The objectives of this work were to validate the predictionsbased on the estimates of the ruminal nutrient dynamics and on the microbialgrowth in the rumen, using equations of the Cornell Submodel system relativeto the gastrintestinal tract. Four Holstein - Zebu steers, with 300 kg liveweight, rumen and abomasal cannulated were allotted to 4x4 latin square design.The experimental animals received sugar cane based diets, supplemented withtwo nitrogen sources (urea or poultry litter) and two yeast levels (0 or 10g / d), being constituted 2x2 factorial arrangement. The indigestible neutraldetergent fiber (NDF) and chromium mordant sugar cane NDF were used as internaland external markers to estimate the daily fecal production and the ruminalparticle passage rates. The dynamics of the nutrients was based on the determinationof the total nitrogen and the abomasal nitrogen flows of microbial origin andtotal carbohydrate digested in the rumen. The microbial yield was not influencedby nitrogen sources or by Saccharomyces cerevisiae. The Cornell systemoverestimated the total ruminal carbohydrates digestion and the nitrogen flowof microbial origin and underestimated total nitrogen flow in the abomasum.
