Pitt R E, Cross T L, Pell A N, Schofield P, Doane P H
Department of Agricultural and Biological Engineering, Cornell University, Ithaca, NY 14853, USA.
Math Biosci. 1999 Jul;159(2):145-63. doi: 10.1016/s0025-5564(99)00020-6.
Physiological systems models for ruminant animals are used to predict the extent of ruminal carbohydrate digestion, based on rates of intake, digestion, and passage to the lower tract. Digestion of feed carbohydrates is described in these models by a first-order rate constant. Recently, an in vitro gas production technique has been developed to determine the digestion kinetics in batch fermentation, and nonlinear mathematical models have been fitted to the cumulative gas production data from these experiments. In this paper, we present an analysis that converts these gas production models to an effective first-order rate constant that can be used directly in rumen systems models. The analysis considers the digestion of an incremental mass of substrate entering the rumen. The occurrence of passage is represented probabilistically, and integration through time gives the total mass of substrate and total rate of digestion in the rumen. To demonstrate the analysis, several gas production models are fitted to a sample data set for corn silage, and the effective first-order rate constants are calculated. The rate constants for digestion depend on ruminal passage rate, an interaction that arises from the nonlinearity of the gas production models.
反刍动物的生理系统模型用于根据摄入、消化和进入下消化道的通过率来预测瘤胃碳水化合物的消化程度。在这些模型中，饲料碳水化合物的消化由一级速率常数来描述。最近，已开发出一种体外产气技术来测定分批发酵中的消化动力学，并且已将非线性数学模型拟合到这些实验的累积产气数据中。在本文中，我们进行了一项分析，将这些产气模型转换为一个有效的一级速率常数，该常数可直接用于瘤胃系统模型。该分析考虑了进入瘤胃的增量底物的消化。通过概率表示通过率的发生，并随时间积分得出瘤胃中底物的总质量和总消化率。为了演示该分析，将几个产气模型拟合到玉米青贮饲料的样本数据集，并计算有效的一级速率常数。消化的速率常数取决于瘤胃通过率，这种相互作用源于产气模型的非线性。
