Analysis of forage fiber and cell walls in ruminant nutrition

Analysis of the fiber or cell wall present in forages is of major concern in ruminant nutrition because diets often contain large amounts of forage, and the fiber fraction affects both feed intake and animal performance. Traditional extractive, gravimetric methods such as crude fiber and neutral detergent fiber recover variable amounts of the plant cell wall, but they remain popular because of their ease of use and the large feed data bases available for these methods. More intensive chemical methods utilizing chromatography and spectrometric analysis provide greater detail on cell wall composition and structure, but they have been used little in ruminant nutrition. Lignin analysis has remained problematic because no definitive reference method exists. Recently attention has focused on the measurement of lignin composition and cell wall phenolic acids; however, these methods have yet to be widely adopted in ruminant nutrition. The detergent fiber methods have been semi-automated to increase sample handling capacity. Near-infrared spectroscopy is routinely used for prediction of fiber concentration in forages and has greatly increased the ease of obtaining fiber analysis of forage samples. Widespread adoption in ruminant nutrition of the more sophisticated methods of cell wall analysis is unlikely to occur until these methods can be demonstrated to improve diet formulation and prediction of animal performance.