The objective was to evaluate the kinetics of degradation in the first compartment (C1) of llamas of the dry matter(DM) of forage F. dolichophylla harvested at 3, 6, 9, 12 and 15 weeks of growth during two seasons (rainy and dry ).The degradation kinetics of crude protein (PC), neutral detergent fiber (NDF) and acid detergent fiber (ADF) wereevaluated only in the rainy season. In situ degradation was described by the equation of Orskov et al., (1980) D = a +b (1-exp-ct). A completely randomized block design with a 2 x 5 factorial arrangement was used for the MS. The rate (c) 3.24% h-1, intercept of the curve (a) 22.22%, and the degradation potential of MS (a + b) 91.32%, were notaffected (P> 0.05) by the time, age and interaction. However, the effective DM degradation (estimated with a flowrate of k = 2% h-1) was affected (P 0.05) by the age of growth. However, the potentialand effective degradation (k = 2% h-1) was influenced by the age of growth, ranging from 97.7 to 90.1%, 86.0 to80.8%, and from 72.4 to 71.9% from 3 to 15 weeks of increase. The effective degradation of PC, NDF and ADF wasaffected (P <0.05) by the age of growth, decreasing from 88.6 to 63%, 63.5 to 57.1%, and from 51.7 to 40.3% from3 to 15 weeks of growth. It is concluded that the accelerated degradation of the protein at early hours, and lowdegradation of cell walls causes an imbalance in the availability of protein and absence of energy.