Abstract
The effects of defoliation frequency (21, 28, 35 and 42 days) and defoliation intensity (20, 30 and 40 cm above the ground) on green dry matter (GDM) yield, and chemical composition of Megathyrsus maximus cv. Tamani were evaluated under natural field conditions at the Roraima´s savannas. Defoliation regimes affect productivity and chemical composition of M. maximus cv. Tamani forage. The decrease in the pasture defoliation frequency and intensity improved the accumulation of forage, however it reduces the tissue concentrations of N, P, Ca, Mg and K. Irrespective of defoliation frequencies, the highest levels of N (25.31 g kg-1), P (2.11 g kg-1), Mg (2.78 g kg-1) and K (21.13 g kg-1) were recorded for the defoliation intensity at 40 cm above the ground, except for Ca (4.31 g kg-1), where the greatest concentration was obtained with defoliations at 30 cm above the ground. The use of defoliation frequency around 32 days and defoliation intensity of 28 cm above the ground can be considered adequate for the management of pastures of M. maximus cv. Tamani, in order to provides higher forage productivity and quality, regrowth vigor, larger efficiency of forage utilization, greater tissue renewal and canopy structure more favorable to grazing.
Highlights
In Roraima, cattle ranching is a of the main economic activities and the cultivated pastures represent the main forage resource for the feeding of the herds
In this work were avaluated the effects of defoliation frequency and itensity on forage accumulation and chemical composition of Megathyrsus maximus cv
The effect of the defoliation intensity was adjusted to the quadratic regression model (Y = 1,481 + 204.85 X - 3.1752 X2 [R2 = 0.94]) and the maximum value was estimated at 32.2 cm above the ground (Table 1)
Summary
In Roraima, cattle ranching is a of the main economic activities and the cultivated pastures represent the main forage resource for the feeding of the herds. The use of continuous grazing or minimum rest periods, high intensities defoliation and non-replacement of nutrients removed via animal production are factors that contribute to low availability and quality of forage, with negative effects on the zootechnical performance of animals (Costa et al, 2007). Productivity and longevity of forage grasses derive from their capacity reconstitution and maintenance of the leaf area after defoliation, which affects the structure of the canopy, determining its speed of growth (Pereira, 2013).
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