CREATING A SYSTEM FOR MEETING THE FIBER REQUIREMENTS OF DAIRY-COWS

Current NRC recommendations for dairy cattle provide limited guidance to nutritionists for meeting the fiber and carbohydrate needs of lacta ting cows. The NRC provides only minimum recommendations for fiber and no accommodation for factors such as physical effectiveness of fiber, interactions with nonfibrous carbohydrates, or animal attributes, whi ch can affect the optimality of dairy rations. To be an improvement, a ny new system for meeting the fiber requirements of dairy cows must be based on 1) feed characteristics that can be defined and preferably b e determined quantitatively using routine laboratory methods and 2) an imal requirements that correspond to critical feed characteristics and vary with feeding situation, ration composition, and attributes of th e animal. Published data were used to develop coefficients for definin g the physical effectiveness or roughage value of feeds and the fiber requirements of dairy cows. Information in this paper is intended to p rovide practical guidelines for improving current fiber recommendation s and to serve as an idealized framework for future research on meetin g the fiber requirements of dairy cows. The system is based on NDF as the measure of total chemical fiber in feeds. Adjustments for the effe ctiveness of NDF in maintaining milk fat production and optimizing rum inal fermentation are based on the particle size and inherent characte ristics of NDF that affect chewing activity, ruminal pH, and milk fat production.