The objective of this study was to evaluate the management of the Urochloa
brizantha cv. Piatã grass. Two tests were performed for the evaluation. The first
test consisted in monitoring the evolution of the Piatã grass during 49 days, by
the evaluating of tillering, forage biomass, leaf area index (IAF), interception of
photosynthetically active radiation (IRFA), relative growth rate (TCR), and net
assimilation rate (TAL). The pasture was fertilized with 40 and 80 kg ha-1 of
nitrogen and potassium, respectively. The second test was to evaluate the
termination of beef cattle managed in intermittent system, with entry height fixed
(35 to 40 cm), and the moment of exit determined by three residues of leaf blade
(2, 4 and 6 cm). Morphogenic and structural characteristics were monitored
during two growing seasons (rainy and drought-rainy), and the agronomic and
chemical characteristics of the forage were studied during five grazing cycles,
using 18 animals. These animals were managed in 4.8 ha of Piatã grass divided
in six modules with four pickets of 0.2 ha. The ingestive behavior and the
displacement pattern of the animals were evaluated in two conditions (entry and
exit of animals). The height of the canopy showed linear growth, reaching 70.25
cm at 49 days in the highest fertilization. The tillering decreased in the last three
weeks. IRFA evolved asymptotically, with maximum values of 94% in both
fertilizations. TCR and TAL showed decreasing asymptotic evolution, because of
the high proportion of stem in the canopy, during the 49 days. The morphogenic
characteristics were not influenced by the treatments and seasons, which
promoted little change in the structural characteristics, only in the mean sheath
length (CMB) in the season and population density of tiller (DPP). The highest
value found for CMB, at the rainy station 210.37 mm versus 175.89 mm, for the
transition (drought-rainy). DPP presented the lowest value (680 tiller m-2
) with the
largest removal (2 cm). The residue of leaf blade had little effect on animal
behavior, being more influenced by the conditions of the pasture, entry and exit
of animals. This result was found, because the greater forage mass at the entry,
the animals reduced grazing time, time per meal, number of bites, total number
of morsels, total number of seasons, total number of steps, and increased the
duration time of meal interval, in addition to the time per food season. Animal
performance was directly influenced by RLF, with a lower daily mean gain (ADG)
at 2 cm (0.575 kg animal-1 day-1
) and higher at 6 cm (0.753 kg animal-1 day-1
). In
part, this fact was associated to the greater displacement of the animals in
pastures with greater intensity of exit. However, the lowest weight gain was
compensated by the higher stocking rate (TL) for this strategy (6.60 UA), in
relation to the one with the highest residue of leaf blade post-grazing (5.32 AU),
which maintained the constant weight gain per area (615.30 kg ha-1
), for the
managements. Fertilization changes the window of management of the Piatã
grass, which can be managed with the three evaluated post-grazing strategies
(2, 4 and 6 cm), provided that the rest period be variable, respecting the plant
growth.
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