Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS 66506-0201, USA.
J Anim Sci. 2013 Sep;91(9):4426-39. doi: 10.2527/jas.2011-4411. Epub 2013 Jul 12.
Two experiments (384 pigs; C22 × L326; PIC) were conducted to determine the interactive effect of dietary L-carnitine and ractopamine HCl (RAC) on the metabolic response of pigs to handling. Experiments were arranged as split-split plots with handling as the main plot and diets as subplots (4 pens per treatment). Dietary L-carnitine (0 or 50 mg/kg) was fed from 36.0 kg to the end of the experiments (118 kg), and RAC (0 or 20 mg/kg) was fed the last 4 wk of each experiment. At the end of each experiment, 4 pigs per pen were assigned to 1 of 2 handling treatments. Gently handled pigs were moved at a moderate walking pace 3 times through a 50-m course and up and down a 15° loading ramp. Aggressively handled pigs were moved as fast as possible 3 times through the same course, but up and down a 30° ramp, and shocked 3 times with an electrical prod. Blood was collected immediately before and after handling in Exp. 1 and immediately after and 1 h after handling in Exp. 2. Feeding RAC increased (P < 0.01) ADG and G:F, but there was no effect (P > 0.10) of L-carnitine on growth performance. In Exp. 1 and 2, aggressive handling increased (P < 0.01) blood lactate dehydrogenase (LDH), lactate, cortisol, and rectal temperature and decreased blood pH. In Exp. 1, there was a RAC × handling interaction (P < 0.06) for the difference in pre- and posthandling blood pH and rectal temperature. Aggressively handled pigs fed RAC had decreased blood pH and increased rectal temperature compared with gently handled pigs, demonstrating the validity of the handling model. Pigs fed RAC had increased (P < 0.01) LDH compared with pigs not fed RAC. Pigs fed L-carnitine had increased (P < 0.03) lactate compared with pigs not fed L-carnitine. In Exp. 2, pigs fed RAC had lower (P < 0.02) blood pH immediately after handling, but pH returned to control levels by 1 h posthandling. Lactate, LDH, cortisol, and rectal temperature changes from immediately posthandling to 1 h posthandling were not different (P > 0.10) between pigs fed L-carnitine and those fed RAC, indicating that L-carnitine did not decrease recovery time of pigs subjected to aggressive handling. These results suggest that pigs fed 20 mg/kg of RAC are more susceptible to stress when handled aggressively compared with pigs not fed RAC. Dietary L-carnitine fed in combination with RAC did not alleviate the effects of stress. This research emphasizes the importance of using proper animal handling techniques when marketing finishing pigs fed RAC.
两个试验（384 头猪；C22×L326；PIC）旨在确定日粮 L-肉碱和盐酸莱克多巴胺（RAC）对猪处理代谢反应的交互作用。试验采用裂区设计，处理为副区（每处理 4 个栏），处理为主区（处理为 4 个区组）。从 36.0kg 到试验结束（118kg），猪日粮添加或不添加 50mg/kg 的 L-肉碱，试验最后 4 周，猪日粮添加或不添加 20mg/kg 的 RAC。每个试验结束时，每个栏 4 头猪随机分配到 2 种处理之一。温和处理的猪在 50m 课程中以中等步行速度移动 3 次，上下 15°的装载斜坡。剧烈处理的猪以最快速度通过相同的课程移动 3 次，但上下 30°的斜坡，并用电棒电击 3 次。在试验 1 中，在处理前和处理后立即采集血液，在试验 2 中，在处理后立即和处理后 1h 采集血液。在试验 1 和 2 中，剧烈处理增加（P＜0.01）了乳酸脱氢酶（LDH）、乳酸、皮质醇和直肠温度，并降低了血液 pH 值。在试验 1 中，存在 RAC×处理的交互作用（P＜0.06），即处理前后血液 pH 值和直肠温度的差异。与温和处理的猪相比，饲喂 RAC 的剧烈处理猪的血液 pH 值降低，直肠温度升高，表明处理模型有效。与未饲喂 RAC 的猪相比，饲喂 RAC 的猪 LDH 增加（P＜0.01）。与未饲喂 L-肉碱的猪相比，饲喂 L-肉碱的猪的乳酸（P＜0.03）增加。在试验 2 中，饲喂 RAC 的猪在处理后立即的血液 pH 值较低（P＜0.02），但在处理后 1h 时 pH 值恢复到对照水平。饲喂 L-肉碱和未饲喂 RAC 的猪在处理后立即到 1h 之间的乳酸、LDH、皮质醇和直肠温度的变化没有差异（P＞0.10），表明 L-肉碱没有减少遭受剧烈处理的猪的恢复时间。这些结果表明，与未饲喂 RAC 的猪相比，饲喂 20mg/kg RAC 的猪在受到剧烈处理时更容易受到应激。日粮中添加 L-肉碱与 RAC 结合使用并不能减轻应激的影响。本研究强调了在销售饲喂 RAC 的育肥猪时使用适当的动物处理技术的重要性。
