Defoliation dynamics of Brachiaria brizantha pastures with distinct structural characteristics

Abstract

Although belonging to the same species, different Brachiaria brizantha varieties used for pasture vary significantly in their morphological structure. Therefore, this study starts from the central hypothesis that the defoliation dynamics during the period of occupation by animals in pastures formed by Brachiaria brizantha under rotational stocking varies among cultivars during the year. The experimental design used was randomized blocks with three treatments and three repetitions, with the cultivars consisting of Brachiaria brizantha cv. Xaraés, BRS Paiaguás, and Ecótipo B4. The defoliation patterns during the grazing periods were estimated using the marked tiller technique. Despite alterations in the tiller and forage mass components in the wet and dry seasons, no variations were observed in the tiller defoliation dynamics and the respective structural components. In the wet season, the area grazed only once was greater for BRS Paiaguás compared to the other two cultivars, but the other areas representing the grazing horizons were equally exploited among the grass varieties during the year. Therefore, based on the defoliation dynamics of pastures in Brazil’s tropical climate, it is possible to suggest that pastures formed by grasses with different structures and growth habits can be submitted to similar management strategies without impairing the forage canopy exploitation by the animals.

Defoliation Dynamics on Grazing Horizons in Pastures Intercropped by Panicum maximum, Brachiaria brizantha, and Brachiaria decumbens

“…The intercropped pasture was managed with 40% reduction of the forage canopy, it was verified that the grasses with the highest height (Figure 2A and 2B) allowed the greater depths of defoliation, and this event occurred as the horizons were being molded. This is an indication that animals adjust the depth of defoliation (Fernandes et al, 2020b), and begin to avoid structures of the tiller that have low nutritive value (Romera et al, 2012;Mezzalira et al, 2017), which may explain the proportionality of defoliation severity in pseudostem (Table 3 and Figure 3B).…”

“…With the reduction of the length of the tiller, it was verified that grazing horizons could occur (Fernandes et al, 2020b; Figure 1). Therefore, it was assumed that the horizons evaluated would be a source of variation that could modify the defoliation process, or even the preference among the cultivars intercropped.…”

“…From these measurements, the severity of defoliation (plant tissue removed at each touch) was quantified according to the following formula: severity (%)= [(initial length-final length) / initial length]. The frequency of defoliation was calculated from the following formula: frequency (%)= number of touches observed in each grass ÷ total number of marked tillers ÷ interval between horizon formation (Days) (Adapted from Fernandes et al, 2020b).…”

“…Representation of the molded horizon defoliation process (Adapted fromFernandes et al, 2020b). Representation of the molded horizon defoliation process (Adapted from…”

Aspects related to the forage potential of sorghum: Review

“…Atualmente, as pastagens cultivadas utilizadas que apresentam potencial forrageiro são as gramíneas dos gêneros Brachiaria e Panicum. Esses dois gêneros não são capazes de suprir a demanda de forragem ao longo do ano, pois sofrem com a escassez de chuva (Barbosa et al, 2007(Barbosa et al, , 2011Euclides et al, 2008;Fernandes et al, 2020). Além disso, as cultivares de Panicum são extremamente exigentes em fertilidade do solo, por isso torna-se necessário a associação e interação com novos matérias forrageiros para equilibrar a produção de forragem.…”