Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3, Canada.
Public Health Risk Sciences Division, Public Health Agency of Canada, 160 Research Lane, Guelph, Ontario N1G 5B2, Canada.
J Dairy Sci. 2017 Dec;100(12):9667-9673. doi: 10.3168/jds.2017-13196. Epub 2017 Oct 4.
Waste milk feeding is a common practice in dairy operations. Regardless of the benefits of this practice to the dairy farmers, concerns from the potential dissemination of antimicrobial-resistant bacteria through the gut and subsequent shedding by calves into the environment are increasing. In this study, we employed Monte Carlo simulation to assess the risk of shedding extended-spectrum cephalosporin-resistant Escherichia coli (ESC-R E. coli) caused by waste milk feeding in pre-weaned calves using an exponential dose-response model fit to data for E. coli O157:H7 in cattle. Data from pertinent studies were included in our model to predict the risk of shedding. The median (5th and 95th percentiles) for the daily risk of shedding ESC-R E. coli by calves fed only contaminated waste milk was predicted to be 2.9 × 10 (2.1 × 10, 3.7 × 10), representing a median daily risk of 29 out of 10,000 calves shedding ESC-R E. coli due to exclusive feeding of waste milk containing ESC-R E. coli. This median value was reduced by 94% when accounting for the proportion of waste milk that does not contain ESC-R E. coli. The overall risk of shedding ESC-R E. coli through the pre-weaning period for farms that feed waste milk to calves was 5.7 × 10 (2.4 × 10, 1.1 × 10), representing 57 out of 10,000 calves. When accounting for the proportion of farms that do not feed waste milk, the pre-weaning period risk was reduced by 23%. By varying the prevalence of ESC-R E. coli in waste milk using values of 3, 1.5, and 1%, the daily risk of shedding decreased by factors of 50, 65, and 82%, respectively, which supports the reduction of contamination or discontinuation of feeding waste milk containing ESC-R E. coli as major mitigation measures to reduce the risk of shedding caused by ingestion of resistant bacteria. It is anticipated that the effects of antimicrobial residues in waste milk, which was not considered herein due to lack of data, would further increase risks. Although waste milk feeding to calves may be economically beneficial to the dairy farmers, there exists the risk of dissemination of ESC-resistant bacteria into the environment.
废弃牛奶喂养在奶牛场中是一种常见做法。尽管这种做法对奶农有好处，但人们越来越担心通过肠道传播和随后牛犊排泄到环境中的抗生素耐药菌的潜在传播。在这项研究中，我们采用蒙特卡罗模拟方法，使用牛源大肠杆菌 O157:H7 的指数剂量反应模型来评估因废奶喂养而导致未断奶牛犊排泄超广谱头孢菌素耐药大肠杆菌（ESC-R E. coli）的风险。我们的模型纳入了相关研究的数据，以预测排泄风险。仅用受污染的废奶喂养的牛犊每天排泄 ESC-R E. coli 的风险中位数（第 5 个和第 95 个百分位数）预计为 2.9×10（2.1×10，3.7×10），表示由于仅用含有 ESC-R E. coli 的废奶喂养，每 10000 头牛犊中有 29 头牛犊每天排泄 ESC-R E. coli。当考虑到不含 ESC-R E. coli 的废奶比例时，该中位数值降低了 94%。在给牛犊喂废奶的农场中，通过在哺乳期期间排泄 ESC-R E. coli 的总体风险为 5.7×10（2.4×10，1.1×10），表示每 10000 头牛犊中有 57 头。当考虑到不喂废奶的农场比例时，哺乳期期间的风险降低了 23%。通过使用 3%、1.5%和 1%的废奶中 ESC-R E. coli 的流行率来改变值，每天排泄的风险分别降低了 50%、65%和 82%，这支持减少污染或停止喂养含有 ESC-R E. coli 的废奶，作为减少因摄入耐药菌而导致排泄的主要缓解措施。预计由于缺乏数据，废奶中的抗菌药物残留的影响会进一步增加风险。尽管废弃牛奶喂养犊牛对奶农可能具有经济上的好处，但存在将 ESC 耐药菌传播到环境中的风险。
