Bauer et al., 2008. Rev. Bras. Zootec., 37 (1): 9-17

It was evaluated the effect of anatomical characteristics and tissue lignification sites on the leaf blade nutritive value of four grasses sampled during the dry and rainy season. Fresh samples of the two last expanded leaf blades on the tiller tops of molassesgrass (Melinis minutiflora Pal. De Beauv), signalgrass (Brachiaria decumbens Staph.), sapegrass (Imperata brasiliensis Trin.) and, jaraguagrass (Hyparrhenia rufa (Nees) Staph.) were collected in the rainy and dry seasons. These samples were evaluated according to anatomical characteristics using light and scan microscopy (proportion of xylem and sclerenchyma tissues), chemical composition and in vitro dry matter digestibility (IVDMD). The experimental data were submitted to statistical analysis appropriate to the completely random design, in the factorial arrangement with three replications per treatment. The same pattern of tissue proportion and IVDMD values were observed for molassesgrass and signalgrass, as well as for sapegrass and jaraguagrass. The seasons of the year influenced the IVDMD and the concentrations of the cell wall components, but their effect on the leaf blades anatomical characteristics was inconsistent. Significant and negative correlation coefficients were observed between the IVDMD and the proportions of lignified vascular bundle sheath, sclerenchyma and phloem as well as with NDF, ADF and lignin contents of the leaf blades.