Center for Proper Housing: Poultry and Rabbits, Animal Welfare Division, Vetsuisse-Faculty, University of Bern, Burgerweg 22, 3052 Zollikofen, Switzerland.
Center for Proper Housing: Poultry and Rabbits, Animal Welfare Division, Vetsuisse-Faculty, University of Bern, Burgerweg 22, 3052 Zollikofen, Switzerland.
Animal. 2022 Aug;16(8):100567. doi: 10.1016/j.animal.2022.100567. Epub 2022 Jul 15.
Piling behaviour of laying hens often results in smothering or death due to suffocation. Mechanisms leading to piling are not yet understood though various potential factors have been suggested. In this experimental study, we predicted that the presence of a light spot, a novel object (metal foil), or a heat area within animal pens would increase animal numbers around the stimulus leading to piling behaviour. We presented the cues in a 4 × 2 Latin-square design in eight identical experimental pens including each 55 Lohmann Selected Leghorn hens. The cues were presented in two test areas per pen, at two bouts per day in the morning, consecutively for 5 days, over four periods (age: 20, 22, 24, 26 weeks). Each pen received a cue and control condition simultaneously (test areas without cue presentation) once. For a bout, each cue was presented for 35 min except for the light spot where the duration was 10 min. Birds' responses to the cues during bout and non-bout times were video recorded and analysed for the first bout of each period. To assess the cues' attractiveness, the number of hens during bout times was counted at predefined times within the test and control areas. To assess the cues' effects on piling, we described piling behaviour (pile number, duration, animal numbers, trigger) in control and test areas during bout times. Furthermore, we described piling behaviour during bout times and non-bout times on the first day of the first period and fourth period. The best model explaining the number of hens included the interactions of treatment and bout time, and treatment and area. Over the bout's time course, more hens were attracted to the light spot compared to the control condition, and more to test areas compared to control areas. In the novel object condition, more hens were drawn to the test areas compared to the control areas. Hens were not attracted to the heat area. Piling in bout times was observed twice when hens pecked at the novel object. During non-bout times, piling behaviour occurred frequently at midday and in the late morning compared to the afternoon, mostly in corners and mainly preceded by the mutual attraction of hens. Overall, hens were attracted to light spots and less so to the novel object though neither reliably induced piling behaviour. The occurrence of piling behaviour in non-bout times shows that more work is needed to understand mechanisms eliciting piling behaviour.
产蛋鸡的堆叠行为常常导致窒息或死亡。尽管已经提出了各种潜在的因素，但导致堆叠的机制仍不清楚。在这项实验研究中，我们预测动物围栏内存在光点、新奇物体（金属箔）或热区会增加动物在刺激周围的数量，从而导致堆叠行为。我们在八个相同的实验围栏中以 4×2 拉丁方设计呈现线索，每个围栏包括 55 只洛曼精选来亨母鸡。在每天早上的两回合中，在每个围栏的两个测试区域中呈现线索，连续进行 5 天，共进行四个周期（年龄：20、22、24、26 周）。每个围栏同时接受一个线索和对照条件（测试区域没有呈现线索）一次。对于一回合，除了持续 10 分钟的光点外，每个线索的呈现时间均为 35 分钟。在回合和非回合时间，通过视频记录鸟类对线索的反应，并分析每个周期的第一个回合。为了评估线索的吸引力，在测试和对照区域内的预定时间内，计算回合时间内母鸡的数量。为了评估线索对堆叠的影响，我们在回合时间内描述控制和测试区域内的堆叠行为（堆叠数量、持续时间、动物数量、触发）。此外，我们还描述了第一个周期和第四个周期第一天的回合时间和非回合时间内的堆叠行为。解释母鸡数量的最佳模型包括处理和回合时间以及处理和区域之间的相互作用。在回合的时间过程中，与对照条件相比，更多的母鸡被光点吸引，与对照区域相比，更多的母鸡被测试区域吸引。在新奇物体条件下，与对照区域相比，更多的母鸡被测试区域吸引。母鸡对热区没有吸引力。当母鸡啄新奇物体时，在回合时间内观察到两次堆叠。在非回合时间内，与下午相比，中午和清晨时分经常发生堆叠行为，主要发生在角落，主要是母鸡相互吸引引起的。总体而言，母鸡被光点吸引，对新奇物体的吸引力较小，但两者都不能可靠地引起堆叠行为。非回合时间内堆叠行为的发生表明，需要做更多的工作来理解引发堆叠行为的机制。
