Owczarzak Eric J, Grotenrath Nick, Carlson Hannah, Mamedova Laman, Bradford Barry J, Abuelo Angel
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824.
Department of Animal Science, College of Agriculture and Natural Resources, Michigan State University, East Lansing, MI 48824.
JDS Commun. 2024 Feb 1;5(4):344-349. doi: 10.3168/jdsc.2023-0520. eCollection 2024 Jul.
Vitamin E is essential in mitigating the impact of oxidative stress on periparturient dairy cows and neonatal calves. Therefore, it is essential to measure circulating vitamin E concentrations accurately. Currently, the only reliable method is an expensive and time-consuming procedure using liquid chromatography-mass spectrometry (LC-MS). However, a cheaper and faster method has been developed, which allows the quantification of circulating vitamin E through the use of a handheld fluorometric analyzer (HFA) called the vitamin E iCheck (BioAnalyt GmbH). Our objective was to compare the accuracy of the HFA to the reference LC-MS method for measuring vitamin E in bovine samples. A total of 177 samples collected for other studies were used: 98 newborn calf serum samples from a vitamin E supplementation study (including treated and control animals) and 79 whole-blood samples from cows 1 to 7 d postcalving. Vitamin E concentrations were measured on thawed calf serum and fresh cow EDTA blood using the HFA, following the manufacturer's instructions. Whole blood from cows was then centrifuged to obtain plasma. Vitamin E was also quantified in calf serum and cow plasma at the Michigan State University Veterinary Diagnostic Laboratory using LC-MS. Calf and cow results were analyzed separately because they represent different biological matrices and physiological times. In each dataset, results between the HFA and LC-MS determinations were compared using Passing-Bablok regressions and Bland-Altman plots. The HFA showed a poor linear relationship with LC-MS for calf serum and cow plasma (intercept = 0.33 and 0.67 μg/mL, respectively). The HFA unreliably estimated vitamin E, with a mean bias of -3.2 and 0.6 μg/mL for calves (vitamin E concentration range: 0.28 to 30.75 μg/mL) and cows (0.8 to 5.88 μg/mL), respectively. Moreover, 40.4% of the calf samples read below the linear range of acceptable results for the HFA, making it unsuitable for this age group. Hence, under the conditions of our study, the HFA yielded unreliable results and cannot be recommended for field use.
维生素E对于减轻氧化应激对围产期奶牛和新生犊牛的影响至关重要。因此，准确测量循环维生素E浓度至关重要。目前，唯一可靠的方法是使用液相色谱-质谱联用仪（LC-MS）的昂贵且耗时的程序。然而，已经开发出一种更便宜、更快的方法，该方法可以通过使用一种名为维生素E iCheck的手持式荧光分析仪（HFA，BioAnalyt GmbH公司）来定量循环维生素E。我们的目标是比较HFA与参考LC-MS方法在测量牛样本中维生素E时的准确性。总共使用了为其他研究收集的177个样本：来自一项维生素E补充研究的98份新生犊牛血清样本（包括处理组和对照组动物）以及79份产后1至7天奶牛的全血样本。按照制造商的说明，使用HFA对解冻后的犊牛血清和新鲜奶牛乙二胺四乙酸（EDTA）抗凝血中的维生素E浓度进行测量。然后将奶牛的全血离心以获得血浆。在密歇根州立大学兽医诊断实验室，也使用LC-MS对犊牛血清和奶牛血浆中的维生素E进行了定量。犊牛和奶牛的结果分别进行分析，因为它们代表不同的生物基质和生理时期。在每个数据集中，使用帕辛-巴布洛克回归和布兰德-奥特曼图比较了HFA和LC-MS测定结果之间的差异。对于犊牛血清和奶牛血浆，HFA与LC-MS显示出较差的线性关系（截距分别为0.33和0.67μg/mL）。HFA对维生素E的估计不可靠，犊牛（维生素E浓度范围：0.28至30.75μg/mL）和奶牛（0.8至5.88μg/mL）的平均偏差分别为-3.2和0.6μg/mL。此外，40.4%的犊牛样本读数低于HFA可接受结果的线性范围，这使其不适用于该年龄组。因此，在我们的研究条件下，HFA得出的结果不可靠，不建议在现场使用。
