The present study aimed at determining the chemical composition and digestibility of leaves (sheath+blade) and stems belonging to Axonopus scoparius and Axonopus fissifolius cultivars, during two growing stages. A completely randomized design with two treatments (6 and 20 weeks of growing) and five replicates were used. The nylon bag technique was used to determine the digestion kinetics and the Near Infra Red Spectroscopy (NIRS) technique to determine the bromatological composition. Tissue degradation was histologically observed after the incubation of small stem and leaf portions in cattle ruminal liquid. With mature age, it was observed that Axonopus scoparius cultivars reduced the effective degradability, which was related to cell wall thickening and increased lignified tissue area. The level of crude protein was the parameter mostly affected as species grew older. Leaf fractions (limbo, keel and sheath) of Axonopus fissifolius showed large areas of lignified tissues, resulting in lower digestibility rates as compared to Axonopus scoparius. The Axonopus scoparius "verde" cultivar, proved more susceptible to ruminal digestion than "roxo" cultivar, whereas no differences were observed in Axonopus fissifolius cultivars. The stem was the part of plant presenting greater reduction in digestion as compared to the leaf portion.
digestibility; forage; lignin; NDF; NIRS; ruminants
