H.R. Conrad

A theoretically-based model for predicting total digestible nutrient values of forages and concentrates

A model using concentrations of neutral detergent fiber (NDF), lignin, crude protein (CP), ash, fatty acids or ether extract, and acid and neutral detergent insoluble crude protein, was developed for predicting total digestible nutrients (TDN) of feeds. The model incorporates theoretical digestion coefficients for CP, lipid, and non-fiber carbohydrate. Digestibility of NDF was estimated using a surface area model based on the lignin encrustation theory. The digestible amount of each nutrient was summed and then a term describing metabolic fecal TDN was subtracted. The model was tested on an independent set of 248 feeds (including forages and concentrates). The mean square error for all feeds was 61 g TDN kg−1 dry matter which is comparable with the error term for in vivo digestion data. The model was equally accurate and precise for forages and concentrate feeds.