It is well reported in the scientific literature that pastures can have similar net forage accumulation when managed with contrasting structures. However, we hypothesized that the dynamics of forage ...accumulation in grazed swards is linked to seasonal‐environmental conditions. Marandu palisadegrass (Brachiaria brizantha Hochst. ex A. Rich. was used as the forage species model. The experimental treatments were four grazing heights (10, 20, 30 and 40 cm) allocated to experimental units according to a randomized complete block design with four replicates and evaluated throughout four contrasting environmental seasons (summer, autumn, winter–early spring and late spring). Under rainy and warm periods, greater net forage accumulation was observed in pastures maintained taller; on the contrary, during the mild and dry periods, net forage accumulation rate reduced as grazing height increased. Such patterns of responses were related to compensations between tiller population density and tissues flows during summer and late spring and the reduced capacity of taller canopies to compensate lower population with greater growth rates during autumn and winter–early spring. Grazed swards changed their patterns of forage growth as they transitioned from favourable to more abiotic stressful conditions, suggesting that seasonal adjustments in grazing intensities are necessary in order to maximize forage production.
Abstract
Andropogon lateralis
is a tall and highly plastic tussock-forming grass native from southern South America. It is a frequent component of Campos and Subtropical highland grasslands that ...often becomes dominant under lax grazing regimes. The aim of this work was to analyze the response of species diversity and forage production of a natural grassland dominated by
A. lateralis
to a wide range of grazing intensity. We hypothesized that species diversity and forage production would both peak at the intermediate canopy heights determined by grazing regimes of moderate intensity. A grazing experiment was conducted in a highland grassland with mesothermal humid climate at 922 masl (Atlantic Forest biome, Santa Catarina state, Brazil) that comprised 87 species from 20 families but had 50% of its standing biomass accounted by
A. lateralis
. Four pre-/post-grazing canopy heights—12/7, 20/12, 28/17, and 36/22 cm (measured on
A. lateralis
)—were arranged in a complete randomized block design with four replications, and intermittently stocked with beef heifers from October 2015 to October 2017.
Andropogon lateralis
cover decreased (from 75 to 50%), and species richness increased (15–25 species m
−2
) as canopy height decreased. Grazing intensity did not affect annual forage production (4.2 Mg DM ha
−1
). This natural grassland dominated by
A. lateralis
had a high capacity to adjust to grazing regimes of contrasting intensity, maintaining forage production stable over a wide range of canopy heights. However, to prevent losses in floristic diversity, such grassland should not be grazed at canopy heights higher than 28 cm.
Grass species can be classified into different functional types based on their growth strategies, and contrasting persistence strategies are observed in different grass species. Excluding seedling ...recruitments, changes in populations of grasses are basically a trade-off between natality and mortality of tillers. We hypothesised that the persistence pathway of perennial grasses is linked to their growth strategy, regardless whether they are growing as monoculture or as a mixture. Species with contrasting growth strategies (Arrhenatherum elatius L., Dactylis glomerata L., and Festuca arundinacea Schreb.) were cultivated as monocultures and as a mixture and their tiller natality and mortality were evaluated for two years after swards establishment. All pastures maintained their population size during the experimental period, although decreases in tiller densities occurred during the warmer season. Arrhenatherum elatius had the highest tiller mortality and natality whereas the F. arundinacea had the lowest ones. Arrhenatherum elatius had many tillers appearing in all seasons but their tillers were short-lived. Conversely, F. arundinacea and D. glomerata developed numerous tillers during autumn and winter and their tillers survived, on average, almost six and three times longer than those of A. elatius, respectively. There were no differences in tillering dynamics among populations grown in monocultures or in the mixture. Regardless of whether they were cultivated in monocultures or as a mixture, the persistence pathway of perennial grasses is linked with their growth strategies with exploitative species presenting a high tiller turnover throughout the year whereas the persistence of more conservative species is based on a high tiller survival.
Grazing management has been the focus of the research with forage plants in Brazil for many years. Only in the last two decades, however, significant changes and advances have occurred regarding the ...understanding of the key factors and processes that determine adequate use of tropical forage plants in pastures. The objective of this review is to provide an historical overview of the research with forage plants and grasslands in Brazil, highlighting advances, trends, and results, as well as to describe the current state of the art and identify future perspectives and challenges. The information is presented in a systematic manner, favoring an integrated view of the different trends and research philosophies. A critical appraisal is given of the need for revision and change of paradigms as a means of improving and consolidating the knowledge on animal production from pastures. Such analysis idealizes efficient, sound and sustainable grazing management practices necessary to realize the existing potential for animal production in the tropics.
Molecular docking is a computational method widely used in drug discovery. Due to the inherent inaccuracies of molecular docking, visual inspection of binding modes is a crucial routine in the ...decision making process of computational medicinal chemists. Despite its apparent importance for medicinal chemistry projects, guidelines for the visual docking pose assessment have been hardly discussed in the literature. Here, we review the medicinal chemistry literature with the aim of identifying consistent principles for visual inspection, highlighting cases of its successful application, and discussing its limitations. In this context, we conducted a survey reaching experts in both academia and the pharmaceutical industry, which also included a challenge to distinguish native from incorrect poses. We were able to collect 93 expert opinions that offer valuable insights into visually supported decision-making processes. This perspective shall motivate discussions among experienced computational medicinal chemists and guide young scientists new to the field to stratify their compounds.
The diversity of traits plays a key role in the maximization of ecosystems' multi‐functionality, but interspecific competition in defoliated swards can lead to unpredictable changes in the functional ...traits over the plant community. However, we hypothesize that interrupting canopy regrowth at a height corresponding to critical leaf area index (LAI), associated with moderate intensity of defoliation, can be an effective management to preserve the functional traits of contrasting growth strategy grasses cultivated as a mixture. A 2‐year experiment was conceived to assess continuously several traits of three cool‐season perennial grasses (Arrhenatherum elatius exploitative, Dactylis glomerata moderately exploitative and Festuca arundinacea conservative) cultivated as single species stand or as a mixture. Dactylis glomerata was the less productive stand but no difference was observed between the mixture and the most productive monocultures. No change was observed in functional traits, whether the species were cultivated as monoculture or as a mixture. The dissimilarities over traits and, therefore, the functional identity of contrasting growth strategy grasses growing in multi‐specific swards was preserved when canopy regrowth was interrupted at a height corresponding to the critical LAI associated with moderate intensity of defoliation. Since the diversity of traits maximizes ecosystem multi‐functionality, our findings provide a step forward towards designing management practices that enhance ecosystems services delivered by cultivated multi‐specific grasslands.
Grasslands are global resources that provide multiple ecosystem services. There is a close relationship between diversity of traits and multi‐functionality. Attenuating stress and disturbance can preserve plants traits dissimilarities.
Cytochrome P450 2D6 (CYP2D6) is an enzyme that is involved in the metabolism of roughly 25% of all marketed drugs and therefore belongs to the most important enzymes in drug metabolism. CYP2D6 ...features a high degree of genetic polymorphism that can significantly affect the metabolic activity of an individual. In extreme cases, structural changes at the level of single amino acids can either increase its enzymatic activity abolishing the drug therapeutic effect or completely disable the enzyme and elevate drug plasma level potentially leading to adverse effects. In this study, starting from the crystal structure, we built a full-length membrane-anchored all-atom model of the wild-type CYP2D6 as well as five of its variants differing in the enzymatic activity. We validated our models with available experimental data and compared their structural properties with molecular dynamics simulations. The main focus of this study was to identify differences that could mechanistically explain the altered activity of the variants and improve our understanding of their functioning. We observed differences in the opening frequencies and minimal diameters of tunnels that connect the buried active site to the surrounding solvent environment. The variants CYP2D6*4 and CYP2D6*10 associated with missing or decreased activity showed less frequent opening of the tunnels compared to the wild-type. Both CYP2D6*10 and CYP2D6*17 showed a deprivation of an important ligand tunnel suggesting a feasible reason for their altered substrate specificity. Next, the altered fold at the N-terminal anchor region and the decreased active site volume caused by the amino acid mutations of the CYP2D6*4 variant offer an explanation for the absence of its metabolic activity. The mutations in CYP2D6*53 contributed to a significant enlargement of an important ligand tunnel and an extension of the active site cavity. This could explain the altered metabolic profile as well as the enhanced metabolic rates of this particular variant supporting its designation as a possible cause for the ultrarapid metabolizer phenotype. We believe these novel structural insights could advance the fields of personalized medicine and enzyme engineering. Furthermore, they could aid in guiding laboratory as well as computational experiments in the future.
This study evaluated the leaf area index (LAI) recovery mechanisms and forage accumulation rates on the regrowth of different grass species subjected to different defoliation intensities. For that ...purpose, plots of Pennisetum clandestinum (kikuyugrass), Lolium multiflorum (annual ryegrass), and Avena strigosa (black oats) were defoliated from 20 to 80 % of their initial heights (25, 20, and 25 cm, respectively). At different increments in height, forage samples were collected to ground level and used to estimate tiller population density (TPD), leaf area per tiller (LA), and forage mass. From these data, we calculated the leaf area index (LAI), average leaf area index (aLAI), and average and instantaneous forage accumulation rate (FAR and IFAR, respectively). Data were plotted over time (days) to describe LAI recovery and forage accumulation rates. As the defoliation intensity increased, greater canopy heights were needed for pastures to achieve their maximum forage accumulation rates, which required longer regrowth intervals. The need for high tiller recruitment after defoliation, which delayed canopy LAI recovery, seemed to be one of the main cause. Thus, grazing management strategies that involve costly tiller recruitment could decrease both overall forage production and sward persistence over time. However, the plant ability to recover LAI after successive intense defoliations seems to be species-dependent and related to their phenotypic plasticity.
A two‐year experiment assessed herbage production and above‐ and below‐ground characteristics of a highly productive monoculture (‘BRS Zuri’ guineagrass Panicum maximum Jacq.) and two mixtures of ...three grasses (Mixture 1: ‘BRS Zuri’ guineagrass, ‘BRS Xaraés’ palisadegrass Brachiaria brizantha Stapf., and ‘Basilisk’ signalgrass Brachiaria decumbens Stapf.; Mixture 2: ‘BRS Quênia’ guineagrass Panicum maximum Jacq., ‘Marandu’ palisadegrass Brachiaria brizantha Stapf., and ‘BRS Paiaguás’ palisadegrass Brachiaria brizantha Stapf.), cultivated in the Brazilian tropical savanna. Mixtures 1 and 2 were subjected to two grazing intensities (removal of 40 or 60% of pre‐grazing height) and ‘BRS Zuri’ guineagrass monoculture was defoliated to a single grazing intensity of 50%. Treatments were randomly assigned to fifteen 0.25‐ha plots and managed under intermittent stocking by cattle. Herbage accumulation rate was similar among pastures and years (p > .1). The root mass in the tussocks did not differ (p > .1), with mean values ranging between 0.62 to 1.81 kg DM m−2. Root density in the tussock interspaces was greater in the mixtures (p < .001), regardless of seasons (p = .405) and years (p = .292). The mixtures were dominated by guineagrass (70%) and palisadegrass (30%) at the end of the experiment, with the population of ‘Basilisk’ and ‘BRS Paiaguás’ being completely suppressed throughout the experimental period. Mixing guineagrass and brachiariagrasses can be an alternative to the traditional pastoral systems in the tropics, as it does not compromise herbage production and presents a capacity to produce more roots than a very productive monoculture of ‘BRS Zuri’ guineagrass.
Natural grasslands in southern Brazil are ecosystems that are naturally adapted to grazing. Despite the productivity and ecological relevance of these ecosystems, the effects of grazing intensity on ...their soil quality are still underexplored. This work aimed to determine whether increasing the grazing intensity would jeopardize the soil structure in a natural highland grassland in southern Brazil. Pastures were evaluated at four pregrazing canopy heights, 0.12, 0.20, 0.28 and 0.36 m, with Andropogon lateralis Nees as the reference species, and in one ungrazed control area. The pastures were intermittently stocked, and the postgrazing heights corresponded to 60% of the pregrazing targets (i.e., the postgrazing heights were 0.072, 0.12, 0.168 and 0.216 m). The experiment started in 2015 and was conducted for three years, with evaluations of soil physical properties performed in the final year. Forage growth and grazing were concentrated from October to May; during the winter, no grazing occurred for a period of approximately 4 months. The soil structure was evaluated at two points: after the end of the 2017/2018 grazing season, in June, and after the winter period, in October. Regardless of the canopy height, the presence of grazing animals increased the degree of compaction at the soil surface (0.0–0.05 m) to an intermediate level immediately after grazing, did not disaggregate the soil or change its carbon and nitrogen stocks, and increased soil macroporosity and water infiltration compared to those in the exclusion area (control). Increasing the grazing intensity (i.e., increasing the grazing frequency, corresponding to lower pregrazing canopy heights) increased the soil macroporosity and water infiltration rate, decreased the soil moisture and increased the soil penetration resistance. Except at the 0.12 m canopy height, the exclusion of grazing for 4 months allowed the soil water infiltration in the grazed plots to return to a level similar to that in the exclusion area. We conclude that there are a wide range of grazing intensities (corresponding to canopy heights of 0.12–0.36 m) that do not jeopardize the soil structural quality in highland grasslands. Furthermore, it was not possible to determine whether canopy heights below 0.12 m would disrupt the synergism at the soil-plant-animal interface in these natural ecosystems.
•Natural grasslands are global resources that have been threatened by human activity.•We assessed the effects of cattle grazing on soil structure in highland grasslands.•The soil water infiltration rate increased in grazed compared to ungrazed areas.•The soil structure was not jeopardized across a wide range of grazing intensities.
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