Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
J Anim Sci. 2013 Apr;91(4):1874-83. doi: 10.2527/jas.2012-5761. Epub 2013 Jan 23.
The search for alternative methods to euthanize piglets is critical to address public concern that current methods are not optimal. Scientific evidence supports that blunt force trauma is humane when performed correctly, but most people find it visually difficult to accept. The use of CO2 is often recommended; at the same time, it is criticized as being aversive to pigs. This research sought to 1) identify a method of scientifically determining if piglets find a gas aversive, using an approach-avoidance test, which relies on the perspective of the piglet, and 2) test different gas mixtures to determine if they are effective and humane for neonatal piglet euthanasia. Pigs were allowed to walk freely between 1 chamber filled with air and another chamber either gradually filled with gas mixtures (Exp. 1) or prefilled with gas mixtures (Exp. 2). Experiment 1 tested CO2 (90%) and air (10%), N2O (60%) and CO2 (30%), Ar (60%) and CO2 (30%), and N2 (60%) and CO2 (30%). Because piglets had to be removed when they started to flail, the test was shortest (P < 0.01) for the pigs in the CO2 treatment compared with pigs in the N2O/CO2, Ar/CO2, and N2/CO2 treatments, 3.1 ± 0.2, 8.5 ± 0.6, 9.6 ± 0.4, and 9.9 ± 0.1 min, respectively. Nonetheless, all gas mixtures adversely affected the pigs, causing the pigs to leave the test chamber. In Exp. 2, piglets were allowed to enter a chamber prefilled with N2/CO2 or N2O/CO2 (both 60/30%). Pigs exposed to the prefill chambers started to flail in fewer than 20 s, much faster in comparison with the gradual fill method, which supports that this method was more aversive. In Exp. 3, piglets were euthanized using a 2-step procedure. Pigs were first placed in a gradual fill chamber with 1 of 4 gas mixtures: 90% CO2, N2/CO2, N2O/CO2, or N2O/O2 (the last 3 mixtures at 60/30%) followed by placement into a 90% CO2 prefill chamber when the pigs started to flail or were anesthetized. All 3 gas treatments that contained CO2 killed pigs more quickly than N2O/O2 (P < 0.05). However, N2O/O2 was the only treatment that anesthetized the pigs instead of causing squeals or flailing although requiring about 12 min longer. Although longer, a 2-step procedure in which pigs are anesthetized with a mixture of N2O and O2 before being euthanized by immersion in CO2 may prove to be more humane than CO2 alone.
寻找替代方法来使仔猪安乐死对于解决公众关注的当前方法不理想的问题至关重要。科学证据表明，当正确实施时，钝力创伤是人道的，但大多数人发现从视觉上很难接受。二氧化碳的使用通常是推荐的；同时，它被批评为对猪有厌恶感。本研究旨在 1）确定一种科学方法来确定仔猪是否发现气体有厌恶感，使用回避-接近测试，该测试依赖于仔猪的视角，以及 2）测试不同的气体混合物，以确定它们是否对新生仔猪安乐死有效和人道。猪被允许在充满空气的一个室和另一个逐渐充满气体混合物的室（实验 1）或预充满气体混合物的室（实验 2）之间自由行走。实验 1 测试了二氧化碳（90%）和空气（10%）、一氧化二氮（60%）和二氧化碳（30%）、氩气（60%）和二氧化碳（30%）以及氮气（60%）和二氧化碳（30%）。因为当仔猪开始抽搐时必须将它们移走，所以与一氧化二氮/二氧化碳、氩气/二氧化碳和氮气/二氧化碳处理的仔猪相比，二氧化碳处理的仔猪的测试时间最短（P <0.01），分别为 3.1 ± 0.2、8.5 ± 0.6、9.6 ± 0.4 和 9.9 ± 0.1 分钟。尽管如此，所有的气体混合物都对仔猪产生了不利影响，导致仔猪离开测试室。在实验 2 中，仔猪被允许进入预先充满氮气/二氧化碳或一氧化二氮/二氧化碳的室（均为 60/30%）。暴露于预填充室的仔猪在不到 20 秒内开始抽搐，与逐渐填充方法相比快得多，这表明这种方法更具厌恶感。在实验 3 中，仔猪使用两步程序进行安乐死。仔猪首先被放置在一个逐渐充满气体混合物的室中，有 4 种气体混合物可供选择：90%的二氧化碳、氮气/二氧化碳、一氧化二氮/二氧化碳或一氧化二氮/氧气（最后 3 种混合物为 60/30%），然后当仔猪开始抽搐或麻醉时，将其放入 90%的二氧化碳预填充室中。所有包含二氧化碳的 3 种气体处理方法都比一氧化二氮/氧气更快地杀死仔猪（P <0.05）。然而，一氧化二氮/氧气是唯一一种使仔猪麻醉而不是引起尖叫或抽搐的治疗方法，尽管需要大约 12 分钟的时间。尽管时间较长，但在将仔猪麻醉混合有一氧化二氮和氧气后，再将其浸入二氧化碳中进行安乐死的两步程序可能比单独使用二氧化碳更人道。
