March 2021 and were followed until the end of lay or until the end of the study on 31 March 2022, whichever occurred first. Throughout the follow-up period flock managers provided production details for each flock and details of smothering events using custom-designed logbooks.A total of 84 flocks were enrolled in the study: 32 from Organisation 1, 35 from Organisation 2 and 17 from Organisation 3. The number of birds per flock ranged from 16,000 to 45,000. The total mortality rate was 1131 deaths per 10,000 bird-years. Smothering mortality rate across the three organisations was 183 (minimum 133, maximum 223) deaths per 10,000 bird-years at risk. Smothering accounted for around 16% (minimum 9%, maximum 22%) of all deaths.We identified no distinctive temporal pattern in daily smothering risk as a function of either the number of days since placement or calendar date. The locations of smothering events in sheds and in the outdoor range were not consistent, with relatively large numbers of smothering events occurring in specific locations for some sheds but not others. To the best of our knowledge, this study is the largest prospective study of smothering mortality in commercial free-range layer flocks conducted to date. Estimates of smothering incidence rate and how that varies within and between flocks and organisations over time provides a critically important benchmark for further investigations into this substantial area of productivity loss.
自 21 世纪初以来，发达国家的散养鸡蛋生产实践有所增加，部分原因是消费者认为散养住房更有利于母鸡福利。虽然与笼养系统中的家禽相比，散养系统中的家禽有更多的行为机会，但散养系统与更高频率的传染病、捕食和“窒息”有关，这种情况是指鸟类相互堆叠，导致窒息死亡。虽然澳大利亚散养层禽窒息死亡的频率在传闻中很高，但缺乏量化窒息导致特定死亡率的经验证据，也无法确定使鸟类面临更高窒息死亡风险的因素。这是一项对澳大利亚东部三个商业散养层组织管理的家禽群体进行的前瞻性队列研究。从 2019 年 1 月 1 日至 2021 年 3 月 29 日，将鸡群纳入研究，直到产蛋结束或 2022 年 3 月 31 日研究结束，以先发生者为准。在整个随访期间，鸡群经理使用定制的日志本提供每个鸡群的生产细节和窒息事件的细节。共有 84 个鸡群参加了这项研究：1 个来自组织 1，35 个来自组织 2，17 个来自组织 3。每个鸡群的鸟类数量从 16,000 到 45,000 只不等。总死亡率为每 10,000 只鸟年 1131 只死亡。三个组织的窒息死亡率为每 10,000 只鸟年风险 183 只（最低 133 只，最高 223 只）死亡。窒息约占所有死亡的 16%（最低 9%，最高 22%）。我们没有发现每日窒息风险与放置天数或日历日期之间存在明显的时间模式。棚内和户外区域窒息事件的位置不一致，对于一些棚舍，相对大量的窒息事件发生在特定位置，但对于其他棚舍则没有。据我们所知，这是迄今为止对商业散养层鸡群窒息死亡率进行的最大规模的前瞻性研究。估计窒息发生率以及随着时间的推移在鸡群和组织内和之间的变化，为进一步调查这一重要生产力损失领域提供了至关重要的基准。
