Antibiotic use on German pig farms - A longitudinal analysis for 2011, 2013 and 2014

To study antibiotic use in livestock in a temporal context with the development of antimicrobial resistance, long-term changes in antibiotic use must be mapped and their possible causes must be explored. Therefore, the present work assesses the changes in antibiotic use over time in German livestock husbandry. In addition, factors associated with antibiotic use were analyzed to identify possible strategies for further reducing antimicrobial usage. For 2011, 2013 and 2014, antibiotic usage data were collected and examined within the VetCAb project. Three hundred participating pig holdings provided information on their antibiotic use based on obligatory application and delivery forms (ADFs) filled in by their veterinarian as well as information on their current stabling capacities for each production type held. Data on sow, piglet, weaner and fattening pig holdings were described separately, using the semi-annual treatment frequency (TF) to measure antibiotic consumption. Multiple linear mixed models were used to investigate the effects of time, farm size, region and farm management category on the treatment frequency. The study yielded significant time changes with p-values below 0.001 in antibiotic administration with a decreasing median TF in piglets from 3.8 in the first half of 2011 (IQR = 1.1–10.6) to 1.7 in the second half of 2014 (IQR = 0.2–4.5) and in fattening pigs from 5.1 in the first half of 2011 (IQR = 0.2–15.4) to 0.7 in the second half of 2014 (IQR = 0.1–6.7). Meanwhile the TF fluctuated between 8.2 and 12.2 in weaners during the observational period (IQRs between zero (lower quartile) and 37.9 (upper quartile)). Piglet, weaner and fattening pig holdings belonging to the upper third of the holdings in size used significantly more antibiotics than the other holdings investigated. Particularly for weaner and fattening pig holdings, a higher TF was noted for farms without breeding units. The region was only a significant factor in weaners. In conclusion, for 2011, 2013 and 2014, the present study shows a clear reduction in antibiotic treatment frequency in German pig holdings. In addition, the association with various factors such as herd size and farm organization on the antibiotic usage frequency is indisputable. Therefore, these factors should be included in monitoring systems and considered when evaluating intervention measures.

为在抗菌药物耐药性（antimicrobial resistance）演化的时间维度下探究畜禽养殖中的抗生素使用情况，需绘制抗生素使用的长期变化图谱并剖析其潜在诱因。为此，本研究针对德国畜牧业的抗生素使用随时间的变化展开评估。此外，本研究还分析了与抗生素使用相关的影响因素，以期识别进一步降低抗菌药物使用量的可行策略。

在VetCAb项目框架下，研究人员收集并分析了2011、2013及2014年的抗生素使用数据。共有300家参与调研的养猪场提供了由其兽医填写的强制性用药与配送单据（application and delivery forms，ADFs），以及各生产类型对应的当前圈养产能信息。研究针对母猪场、仔猪场、断奶仔猪场及育肥猪场分别进行描述，采用半年度治疗频次（treatment frequency，TF）作为抗生素消耗量的衡量指标。

本研究采用多元线性混合模型（multiple linear mixed models），探究时间、猪场规模、区域及猪场管理类别对治疗频次的影响。研究结果显示，抗生素给药情况存在显著的时间变化（p值（p-value）小于0.001）：仔猪的治疗频次中位数从2011年上半年的3.8（四分位距（Interquartile Range，IQR）=1.1–10.6）降至2014年下半年的1.7（IQR=0.2–4.5）；育肥猪的治疗频次中位数则从2011年上半年的5.1（IQR=0.2–15.4）降至2014年下半年的0.7（IQR=0.1–6.7）。与此同时，观测期内断奶仔猪的治疗频次在8.2至12.2之间波动（IQR范围为0（下四分位数）至37.9（上四分位数））。猪场规模处于前三分之一梯队的仔猪场、断奶仔猪场及育肥猪场，其抗生素使用量显著高于其余受访猪场。尤其对于断奶仔猪场和育肥猪场，无育种单元的猪场治疗频次更高。区域因素仅对断奶仔猪场存在显著影响。

综上，针对2011、2013及2014年的调研结果显示，德国养猪场的抗生素治疗频次已出现显著下降。此外，猪场规模与猪场运营模式等因素与抗生素使用频次存在明确关联。因此，上述因素应被纳入监测体系，并在评估干预措施时予以考量。