Development of a mathematical model to predict sizes and rates of digestion of a fast and slow degrading pool and the indigestible NDF fraction and implicationsfor feed intake

摘要

NDF is a non-uniform fraction with multiple pools.Later points in the fermentation curve, even if not biologically relevant for the cow, explain the non-uniformity and result in a more accurate and precise single weighted rate of NDF digestibility.The fast, slow and indigestible pools and respective rates can be estimated using a minimum of time points from in vitro NDFD data and a forage-group specific ratio iNDF/(ADL/NDF) to obtain the indigestible portion.Measures of pools and rates can be used to help explain cow intake behavior or to compare forages, especially when chemical analyses show forages to be similar.Estimations of the slow pool and its rate along with the size of the iNDF fraction can theoretically be linked to effects on dry matter intake and passage by increasing the bulk of the diet (rumen load). Indigestible NDF is determined by partly by lignin content and also cross-linking of lignin and carbohydrates through factors (light, heat, water) established during plant development