Effects of growing periods on digestion and chemical composition of elephant grass cultivars tissues

In the present work, the chemical composition changes and dry matter (DM) digestibility of three cultivars (Empase-307-Testo, Empase-309-Areia and Roxo) of elephant grass (Pennisetum purpureum Schumach.), were measured through a growing period of 126 days. The production and quality of tropical forage grasses were determined, in part. by the growing period. The plants showed greater height and dry matter accumulation. increasing the neutral detergent fiber (NDF) and lignin concentrations and substantially reducing DM and NDF digestibility levels, with longer growing periods. The stem contribution with the total DM production increased with time, reaching leaf:stem ratio of 35:65 % by the end of the growing period. At advanced grow th stage, even with similar lignin concentration. the stem digestibility was lower than that of leaves. The loss of quality measured as a decrease in the digestibility, observed in elephant grass at advanced growth stage, was related to the thickness and lignification of the cell wall, followed by a reduction in the leaf:stem ratio. Other factors, besides lignin, contributed for reducing digestibility of stem.