In the study, 2 grasses and 2 legumes were harvested at 2 stages of growth. Duplicate samples were incubated in sacco in the rumen of 3 mature, fistulated cows for 2, 4, 8, 16, 24, 48 and 72 hours, and the degradability of DM and nitrogen was measured. Degradability data were fitted with a Gompertz model, which offers the opportunity of studying two aspects of rumen degradation: degradation kinetics, represented as cumulative curves and degradation rate kinetics. The synchronicity in the release of nitrogen and dry matter or structural carbohydrates was calculated from the ratio between the quantity of nitrogen and dry matter or fibre degraded per unit time, using the first derivative of the Gompertz equation. This provided a dynamic description of the degradation process for each forage which would allow the combination of feeds in a ration to maintain these ratios constant throughout the rumen digestion process.