Department of Virology, Parasitology and Immunology, Salisburylaan 133, 9820 Merelbeke, Ghent University, Belgium.
J Dairy Sci. 2012 Jun;95(6):2977-87. doi: 10.3168/jds.2011-4719.
Current control practices against gastrointestinal nematodes in dairy cows rely strongly on anthelmintic use. To reduce the development of anthelmintic resistance or disposition of drug residues in the environment, novel control approaches are currently proposed that target anthelmintic treatment to individual animals instead of the whole herd. However, such selective treatment strategies come with additional costs for labor and diagnostics and, so far, no studies have addressed whether they could be economically sustainable. The objectives of this study were to (1) investigate the economic effects at farm level of whole-herd versus more selective anthelmintic treatment strategies in adult dairy cows, and (2) determine how these economic effects depend on level of infection and herd size. A Monte Carlo simulation, fed by current epidemiological and economical knowledge, was used to estimate the expected economic effects and possible variation of different control strategies under Belgian conditions. Four treatment strategies were compared with a baseline situation in which no treatments were applied: whole herd at calving (S1), selective at calving with (S2) or without (S3) treatment of the first-calf cows, and whole-herd when animals are moved from grazing to the barn in the fall (housing treatment, S4). The benefit per lactation for an average dairy herd varied between -$2 and $131 (average $64) for S1, between -$2 and $127 (average $62) for S2, between -$17 and $104 (average $43) for S3, and between -$41 and $72 (average $15) for S4. The farmer's risk associated with any treatment strategy, as indicated by the width of the 95% credible intervals of economic benefit of anthelmintic treatment, decreased with increasing level of exposure, as assessed by bulk tank milk ELISA. The order of the different strategies when sorted by expected benefit was robust to changes in economic input parameters. We conclude that, on average, strategies applying anthelmintic treatment at calving outperform a strategy applying treatment at housing. Within the strategies that applied treatment at calving, more selective treatment strategies can be economically sustainable. However, given the large variation in possible benefits within each treatment strategy, decision support systems are needed to account for the multitude of cow, epidemiological, and economic factors that determine the economics of nematode control and select the optimal treatment strategy for a specific farm.
当前，奶牛养殖业对抗胃肠道线虫的主要方法是驱虫药物的使用。为了减少抗寄生虫药物的耐药性发展或药物残留对环境的影响，目前提出了一些新的控制方法，旨在针对个体动物而非整个畜群进行驱虫治疗。然而，这种有针对性的治疗策略会增加劳动力和诊断方面的成本，而且到目前为止，还没有研究探讨其是否具有经济可持续性。本研究的目的是：（1）调查在比利时，针对成年奶牛采用全群驱虫和更具针对性的驱虫治疗策略时农场层面的经济影响；（2）确定这些经济影响如何取决于感染水平和畜群规模。本研究使用了蒙特卡罗模拟方法，根据当前的流行病学和经济学知识来估计不同控制策略的预期经济效果和可能的变化。与不进行任何处理的基线情况相比，比较了四种处理策略：产犊时全群处理（策略 1，S1）、产犊时选择性处理（策略 2，S2）或不处理（策略 3，S3）初产奶牛、秋季动物从放牧转入畜舍时进行全群处理（畜舍处理，S4）。对于一个平均规模的奶牛场，每头泌乳奶牛的效益变化范围在-2 美元至 131 美元之间（平均为 64 美元），策略 1 为-2 美元至 127 美元（平均为 62 美元），策略 2 为-17 美元至 104 美元（平均为 43 美元），策略 3 为-41 美元至 72 美元（平均为 15 美元），策略 4 为-41 美元至 72 美元（平均为 15 美元）。随着牛奶中抗体 ELISA 检测的群体暴露水平的增加，与任何处理策略相关的农民风险（以驱虫治疗的经济效益 95%可信区间的宽度来衡量）降低。当按预期收益对不同策略进行排序时，这种排序在经济投入参数变化时仍然是稳健的。综上，平均而言，在产犊时进行驱虫治疗的策略优于在畜舍时进行驱虫治疗的策略。在产犊时进行驱虫治疗的策略中，更具针对性的治疗策略在经济上可能是可持续的。然而，鉴于每种治疗策略中可能产生的效益存在很大差异，需要决策支持系统来考虑决定线虫控制经济学的众多牛、流行病学和经济因素，并为特定农场选择最佳的治疗策略。
