ABSTRACT. This study was conducted to evaluate management strategies in Mombaça grass pastures (Panicum maximum) under intermittent grazing subjected to different residual heights. A randomized-block design with two treatments (two post-grazing residual heights: 30 and 50 cm) and three replications was adopted. Pasture heights pre-and post-grazing, forage mass and accumulation, rest and occupation periods, pasture morphological components, milk yield and quality forage were evaluated. The data were submitted to analysis of variance and the means were compared by the F test at 5% probability. A longer grazing interval was observed in the treatments under the more severe grazing intensity. For forage mass postgrazing, larger production and higher percentage of leaves were found with the 50 cm residue, as well as higher crude protein contents and digestibility of leaves and stems and lower lignin and neutral detergent fiber contents. The residual height of 50 cm is recommended for the management of Mombaça grass pasture, as it provides greater milk yield per animal and a larger number of grazing cycles, ensuring better use of the area.Keywords: defoliation, grazing system, pasture.Produção de pastos de capim-mombaça submetidos a alturas de resíduo RESUMO. O experimento foi conduzido, objetivando-se avaliar estratégias de manejo em pastos de capim-mombaça (Panicum maximum) sob lotação intermitente, submetidos a diferentes alturas de resíduo. O delineamento utilizado foi em blocos casualizados, com dois tratamentos (duas diferentes alturas de resíduo pós-pastejo -30 e 50 cm) e três repetições. Foram avaliadas a altura do pasto no pré e no pós-pastejo, a massa e o acúmulo de forragem, os períodos de descanso, de ocupação, a produção dos componentes morfológicos do pasto, a produção de leite e a qualidade da forragem. Os dados foram submetidos à análise de variância e as médias foram comparadas pelo teste F a 5% de probabilidade. Para tratamentos com intensidade de pastejo mais severa, notou-se maior intervalo de pastejo. Encontrou-se maior acúmulo de forragem para pastos manejados com altura de 50 cm de resíduo de pastejo. Para massa de forragem no pós-pastejo, obteve-se maior produção e maior porcentagem de folhas para o resíduo de 50 cm, bem como maiores teores de PB e digestibilidade para folhas e colmos, e menores teores de lignina e FDN. Para manejo de pastos de capim-mombaça, recomenda-se a altura de 50 cm de resíduo, por promover maior produção de leite por animal e maior número de ciclos de pastejo, garantindo melhor aproveitamento da área.Palavras-chave: desfoliação, sistema de pastejo, pasto.

Forage accumulation (FA) is a key response in grazing experiments, and estimates of FA in continuously stocked pastures are often obtained using exclosure cages. This study evaluated how 14-, 21-, and 28-d exclusion periods using cages affected morphological, physiological, and morphogenetic responses of continuously stocked 'Mulato II' hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) pastures maintained at 20-and 30-cm canopy height and how this affected estimates of FA. Grazing exclusion resulted in greater rates of leaf elongation (LER; 1.62 vs. 1.37 cm tiller −1 d −1), stem elongation (SER; 0.16 vs. 0.07 cm tiller −1 d −1), leaf growth (101 vs. 86 kg dry matter [DM] ha −1 d −1), and stem growth (3.4 vs. 1.8 kg DM ha −1 d −1) inside the cages compared with outside. Greater LER resulted in greater final leaf length and leaf area index (LAI) in longer exclusion periods. With greater LAI, photosynthesis was greater within the exclosure cages than on pasture (54.5 vs. 43.9 μmol CO 2 m −2 s −1). Greater leaf growth rate, together with same tiller population density and leaf senescence rate (LSR) across exclusion periods, resulted in overestimated FA by 14, 26, and 24% for 14-, 21-, and 28-d exclusions, respectively. There was no effect of canopy height on FA, because greater LER and SER values in 30-cm canopies were compensated by greater LSR. Choice of sites for cage placement by visual appraisal and reduced number of sampling sites resulted on "negative" values of calculated FA for the 14-d exclusion, making the choice of sampling sites a major source of error in estimation of actual FA. Increasing the number of sampling sites and using indirect measurements of forage mass (FM) may increase the accuracy of FM and FA estimates.

Primeiramente, agradeço a Deus pelo dom da vida e aos bons espíritos pela forma com que me conduziram para chegar até aqui.

In experiments with selection of perennial plants, the initial performance is expected to be maintained throughout the productive life. The probability of repeating the agronomic response can be evaluated by the repeatability coefficient. The objective was to estimate repeatability coefficients of agronomic characteristics in Panicum maximum Jacq. using different methods and identify the best combinations between harvests according to the genotypic stabilization. Seventeen genotypes were evaluated in a randomized complete block design with three replicates. The coefficients of repeatability were estimated by the methods: ANOVA, structural analysis based on the mean of the correlation coefficients (SACOR), analysis of principal components based on the covariance matrix (PCCOV) and correlation matrix (PCCOR). In the genotypic stabilization, coefficients estimated by ANOVA and PCCOR were used. For total DM, repeatability coefficients ranged from 0.3500 to 0.4300 by the ANOVA and PCCOR methods, respectively. High repeatability coefficients were found for the characteristic leaf DM, while low coefficients were observed for leaf and stem percentages and leaf:stem ratio. For the genotypic stabilization of total DM and leaf:stem ratio, the best coefficients were observed for the combination of harvests 5 to 8. There are variations in the estimate of repeatability by different methods and the highest coefficients were those of the principal components based on the correlation and covariance matrices. For the genotypic stabilization, the best coefficients of repeatability and determination were observed for the harvests performed in the second rainy period.

For full list of author affiliations and declarations see end of paper Context. Defoliation management by grazing or clipping, combined with nitrogen (N) fertilisation, can increase forage production in tropical grasses. Use of pasture canopy height as a practical tool for

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Rotational stocking (RS) is generally associated with the intensification of pasture‐based animal production systems, although many studies have shown little advantage over continuous stocking (CS). The objective of this research was to describe and explain the effects of two average canopy heights (20 and 30 cm) and three stocking methods (CS; rotational stocking with lenient defoliation, RSL; and rotational stocking with moderate defoliation, RSM) on forage accumulation (FA), vertical distribution of plant‐part components, and nutritive value of ‘Mulato II’ hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) during two summer rainy seasons in Piracicaba, São Paulo, Brazil. Pastures were maintained at average canopy height of 20 and 30 cm under CS, and treatments under RSL and RSM were imposed by variations of ±20 and 30% of the average canopy heights, representing defoliation intensities of 33 and 47% of the pre‐graze heights, respectively. The FA was not affected by CS, RSL, RSM stocking methods, averaging 8090 kg DM ha−1 year−1. Canopy bulk density and distribution of plant‐part components in the canopy profile were better at the average canopy height of 20 cm, accompanied by the greater nutritive value. The leaf bulk density was generally greater in RSM compared to CS. Pastures under CS had greater crude protein and in vitro digestible matter, and lesser neutral detergent fibre concentrations. Mulato II brachiariagrass should be managed at an average height of 20 cm under CS.

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