The objective of this study was to evaluate the effect of growth phase of Amaranthus hypochondriacus on chemical composition and digestibility of green plants. Plants were collected during the growing season according to the days since sowing. Amaranth plants show decent dry matter degradation after 24 hours in the rumen (in sacco method), from 70 to 84.0%. The NDF content in the plant increased during vegetation; the nitrogenous substance content ranged from 6.1 to 8.5% and starch content from 2.9 to 9.4% in dry matter. + Amaranth plants show decent dry matter degradation after 24 hours in the rumen (in sacco method), from 70 to 84.0%.