Dynamics of Herbage and Plant Part Accumulation in Pastures of Xaraes Palisadegrass [Brachiaria brizantha Cv. Xaraes] Under Rotational Stocking.

In pastures under rotational stocking, the characteristics of pregraze forage may help understand animal intake behavior and performance.  In addition, if characterized during the regrowth (rest) period, it allows for inferences on patterns of plant part proportion and sward structure changes during forage accumulation.  The objective of this research was to describe comparatively the dynamics of total herbage as well as plant part accumulation in pastures of Xaraés palisadegrass [Brachiaria brizantha cv. Xaraes] subjected to rotational stocking managements, defined either by pre-graze light interception (LI) by the canopy (95% or 100% LI) or calendar days (28d). Pre-graze forage mass (FM) was highest (4800 kg DM ha^-1) for the 100% LI pastures. Pastures grazed at 95% LI and 28-d resulted in similar pre-graze FM in the spring (2150 kg DM ha^-1), both lower than that of the 100%-LI treatment. Grazing at 95% LI resulted in higher leaf percentage in pre-graze forage (88.5%), although total pre-graze FM was lower. Forage produced in paddocks grazed at 100% LI had lower (81.6%) leaf percentage pre-graze, indicating that the higher forage accumulation in that treatment was a result of higher stem elongation, likely due to light competition within the canopy. Rest periods beyond the point where swards achieved 95% LI (100% LI or 28-d during the summer) resulted in higher accumulation and higher pre-graze FM, although this corresponded mainly to large amounts of stem and dead material, which could negatively affect the nutritive value of forage produced and animal performance. Results  suggest that 95% LI as the best grazing strategy. Grazing management based on calendar days, although easier in terms of planning, reduce efficiency of utilization of herbage produced. Under rotational stocking, Xaraes palisadegrass should be grazed between 30 (start) and 15 cm (end) of height in order to avoid excessive stem accumulation.