A study was carried out to evaluate the variability of the in situ ruminal effective degradability (DER) of dry matter (MS) and organic matter (MO) of leaves, stems and complete plant of three varieties of C. purpureus at four regrowth ages. For DER of MS, the smaller variance, standard deviation (DE) and coefficient of variation (CV) were obtained to the 100 days in leaves and stems (in MO it was to 80 days) and 80 days for the complete plant (in MO it was of 120 days). The minimum ranks of DER agreed to the 120 days for all the fractions, the maximum ranks corresponded at the age of 80 days in leaves, 60 days in stems, 100 days for the complete plant. The varieties CT-603 and CT-605 presented the greater DER. It concluded that the age of regrowth affects the DER of MS and MO in the soil and climatic conditions of Valle del Cauto, is recommended to use the plants between 80 and 100 days of regrowth
