Forage mass and morphological composition of Marandu palisade grass pasture under rest periods

Abstract

An evaluation of productive potential is not the only factor used to determine grazing management efficiency; it is also necessary to know the structural characteristics of the canopy. The objective of this study was to evaluate the effects of two management styles on Marandu palisade grass pastures under rotational stocking with respect to the herbage mass, morphological composition, and structural characteristics of the pasture. The treatments under consideration were a) a fixed rest period of 30 days (RP30) or b) a rest period based on the time necessary for the canopy to reach 95% light interception (LI95). The experimental design was a completely randomized block with two blocks and three replicates within the blocks. Animals were placed in the paddocks when the grass reached the established management criteria, which were maintained for three days to reach 25 cm in stubble height. Shorter grazing intervals (22.8 vs. 30 days), lower pre-grazing heights (35.9 vs. 42.3 cm), and lower forage masses (4,411 vs. 5,290 kg/ha.cycle) were observed in LI95 pastures. The LI95 treatment had a higher leaf percentage (48.3 vs. 41.1) and the lowest percentage of dead forage (19.0 vs. 25.4) in the pre-grazing forage mass of the pasture in relation to that of RP30. Performing pasture management based on RP30 throughout the season is harmful to the pasture structure because it reduces the leaf percentage and increases the stem and senescent material in the available forage. The lower pre-grazing forage mass observed under LI95 management is offset by more grazing cycles within the rainy season.Index terms: Pre-grazing height; Grazing cycle; interception of photosynthetically active radiation; leaf mass. RESUMOA avaliação do potencial produtivo do pasto não é o único fator que pode ser usado para determinar a eficiência de manejo do pastejo, também é necessário considerar as características estruturais do dossel. Neste estudo, objetivou-se avaliar a influência de dois critérios para definição do período de descanso do pasto de capim-marandu sobre a massa de forragem, a composição morfológica e as características estruturais do pasto durante a estação chuvosa. Os períodos de descanso estudados foram: fixo de 30 dias (PD30) e variável, conforme a interceptação de 95% da radiação fotossinteticamente ativa (IL95). O delineamento experimental utilizado foi em blocos inteiramente casualizados, com duas repetições de área e três repetições dentro de bloco. Os animais (vacas mestiças) foram colocados nos piquetes, logo que os pastos atingiam os critérios de manejo estabelecidos e permaneciam dentro dos mesmos durante três dias, de forma a atingir a altura de resíduo de 20-25 cm. Menor intervalo entre pastejo (22,8 vs. 30 dias), menor altura pré-pastejo (35,9 vs. 42,3 cm) e menor massa de forragem verde (4.411 vs. 5.290 kg/ha.ciclo) foram observados no pasto sob IL95. Contudo, o pasto sob IL95 apresentou maior percentual de lâmina foliar (48,3 vs. 41,1) e menor percentual de material morto (19,0 vs. 25,4) na massa de forragem ...

Fixed versus variable rest period effects on herbage accumulation and canopy structure of grazed 'Tifton 85' and 'Jiggs' Bermuda grass

“…Differences for grass growth under grazing can contribute to differences of postgrazing canopy characteristics. Differently from the result obtained in the present study, Anjos et al (2016) reported an increase of grazing cycles, when a variable rest (95% LI) period was used on 'Marandu' palisade grass [Urochloa brizantha (A. Rich.…”

Effect of nitrogen application rate on yield, forage quality, and animal performance in a tropical pasture

“…Nitrogen application rates affected green leaves (Table 1). The green leaf content was lower than that reported when Marandu grasses were fertilized with nitrogen in rotational grazing 21 , and in line with that measured in a Cerrado biome 22 . The stem + sheath proportion varied with the nitrogen application rate (P < 0.01) quadratically and averaged approximately 350 g kg −1 DM (Table 1), being in line with the average value reported in Mata Atlantica 23 and a similar ecosystem 24 .…”

Milk fatty acid profile of Holstein x Gyr cows on 'Marandu' grass pasture under different grazing strategies

“…For the variable rest period, cows entered the paddocks whenever the pasture reached 95% canopy-light interception -estimated by a canopy analyzer AccuPAR Linear PAR/LAI Ceptometer, model LP-80 (Decagon Devices Inc., Pullman, WA, USA); for the fixed rest period, the pasture was managed to allow 30 days of rest. It should be noted that this experimental area had previously been managed using these treatments since October 2010 (Anjos et al, 2016).…”

“…In Brazil, systems of rotational grazing under intermittent stocking, based on the use of fixed or variable pasture rest periods, have been studied. In pastures of U. brizantha 'Marandu', Madeiro (2014) and Anjos et al (2016) compared the morphological and chemical compositions of pastures managed under fixed 30-day rest periods with variable rest periods, based on the interception of 95% of the photosynthetically active radiation. These authors observed a greater leaf proportion, a lower proportion of senescent material and, therefore, a higher nutritional value in pastures managed under variable rest periods.…”