Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
J Anim Sci. 2011 Oct;89(10):3318-25. doi: 10.2527/jas.2011-4104. Epub 2011 May 27.
Surgical castration is performed on most male piglets in the United States. However, castration is painful and analgesics have been considered to relieve pain. Inhalant gases with analgesic properties allow for a fast induction, have short-term and reversible effects, and are a needle-free option. Nitrous oxide (N(2)O; "laughing gas") has been widely used in human surgery and dental offices as an analgesic, sedative, and anxiolytic drug, yet N(2)O has not been thoroughly investigated for use in farm animals. We hypothesized that the analgesic effect of N(2)O could reduce the pain experienced by piglets during or immediately after castration. Twenty-four male piglets, from 12 litters, were castrated at 3 d of age. One piglet received N(2)O and a littermate received air as a control. After 150 s of exposure to the gas, castration was performed while the piglet remained exposed to the gas. Agitation scores and total vocalization length were recorded during castration. Behavioral observations were continued for 3 d postcastration by using a 5-min scan-sampling method for 4 h the first morning and for 2-h periods in the morning and afternoon of each day thereafter. Body weight gain was measured on the day before castration, at 3 d postcastration, and at weaning. Data were analyzed using a mixed model in SAS (Cary, NC). Nitrous oxide successfully induced anesthesia in all N(2)O piglets, as validated by a skin pinch test and the loss of the palpebral reflex. Total vocalization length was shorter in piglets receiving N(2)O during the induction phase (P = 0.003) but was not different during castration itself because piglets receiving N(2)O awoke and vocalized as much as control piglets (P = 0.87). Agitation scores during the whole procedure were reduced in piglets receiving N(2)O in both frequency (P = 0.005) and intensity (P = 0.026). For 2 h after castration, piglets receiving N(2)O displayed less huddling behavior than did control piglets (P = 0.01). Over the 3 d, piglets receiving N(2)O performed more tail wagging (P = 0.02) and tended to show fewer sleep spasms (P = 0.06) than did control piglets. Piglets given N(2)O tended to have a reduced growth rate compared with control piglets at 3 d postcastration and at weaning (P = 0.05 and P = 0.06, respectively). Nitrous oxide was effective in inducing anesthesia in neonatal piglets during handling. Nonetheless, its analgesic effects appeared insufficient in preventing castration-induced pain.
在美国，大多数公猪崽在接受外科阉割。然而，阉割是痛苦的，因此人们考虑使用镇痛剂来缓解疼痛。具有镇痛作用的吸入性气体可以快速诱导麻醉，具有短期和可逆的作用，并且是一种无针选择。一氧化二氮（N2O；“笑气”）已在人类手术和牙科诊所中广泛用作镇痛药、镇静剂和抗焦虑药，但尚未对其在农场动物中的应用进行彻底研究。我们假设 N2O 的镇痛作用可以减轻阉割过程中或之后公猪崽的疼痛。24 只公猪崽，来自 12 窝，在 3 日龄时接受阉割。一只猪崽接受 N2O，而一只同窝猪崽接受空气作为对照。在暴露于气体 150 秒后，在猪崽仍暴露于气体的情况下进行阉割。在阉割过程中记录躁动评分和总发声长度。阉割后第 3 天，通过使用 5 分钟扫描采样法，在前一天早上进行 4 小时，此后每天早上和下午进行 2 小时的观察，继续进行 3 天的行为观察。在阉割前一天、阉割后第 3 天和断奶时测量体重增加。数据使用 SAS（卡里，NC）中的混合模型进行分析。一氧化二氮成功地诱导了所有 N2O 猪崽的麻醉，这通过皮肤捏测试和瞬目反射的丧失得到了验证。在诱导阶段，接受 N2O 的猪崽的总发声长度更短（P=0.003），但在阉割本身期间没有差异，因为接受 N2O 的猪崽醒来并像对照猪崽一样发声（P=0.87）。在整个过程中，接受 N2O 的猪崽的躁动评分在频率（P=0.005）和强度（P=0.026）上均降低。在阉割后 2 小时内，接受 N2O 的猪崽比对照组猪崽的蜷缩行为更少（P=0.01）。在 3 天内，接受 N2O 的猪崽的尾巴摆动更多（P=0.02），并且睡眠痉挛的次数更少（P=0.06），而对照组的猪崽则较少。与对照组相比，接受 N2O 的猪崽在阉割后第 3 天和断奶时的生长速度较慢（P=0.05 和 P=0.06）。一氧化二氮在处理新生仔猪时有效地诱导麻醉。然而，它的镇痛作用似乎不足以预防阉割引起的疼痛。
