The research was carried out aiming to evaluate the influence of irrigation on total dry matter (TDMA) and green dry matter availability (GDMA) and on residual dry matter (RDM), forage height, forage density (FD), leaf percentage and chemical composition of leaf blades of the Napier grass and Mombaça grass. The treatments were the combinations of the two grasses and two irrigation levels (presence and absence). The irrigation supplied the previous ten-year mean evapotranspiration (ET0). It was adopted the rotational grazing, with grazing period of four days, rest period of 32 days and variable stocking, with grazing pressure of four kg of leaf dry matter per 100 kg live weight. Irrigated forages, in relation to non irrigated, and Napier grass, in relation to Mombaçagrass, showed higher TDMA, GDMA and RDM in both seasons of the year. Mombaça grass showed higher response to irrigation in TDMA and GDMA than Napier grass. During the dry season, irrigation increased percent of leaves, forage height and forage density. Napier grass, irrigated or not, in both seasons, was taller, showed lower proportion of leaves, but did not differ from Mombaça grass with respect to density. During the rainy season, irrigated forages were taller, but did not differ from the non irrigated ones regarding to percent of leaves and density. Irrigation had no influence on organic matter (OM), crude protein (CP) and neutral detergent fiber (NDF) content of forages. Napier grass, irrigated or not, had higher CP and lower OM and NDF than Mombaça grass, in both seasons.
forage quality; irrigated pastures; tropical grasses
