Department of Animal Sciences, College of Agriculture, Kansas State University, Manhattan, KS.
Department of Statistics, College of Arts and Sciences, Kansas State University, Manhattan, KS.
J Anim Sci. 2018 Nov 21;96(11):4611-4617. doi: 10.1093/jas/sky347.
Diet treatments were arranged in a split-plot design with the whole-plot consisting of 1 of 6 concentrations of dietary Cu (22 to 134 mg/kg total Cu) and the subplot using 1 of 2 sampling techniques (probe vs. hand grab). A total of 6 feeders per treatment were sampled using a brass open handle probe. The probe was inserted into the feeder 4 times to obtain a 900 g of sample. The hand-collected samples were obtained by inserting a bare hand into the feeder approximately 8 times to obtain a 900 g of sample. Within a feeder and sampling technique, subsamples (200 g) were created by using a sample splitting device. In addition to the 6 individual feeder samples, a subsample (33 g) from each individual feeder was pooled within dietary treatment and sampling technique to form a single composite sample (200 g). This process was repeated until 4 individual composite samples were created for each diet and sampling technique. Next, all samples were ground through a centrifugal mill and submitted for mineral analysis in duplicate for Cu, Zn, Ca, and P analysis. Results indicated variability when sampling feeders with a probe were reduced (P = 0.013) for Cu and marginally reduced (P = 0.058) for Ca when compared with hand-sampling. However, no evidence for differences was detected among sampling techniques for Zn and P for the individual feeder analysis. When samples were pooled from 6 feeders to form a single composite sample, there was no evidence for differences detected among sampling techniques for Cu, Zn, Ca, and P analysis. From these results, sampling frequency calculations were determined to assess sampling accuracy within a 95% confidence interval. Results indicated that the number of feeders or composite samples required to analyze was less for Cu, Zn, Ca, and P analysis when using a probe compared with a hand sampling. In summary, sampling with a probe is associated with less variability on an individual sample basis, but when individual samples are pooled to form a composite sample, there was no evidence for difference among sampling techniques. Our results suggest samples collected for these analyses with a probe and composited would be the best option to minimize variation and analytical costs.
饮食治疗采用裂区设计，主区为 6 种饲粮铜浓度（22 至 134 毫克/千克总铜）中的 1 种，副区为 2 种采样技术（探针与手工抓取）中的 1 种。每处理 6 个饲槽使用黄铜开放式手柄探针进行采样。将探针插入饲槽 4 次，获得 900 克样品。手工采集的样品是将裸露的手插入饲槽大约 8 次，获得 900 克样品。在一个饲槽和采样技术中，使用样品分割装置创建子样本（200 克）。除了 6 个个体饲槽的样本外，还从每个个体饲槽中抽取一个子样本（33 克），在饲粮处理和采样技术中进行混合，形成单个复合样本（200 克）。这个过程重复进行，直到为每种饲粮和采样技术创建 4 个个体复合样本。然后，将所有样品通过离心磨粉碎，并进行铜、锌、钙和磷分析的重复分析。结果表明，与手工采样相比，使用探针采样时，铜的变异性降低（P = 0.013），而钙的变异性略有降低（P = 0.058）。然而，在个体饲槽分析中，没有证据表明在锌和磷的采样技术之间存在差异。当将来自 6 个饲槽的样品混合形成单个复合样本时，在铜、锌、钙和磷分析中，没有证据表明在采样技术之间存在差异。根据这些结果，计算了采样频率，以评估在 95%置信区间内的采样准确性。结果表明，与手工采样相比，使用探针采样时，铜、锌、钙和磷分析所需的饲槽或复合样本数量较少。总之，探针采样在个体样本基础上的变异性较小，但当个体样本混合形成复合样本时，在采样技术之间没有证据表明存在差异。我们的结果表明，使用探针采集这些分析用的样本并进行混合是最小化变异和分析成本的最佳选择。
