Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas 66506, USA.
J Dairy Sci. 2013 Aug;96(8):5194-205. doi: 10.3168/jds.2012-6251. Epub 2013 Jun 5.
Dehorning is a painful husbandry procedure that is commonly performed in dairy calves. Parenteral meloxicam combined with local anesthesia mitigates the physiological and behavioral effects of dehorning in calves. The purpose of this study was to determine the influence of timing of oral meloxicam administration on physiological responses in calves after dehorning. Thirty Holstein bull calves, 8 to 10 wk of age (28-70 kg), were randomly assigned to 1 of 3 treatment groups: placebo-treated control group (n=10), calves receiving meloxicam administered orally (1 mg/kg) in powdered milk replacer 12h before cautery dehorning (MEL-PRE; n=10), and calves receiving meloxicam administered as an oral bolus (1 mg/kg) at the time of dehorning (MEL-POST; n=10). Following cautery dehorning, blood samples were collected to measure cortisol, substance P (SP), haptoglobin, ex vivo prostaglandin E2 (PgE2) production after lipopolysaccharide stimulation and meloxicam concentrations. Maximum ocular temperature and mechanical nociceptive threshold (MNT) were also assessed. Data were analyzed using noncompartmental pharmacokinetic analysis and repeated measures ANOVA models. Mean peak meloxicam concentrations were 3.61±0 0.21 and 3.27±0.14 μg/mL with average elimination half-lives of 38.62±5.87 and 35.81±6.26 h for MEL-PRE and MEL-POST, respectively. Serum cortisol concentrations were lower in meloxicam-treated calves compared with control calves at 4 h postdehorning. Substance P concentrations were significantly higher in control calves compared with meloxicam-treated calves at 120 h after dehorning. Prostaglandin E2 concentrations were lower in meloxicam-treated calves compared with control calves. Mechanical nociceptive threshold was higher in control calves at 1h after dehorning, but meloxicam-treated calves tended to have a higher MNT at 6h after dehorning. No effect of timing of meloxicam administration on serum cortisol concentrations, SP concentrations, haptoglobin concentrations, maximum ocular temperature, or MNT was observed. However, PgE2 concentrations in MEL-PRE calves were similar to control calves after 12h postdehorning, whereas MEL-POST calves had lower PgE2 concentrations for 3 d postdehorning. These findings support that meloxicam reduced cortisol, SP, and PgE2 after dehorning, but only PgE2 production was significantly affected by the timing of meloxicam administration.
去角是一种常见的奶牛场小牛的疼痛性饲养程序。注射用美洛昔康联合局部麻醉可减轻小牛去角的生理和行为影响。本研究的目的是确定口服美洛昔康给药时间对去角后小牛生理反应的影响。30 头荷斯坦公牛犊，8-10 周龄（28-70kg），随机分为 3 个治疗组之一：安慰剂对照组（n=10）、术前 12 小时口服美洛昔康（1mg/kg）混悬于牛奶代用品中（MEL-PRE；n=10）和去角时口服美洛昔康（1mg/kg）（MEL-POST；n=10）。去角后，采集血样测量皮质醇、P 物质（SP）、触珠蛋白、脂多糖刺激后体外前列腺素 E2（PgE2）产生和美洛昔康浓度。还评估了最大眼温和机械痛觉阈值（MNT）。使用非房室药代动力学分析和重复测量方差分析模型分析数据。MEL-PRE 和 MEL-POST 的平均峰美洛昔康浓度分别为 3.61±0.02μg/ml 和 3.27±0.14μg/ml，平均消除半衰期分别为 38.62±5.87h 和 35.81±6.26h。去角后 4h，美洛昔康治疗组小牛血清皮质醇浓度低于对照组小牛。去角后 120h，对照组小牛的 P 物质浓度明显高于美洛昔康治疗组小牛。美洛昔康治疗组小牛的前列腺素 E2 浓度低于对照组小牛。去角后 1h，对照组小牛的机械痛觉阈值较高，但去角后 6h，美洛昔康治疗组小牛的 MNT 倾向较高。美洛昔康给药时间对血清皮质醇浓度、SP 浓度、触珠蛋白浓度、最大眼温或 MNT 无影响。然而，MEL-PRE 组小牛去角后 12h 的 PgE2 浓度与对照组相似，而 MEL-POST 组小牛去角后 3d 的 PgE2 浓度较低。这些发现支持美洛昔康在去角后降低皮质醇、SP 和 PgE2，但只有 PgE2 的产生受到美洛昔康给药时间的显著影响。
