Edrington T S, Callaway T R, Ives S E, Engler M J, Welsh T H, Hallford D M, Genovese K J, Anderson R C, Nisbet D J
Food and Feed Safety Research Unit, ARS-USDA, 2881, F&B Road, College Station, TX 77845, USA.
Curr Microbiol. 2006 Oct;53(4):340-5. doi: 10.1007/s00284-006-0200-9. Epub 2006 Sep 12.
The effects of the beta-agonist ractopamine, recently approved for use in feedlot cattle to improve carcass quality and performance, on fecal shedding Escherichia coli O157:H7 and Salmonella in feedlot cattle was examined. In the first study, 20 feedlot steers and heifers were randomly assigned to receive ractopamine or no ractopamine (control) by way of oral bolus for 28 days. Fecal samples were collected daily, and shedding of E. coli O157:H7 determined. When examined during the entire 28-day experimental period, ractopamine decreased (P = 0.0006) the percentage of cattle shedding E. coli O157:H7 (58% vs. 42% for control and ractopamine treatments, respectively). A second study was conducted in a commercial feedlot facility in the southwestern United States. Eighteen pens of cross-bred beef heifers (approximately 100 head/pen and 9 pens/treatment) were randomly assigned to receive either 0 (control) or 200 mg ractopamine/head x d(-1). Fresh fecal samples (30/pen) were collected off the pen floor before ractopamine supplementation and again after approximately 28 days of ractopamine supplementation (within a few days of slaughter); the samples were cultured for E. coli O157:H7 and Salmonella. The percentage of animals shedding E. coli O157:H7 was decreased when data were pooled across replicates (P = 0.05) in ractopamine-treated cattle compared with controls. The percentage of animals shedding Salmonella tended to be higher (P = 0.08) with the ractopamine treatment when data were pooled across replicates. Although further research is required to confirm these results, the potential food safety implications of this research are intriguing.
最近被批准用于饲养场牛以改善胴体品质和性能的β-激动剂莱克多巴胺，对饲养场牛粪便中大肠杆菌O157:H7和沙门氏菌排泄的影响进行了研究。在第一项研究中，20头饲养场阉牛和小母牛通过口服大丸剂随机分配接受莱克多巴胺或不接受莱克多巴胺（对照），持续28天。每天收集粪便样本，并测定大肠杆菌O157:H7的排泄情况。在整个28天的实验期内进行检查时，莱克多巴胺降低了（P = 0.0006）排泄大肠杆菌O157:H7的牛的百分比（对照和莱克多巴胺处理组分别为58%和42%）。第二项研究在美国西南部的一个商业饲养场设施中进行。18栏杂交肉牛小母牛（每栏约100头，每种处理9栏）被随机分配接受0（对照）或200毫克莱克多巴胺/头×天⁻¹。在补充莱克多巴胺前从栏舍地面采集新鲜粪便样本（每栏30份），在补充莱克多巴胺约28天后（屠宰前几天内）再次采集；样本进行大肠杆菌O157:H7和沙门氏菌培养。与对照组相比，莱克多巴胺处理的牛在重复样本合并数据时，排泄大肠杆菌O157:H7的动物百分比降低（P = 0.05）。在重复样本合并数据时，莱克多巴胺处理的动物排泄沙门氏菌的百分比倾向于更高（P = 0.08）。尽管需要进一步研究来证实这些结果，但这项研究潜在的食品安全影响很有趣。
