Chemical composition and physical characteristics of diet influences its optimal utilization in dairy cow. Neutral detergent fiber measures the chemical characteristics, but not the physical characteristics of fiber such as particle size and density (Mertens, 1997). Both the amount and physical form of fiber are important in the diet of lactating dairy cow for maintaining normal milk fat content, chewing and digestive activities. A sufficient supply of long particles or NDF must be included in the ration to increase chewing activities, maintaining the rumen pH and providing an optimal rumen environment in order to avoid metabolic disorders. Current NRC guidelines (NRC, 2001) have proven useful information in defining animal requirements and feed composition but do not provide detailed recommendation on physical form of ration. The objective of this experiment was to determine the effect of lucerne particle size on feed intake and digestibility in dairy cow in early lactation period.