Drwencke Alycia M, Adcock Sarah J J, Walker Jenifer B, Tucker Cassandra B
Center for Animal Welfare, Department of Animal Science, University of California, Davis, Davis, CA 95616.
Animal Behavior Graduate Group, University of California, Davis, Davis, CA 95616.
JDS Commun. 2024 Feb 1;5(4):327-331. doi: 10.3168/jdsc.2023-0422. eCollection 2024 Jul.
Disbudding prevents horn growth in calves through thermal or chemical cauterization and causes damage that is painful for weeks following the procedure. Current pain management strategies are only effective from 1 to 2 h (local anesthetic) to 1 to 3 d (nonsteroidal anti-inflammatory drugs). A potential practical solution for addressing longer-term pain may be to administer ethanol as a cornual nerve block. When administered at a high concentration, ethanol damages the functionality of peripheral nerves, promoting localized long-lasting analgesia. It is also thought to be painful, thus ethanol may be combined with lidocaine, as a mixed solution or administered beforehand. We tested the use of an ethanol cornual nerve block for anesthesia around the horn bud in 2 pilot studies. We used different concentrations and amounts of ethanol (100% and 70%) in combination with different ratios of lidocaine in our attempt to identify an effective block. In pilot 1, 14 nondisbudded calves were administered 2 to 4 mL of 100% ethanol below the bony ridge on each side of the head to block the cornual nerve at 3 to 10 d of age (n = 28 horn buds) and observed for 5 wk. The duration of loss of sensation was evaluated using pinprick tests 10 min, 1, 3, and 7 d after the block, and then weekly thereafter until 35 d or full sensation had returned. Pinprick tests consisted of lightly pressing a needle in 10 evenly spaced locations around the base of the horn bud (0 responses = no sensation, 1-5 responses = partial sensation, 6-10 responses = full sensation). Pilot 2 looked at the 24 h after the injection and consisted of 9 nondisbudded calves (5 mL of 2:1, 70% ethanol and 2% lidocaine per horn bud) and 6 disbudded individuals (5 mL of 100% ethanol, 70% ethanol, or 2% lidocaine per horn bud). All treatments were administered at the calf level. Anesthesia was checked 10 min after the injection and 4 or 16 h later. In pilot 1, on the day of the ethanol injection (0 d), there was no sensation in 85% of horn buds. Sensation began to return as early as 1 d after blocking, with only 50%, 21%, and 3% of horn buds having no sensation at 1, 7, and 35 d, respectively. Partial sensation was present in 25%, 17%, and 10% of horn buds at these time points. In pilot 2, 27.8% of horn buds in the nondisbudded group had no sensation, whereas 33.3% had partial sensation 10 min after the injection. In the disbudded calves 10 min after the injection, 100% of horn buds from the 100% ethanol group had partial sensation and 100% of horn buds administered 70% ethanol had full sensation. Four or sixteen hours later, 100% of horn buds had full sensation. Together, in these pilot studies, ethanol provided inconsistent anesthesia when used for a cornual nerve block.
去角术通过热灼或化学烧灼防止犊牛角生长，会造成损伤，术后数周都会引起疼痛。目前的疼痛管理策略仅在1至2小时（局部麻醉剂）至1至3天（非甾体抗炎药）内有效。解决长期疼痛的一个潜在实用方案可能是将乙醇作为角神经阻滞剂使用。高浓度使用时，乙醇会损害外周神经的功能，促进局部持久镇痛。人们还认为其会引起疼痛，因此乙醇可与利多卡因混合使用，或以混合溶液形式使用或预先给药。我们在两项试点研究中测试了使用乙醇角神经阻滞对角芽周围进行麻醉。我们使用了不同浓度和量的乙醇（100%和70%），并结合不同比例的利多卡因，试图确定一种有效的阻滞方法。在试点1中，14头未去角的犊牛在3至10日龄时，在头部两侧的骨嵴下方注射2至4毫升100%乙醇以阻滞角神经（n = 28个角芽），并观察5周。在阻滞10分钟、1天、3天和7天后，然后此后每周进行针刺测试，评估感觉丧失的持续时间，直到35天或完全恢复感觉。针刺测试包括在角芽基部周围10个均匀间隔的位置轻轻按压一根针（0反应 = 无感觉，1 - 5反应 = 部分感觉，6 - 10反应 = 完全感觉）。试点2观察了注射后24小时的情况，包括9头未去角的犊牛（每个角芽注射5毫升2:1的70%乙醇和2%利多卡因）和6头去角的个体（每个角芽注射5毫升100%乙醇、70%乙醇或2%利多卡因）。所有处理均在犊牛水平进行。注射后10分钟以及4或16小时后检查麻醉情况。在试点1中，乙醇注射当天（0天），85%的角芽没有感觉。感觉最早在阻滞后1天开始恢复，在1天、7天和35天时，分别只有50%、21%和3%的角芽没有感觉。在这些时间点，25%、17%和10%的角芽有部分感觉。在试点2中，未去角组27.8%的角芽没有感觉，而注射后10分钟有33.3%的角芽有部分感觉。在去角的犊牛中，注射后10分钟，100%乙醇组的100%角芽有部分感觉，注射70%乙醇的100%角芽有完全感觉。4或16小时后，100%的角芽有完全感觉。总之，在这些试点研究中，乙醇用于角神经阻滞时提供的麻醉效果不一致。
