Predicting the effect of lignin on the extent of digestion and the evaluation of alternative intake models for lactating cows consuming high NDF forages

imilar neutral detergent fiber (NDF) digestibility values were obtained at five specified time periods with a new labor-saving in vitro system (FBT) on four tropical and four temperate forages compared to a conventional in vitro system (CM). Rates of NDF digestion of Andropogon gayanus, Medicago sativa, and Panicum maximum were also similar. The FBT system was used to determine the maximum extent of digestion at 144 h on several tropical grass and legume species. These values were combined with temperate data to derive an equation to predict the indigestible NDF (INDF) in forage based on chemical composition.;Equations were developed to predict INDF from various indices of lignification (% of dry matter and NDF, and g lignin/kg NDF) by forage class (C;Data from 20 lactating cows consuming high NDF forage-based diets in Honduras were used to evaluate the DMI prediction accuracy of nine intake models. Cows consumed more forage as dietary NDF content increased. Consequently, the mean and variation in daily milk yield decreased with increasing dietary NDF content. The NDF intake from these tropical forages was greater than in previous studies in temperate ruminants. A composite intake model was devised that accounts for chemostatic and physical fill limitations on intake. In tropical settings for cows yielding...