United States Department of Agriculture, Agricultural Research Service, Appalachian Farming Systems Research Center, 1224 Airport Rd., Beaver, WV 25813, USA.
Vet Parasitol. 2012 Aug 13;188(1-2):60-7. doi: 10.1016/j.vetpar.2012.03.007. Epub 2012 Mar 15.
Gastrointestinal nematode (GIN) parasites present an important limitation to ruminant production worldwide. Methods for quantifying infective larvae of GIN on pastures are generally tedious, time-consuming, and require bulky equipment set-ups. This limitation to expedient data collection is a bottleneck in development of pasture management practices that might reduce pasture infectivity. We modified a soil elutriator concept for extracting GIN larvae from fresh herbage samples. Elutriators were constructed from readily available parts and compared to the Baermann funnel sedimentation method for larvae extraction. More samples could be extracted per day in the elutriator than in a Baermann unit with extraction times of 8 min versus 24h, respectively. Accuracy, measured as maximum recovery of larvae seeded onto herbage samples, did not differ between extraction methods (62.3 vs. 69.8% for elutriator and Baermann, respectively, P>0.05). Larvae recovery from herbage in elutriators showed a strong log(e) relationship with extraction time (r(2)>0.98), which will allow development of accurate correction factors for specific herbages to predict total larvae densities at extraction times less than those needed for maximum recovery. An extraction time of 8 min per sample gave the best compromise of speed, accuracy, and precision as measured by regression confidence bands and root mean square error of analysis of variance. Precision of the elutriator extraction for pasture samples was comparable to published methods and was not affected by forage species or canopy strata. The elutriator method was sensitive enough to detect differences in larvae density as small as 8 larvae g(-1) DM among pasture treatments. Elutriators extracted nematode larvae from herbage samples with accuracy and precision similar to existing methods, but did it much faster. Elutriation shows promise as a rapid method for extracting infective GIN larvae from pasture herbage.
胃肠道线虫（GIN）寄生虫对全球反刍动物生产构成了重要限制。定量分析牧场上感染性幼虫的方法通常繁琐、耗时且需要庞大的设备设置。这种对便捷数据收集的限制是开发可能降低牧场地感染性的牧场管理实践的瓶颈。我们修改了一种从新鲜草料样本中提取 GIN 幼虫的土壤淘析器概念。淘析器由现成的部件构建而成，并与贝曼漏斗沉淀法进行了幼虫提取比较。与 24 小时相比，淘析器每天可以提取更多的样本，提取时间分别为 8 分钟和 8 分钟。提取方法之间的准确性（以幼虫接种到草料样本上的最大回收率衡量）没有差异（分别为 62.3%和 69.8%）。淘析器中从草料中回收的幼虫与提取时间呈强烈的对数（e）关系（r(2)>0.98），这将允许为特定草料开发准确的校正因子，以预测在最大回收率所需时间以下的总幼虫密度。每个样本提取 8 分钟的时间是速度、准确性和精度的最佳折衷方案，这可以通过回归置信带和方差分析的均方根误差来衡量。淘析器提取牧场样本的精度与已发表的方法相当，并且不受草料种类或冠层层次的影响。淘析器的提取方法足够灵敏，可以检测到牧场处理之间小至 8 个幼虫 g(-1) DM 的幼虫密度差异。淘析器以类似于现有方法的准确性和精度从草料样本中提取线虫幼虫，但速度更快。淘析器有望成为一种从牧场草料中快速提取感染性 GIN 幼虫的方法。
