Development of a mechanistic model of liver metabolism in the lactating cow

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Abstract

In order to accurately predict nutrient requirements and utilization in ruminants, an assessment of hepatic nutrient utilization must be made. A mechanistic, dynamic, deterministic model of liver metabolism was constructed to integrate available data toward this end. The objective of the modeling exercise was to develop a mechanistic model of ruminant liver metabolism, based on known metabolic pathways, which was capable of predicting whole-organ metabolism and simulating 14C-radiotracer kinetics. The program was written in the Advanced Continuous Simulation Language and run on a VAX computer. A fourth-order Runge-Kutta procedure was used for numerical integration. Development of kinetic arguments and subsequent parametrization relied heavily on in-vivo input: output data and underlying biochemistry.

The model was evaluated using a combination of behavioral analyses, sensitivity analyses, and challenges from independent data sets.

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    Present address: US Department of Agriculture, Agricultural Research Service, Roman L. Hruska US-Meat Animal Research Center, Clay Center, Nebraska 68933, USA.

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