Nutritional evaluation of diets. Simulation model of digestion and passage of nutrients through the rumen-reticulum

Abstract

To evaluate the nutritional behaviour of simple and complex diets provided under different feeding regimes, a stochastic, dynamic and predictive simulation model was developed. Feed fractions, considered in the model were soluble non-structural carbohydrates (SNSC), insoluble non-structural carbohydrates (INSC), INSC degradation rate ( kd INSC), fractional passage rate ( kp), neutral detergent fibre (NDF), NDF potentially digestible (PNDF), PNDF degradation rate ( kd PNDF), soluble crude protein (SCP), insoluble crude protein (ICP), ICP potentially degradable (PICP), and PICP degradation rate ( kd PICP). Animal characteristics considered in the model, were live weight and physiological status (lactation and/or pregnancy). Variables inherent to management practices were amounts and schedule of DM offered to the animals. The model was subjected to validation for a wide range of experimental conditions. Predictions of total DM and forage DM intakes (and therefore the estimate of the substitution of forage for concentrate) had an R 2 = 0.95 and 0.92, respectively. Prediction of NDF digestibility had an R 2 = 0.61 in a smaller range of experimental conditions.