Colorimetric method as alternative to chromium (III) quantification in cattle feces

ABSTRACT. One of the main factors to establish productivity of grazing cattle is the estimation of forage intake. For this, the most widely used technique is based on the estimation of fecal output using chromium dioxide as external marker. However, quantification can be expensive and sometimes not precise due to the methodology used for this purpose. Therefore, the aim of this study was to validate the colorimetric method for chromium quantification and to implement it in the estimation of fecal output in grazing cattle. The temperature, the digestion time and the wavelength for the measurement were evaluated. The method was validated for selectivity, linearity, detection and quantification limits, precision, accuracy, and stability. Results showed that temperature and digestion time are critical to improve sensitivity and quantification limits. The validation demonstrated that the method is suitable for the quantification of Cr2O3 in a wide range of concentrations, being statistically comparable with a reference method, and offering a reliable low cost and easy to implement alternative, to estimate fecal output in bovine digestibility studies.

摘要 影响放牧肉牛生产性能的核心因素之一是饲草采食量的估算。为此，当前应用最广泛的技术是以二氧化铬作为外源性标记物来估算粪便排泄量。但该方法因所用检测手段的局限，往往存在检测成本较高且精度不足的问题。因此，本研究旨在验证用于铬元素定量的比色法，并将其应用于放牧肉牛的粪便排泄量估算中。研究评估了检测过程中的温度、消解时长与测定波长三项参数。本方法从选择性、线性度、检测限与定量限、精密度、准确度以及稳定性六个维度进行了方法学验证。结果表明，温度与消解时长是提升方法灵敏度与优化定量限的关键参数。方法学验证结果显示，该方法可适用于宽浓度范围内的三氧化二铬（Cr₂O₃）定量，经统计学分析其检测结果与参考方法无显著差异，可为肉牛消化试验中的粪便排泄量估算提供一种低成本、易操作且结果可靠的替代方案。