Steer performance on Panicum maximum (cv. Mombaca) pastures under two grazing intensities

The objective of this study was to evaluate animal performance in Mombaca guineagrass (Panicum maximum Jacq.) pastures under intermittent grazing associated with two post-grazing heights (30 and 50 cm) and a pre-grazing height of 90 cm. A completely randomised block experimental design was employed, with two treatments and three replicates. The pastures were evaluated pre- and post-grazing grazing, to determine the herbage mass, percentage of leaf, stem and dead material and nutritive value. The stocking rate (expressed in animal unit, AU = 450 kg liveweight) was adjusted twice a week, and the animals were weighed every 28 days. The average grazing frequencies were 33 and 40 days, respectively, for 50 cm and 30 cm of residue pastures to reach the pre-grazing target (90 cm). The forage accumulation rate and pre-grazing herbage mass were similar for pastures with post-grazing heights of 30 and 50 cm. However, 50 cm of residue in the pasture resulted in greater pre-grazing leaf percentage and nutritive value and a lower percentage of dead material than did 30 cm of residue, and, consequently, a greater herbage intake (2.6 and 2.0 kg of dry matter/100 kg liveweight, respectively). The stocking rate was greater in the pastures with 30 cm of residue (6.7 AU/ha) than in those with 50 cm (5.1 AU/ha). However, the average daily gain was greater for the 50-cm (655 g/steer. day) than for the 30-cm (390 g/steer. day) post-grazing height, resulting in a greater animal production of 1070 versus 635 kg/ha, respectively. Thus, under intermittent grazing, Mombaca guineagrass should be managed using a 50-cm post-grazing height.