The objectives of the present work were to characterizate and determinate the parameters estimates related to the ruminal degradation kinetics of the carbohydrates in extrusa samples from animals maintained in a natural pasture of the Zona da Mata (MG) region, during the rainy and dry seasons of the year. To obtain representative samples, four esophageal fistulated steers were used in two experimental periods during the rainy season, and three of these animals were used in two experimental periods during the dry season, in the year of 1996. The carbohydrate fractionation according to the Cornell system was done, and the neutral detergent fiber (NDF) degradation rates were obtained from the in vitro degradation profiles of this component. The potentially degradable (B₂) and undegradable (C) fractions of NDF corrected for protein and ash, the dynamic lag rates, the degradations rates, and the specific growth rates of microorganism upon fraction B₂ were obtained, as well as thedegradability coefficients and the rumen fill effect of NDF. As aresult, it was possible to observe that the non-structural carbohydrates comprised a minor fraction of the total carbohydrates in the pasture samples in both seasons. The structural carbohydrates were responsible by the total carbohydrate increase in the extrusa from the rainy to the dry season; nevertheless, due to the C fraction increase and to the lower specific microorganism growth rates during the dry season, it was noticeable the reduction of the extrusa NDF degradability and its increased rumen fill effect.