The nutritive value of forages for ruminants highly depends on the ratio between cell content and cell walls and on the ability of the rumen microorganisms to degrade the plant cell walls (Waldo, 1986). The primary function of the NDF fraction in ruminant diets is to provide energy for microbial synthesis of the short chain fatty acids produced during fermentation, but also to secure rumen function and animal health by adding structural value to the diet (Mertens, 1994). The utilization of the fibre fraction in ruminant diets varies highly within and between forage types and is highly influenced by associated effects (Stensig and Robinson, 1997). Analysis of the content of fibre in ruminant feeds is based on the NDF analysis (Van Soest et al., 1991). The detergent system is a rapid procedure for determining the insoluble cell wall matrix and estimating its major subcomponents, as hemicellulose, cellulose and lignin can be determined from NDF, ADF and ADL analysis (Van Soest, 1994). While extensive grassland will still continue to be the most important form of management in the world, intensive grassland will continue to evolve with improved forage quality and yield of other forage crops, making a greater contribution to such systems. Moreover, treatment and breeding of cereal and protein crop straws will increase their feeding value, so that they will possibly contribute more to nutrient supply from grassland systems in the future.