School of Agriculture & Environment, The University of Western Australia, 35 Stirling Highway, Perth 6009, Western Australia, Australia.
School of Human Sciences, The University of Western Australia, 35 Stirling Highway, Perth 6009, Western Australia, Australia.
Animal. 2021 Jan;15(1):100067. doi: 10.1016/j.animal.2020.100067. Epub 2020 Dec 10.
The origins of floor-laying in ducks could be low motivation for a nest, or stress related to difficulties with accessing a nest (e.g. competition). Using a behavioural demand test, we investigated if increasing the work required to access their nest impacted ducks' behaviour and two indicators of stress: egg corticosterone concentration and elevation of core body temperature (stress-induced hyperthermia (SIH)). Twelve laying Pekin ducks previously trained in an operant push-door task were required to use a push-door to access their nest. The door was loaded with increasing weight (0-160% of individual BW, four nights per workload) and eventually blocked to prevent nest access. Before testing, temperature data loggers were implanted in the abdomen. Eggs were collected daily to measure corticosterone concentrations. Behaviour towards the push-door was quantified. Three birds were excluded from the experiment at an early stage. Five of the nine remaining birds pushed all workloads up to 160% BW and attempted to pass the blocked door, with another two birds pushing up to 80 and 140% BW. For those that pushed at all workloads (n = 5) the area under the curve (AUC) of hyperthermia was larger at workloads of 80% (P < 0.001), 120% (P < 0.01), 140% (P < 0.001), 160% (P < 0.001), and when the door was blocked (P < 0.001), compared with 0%. On the first night when the door was blocked, all five birds pushed more at the door, but no attempts were made to push on the following 3 nights, yet the AUC of hyperthermia did not differ between nights 2-4 of the blocked door, compared with the first night that the door was blocked. Increasing workload and inability to access the nest had no effect on corticosterone in egg albumen. It was concluded that laying Pekin ducks were motivated to access a nest. Although it was not possible to differentiate metabolic from psychogenic stress on the first night that nest access was denied, we suggest that the occurrence of hyperthermia on the subsequent nights was due to SIH resulting from frustration at their inability to use their preferred nest. Floor-laying therefore is unlikely due solely to low nest-seeking motivation. Egg corticosterone was not a relevant indicator of acute stress. Strategies to improve nest availability (e.g. decreasing competition) could improve the welfare of commercial ducks.
鸭铺巢行为的起源可能是对巢的低动机，或者是由于难以进入巢而产生的压力（例如竞争）。我们使用行为需求测试来研究增加进入巢的工作难度是否会影响鸭子的行为和两个压力指标：卵皮质酮浓度和核心体温升高（应激性高热（SIH））。 12 只之前在操作性推门任务中受过训练的产蛋北京鸭需要使用推门将其巢进入。门被加载了越来越重的重量（0-160％的个体 BW，四个晚上的每个工作量），最终被阻塞以防止进入巢穴。在测试之前，腹部植入了温度数据记录器。每天收集鸡蛋以测量皮质酮浓度。对推门的行为进行了量化。三只鸟在早期阶段被排除在实验之外。其余九只中的五只将所有工作量推至 160％BW 并试图通过被阻塞的门，另外两只将工作量推至 80％和 140％BW。对于那些在所有工作量下推的鸟（n=5），在工作量为 80％（P<0.001），120％（P<0.01），140％（P<0.001），160％（P<0.001）和门被阻塞时（P<0.001），与 0％相比，高热的 AUC 更大。在门被阻塞的第一晚，所有五只鸟都在门上推得更多，但在接下来的 3 晚都没有尝试推，然而，与门被阻塞的第一晚相比，在门被阻塞的第二至第四晚，高热的 AUC 没有差异。增加工作量和无法进入巢穴对卵白蛋白中的皮质酮没有影响。研究结论表明，产蛋北京鸭有进入巢穴的动机。尽管在首次拒绝进入巢穴的当晚无法区分代谢性与精神性应激，但我们认为，在随后的几晚出现高热可能是由于无法使用首选巢穴而导致的挫折导致的 SIH。因此，铺巢行为不太可能仅仅是由于对巢穴的低动机所致。卵皮质酮不是急性应激的相关指标。改善巢穴可用性（例如减少竞争）的策略可以改善商业鸭的福利。
