Gasbarre L C, Leighton E A, Bryant D
USDA, ARS, LPSI, Parasite Immunobiology Laboratory, Beltsville, MD 20705, USA.
Am J Vet Res. 1996 Feb;57(2):168-71.
To determine precision of a single fecal egg count, to evaluate the necessity of repeated testing to ascertain the number of parasite eggs found per gram of fecal material (EPG) of a given animal, and to infer the number of cattle that must be sampled to estimate the mean EPG value of a given herd.
Calves born in 4 successive years were tested for 3 consecutive days in May, July, and September to determine their fecal EPG value. Results were analyzed to determine important sources of variance in the EPG values.
427 Black Angus calves.
Nematode EPG values were determined by zinc sulfate flotation of fecal samples taken from the rectum. Variance components were estimated by restricted maximal likelihood procedures.
The largest source of variation in fecal egg counts arose from differences among calves. Variation associated with sampling within calf was larger than that associated with year of sampling or day when samples were taken. Repeatability of EPG determinations was between 0.4 and 0.7.
Collection of 3 replicate samples reduced variance associated with a single calf mean by 25 to 30%. Additional replication would further reduce the variance, but at a diminishing rate. To accurately estimate mean EPG for a herd, a randomly drawn sample should be similar in composition to the herd and include at least 1 animal from the high EPG group, which often constitutes 15 to 20% of the calves. To ensure that, on average, 95% of the samples drawn contain 1 or more animals with high EPG, the sample must include 15 to 20 animals within the grazing group under study.
确定单次粪便虫卵计数的精确度，评估对给定动物每克粪便物质（EPG）中发现的寄生虫卵数量进行重复检测的必要性，并推断为估计给定牛群的平均EPG值必须采样的牛的数量。
对连续4年出生的犊牛在5月、7月和9月连续3天进行检测，以确定其粪便EPG值。对结果进行分析，以确定EPG值变异的重要来源。
427头黑安格斯犊牛。
通过对从直肠采集的粪便样本进行硫酸锌漂浮法测定线虫EPG值。采用限制最大似然法估计方差成分。
粪便虫卵计数的最大变异来源是犊牛之间的差异。与犊牛内采样相关的变异大于与采样年份或采样日相关的变异。EPG测定的重复性在0.4至0.7之间。
采集3份重复样本可使与单个犊牛平均值相关的变异减少25%至30%。进一步增加重复次数将进一步降低变异，但降低幅度会逐渐减小。为准确估计牛群的平均EPG，随机抽取的样本在组成上应与牛群相似，且至少包括1头来自高EPG组的动物，该组动物通常占犊牛的15%至20%。为确保所抽取的样本平均有95%包含1头或更多高EPG动物，在所研究的放牧组内样本必须包括15至20头动物。
