Forage Legumes in Tropical Regions: Recent Advances and Future Challenges

Nitrogen input in tropical pastures increases forage and animal productivity. Forage legumes can fix atmospheric nitrogen and are the most economical way to add this nutrient to the soil. Our objective was to report the benefits of forage legumes in tropical pastures and possible strategies to implement different forage legumes. In tropical conditions, such as in Brazil, the use of forage legumes is still scarce. Even with low legume adoption on tropical pastures, forage legumes can provide ecosystem services. Increased animal productivity is the first ecosystem service provided by these legumes, mainly due to the addition of nitrogen that is typically the most limiting nutrient on tropical soils and yet the most important driver of plant growth and development. Legumes also provide an opportunity to increase nitrogen cycling in grassland, reducing grassland degradation. Pastures that include legumes have greater litter quality than grass monocultures, increasing soil organic matter at a faster rate. Legumes improve diet nutritive value and animal performance, resulting in reduced enteric methane emissions per unit of animal product. Additionally, legumes are generally associated with lower nitrous oxide emissions than N-fertilized grass swards and reduce the carbon footprint from the system due to nitrogen manufacture, transport, storage, and application. However, the greatest challenge in tropical pastures is to increase the adoption of forage legumes. It is necessary to understand the role of different legumes in the pasture environment. Some legumes have high herbage accumulation and biological nitrogen fixation potential, but they have low canopy stability; nonetheless, they could be used on short-lived pastures as well as integrated crop-livestock systems. When the objective is to achieve grass-legume stability in mixed pastures, it is necessary to use clonal propagation legumes and provide appropriate defoliation management to minimize light competition among plant communities

Legume and Nitrogen Fertilization Affect Animal Performance and Enteric Methane Emission of Nellore Heifers

Methane emission from livestock operation is an important source of greenhouse gas and contributes to global warming. Forage legume secondary compounds may mitigate methane emissions by reducing methanogenic population in the rumen. This study evaluated animal performance and methane emission from beef cattle grazing either a mixed pasture [Brachiaria brizantha cv. Marandu (palisadegrass) and Arachis pintoi (forage peanut) cv. BRS Mandobi] or a palisadegrass monoculture with or without nitrogen (N) fertilisation. A 2.5-yr continuous stocking experiment was carried out in southeast Brazil, on a randomized complete block design with three treatments and four replicates. Two Nellore heifers were used as tester animals and additional put-and-takes were used to keep canopy height at 20-25 cm. The treatments comprised three pasture types: 1) palisadegrass-forage peanut mixed pasture (GRASS+LEGUME); 2) palisadegrass + 150 kg N/ha/year (GRASS+N); 3) palisadegrass without N fertilization (GRASS). Response variables included average daily gain (ADG), forage intake, and methane emission. Methane emission was estimated by the sulphur hexafluoride (SF6) tracer technique. There was no difference between grazing systems for the ADG (P = 0.439) and DMI (P = 0.394; averages of 0.433 kg/d and 2.10 %BW/d, respectively). In the GRASS+LEGUME, there was a decrease of 11.7% in methane emission per animal (148 vs. 170 and 165 g/day for GRASS+N and GRASS, respectively; P = 0.001). Grazing systems including legume reduced methane emission per unit of ADG (365 vs. 428 and 398 g/kg for GRASS and GRASS+N, respectively; P = 0.061) and per carcass gain (656 vs. 800 g of methane/kg carcass for GRASS; P = 0.022). Intake of condensed tannins was greater for GRASS+LEGUME (0.61 vs. 0.17 %BW/d, P \u3c 0.001). Forage peanut decreased enteric methane emission intensity, reducing carbon footprint of livestock systems in Southeast Brazil

How Does N Fertilization or Forage Legumes Affect Forage and Animal Production?

Livestock grazing in tropical climates is characterized by low productivity. Forage and animal production can be improved by applying nitrogen (N) fertiliser or using forage legumes. This 2.5-yr study assessed the canopy structure and productivity of beef cattle grazing either a mixed pasture of Brachiaria brizantha cv. Marandu (palisadegrass) and Arachis pintoi (forage peanut) cv. BRS Mandobi or a Marandu palisade grass monoculture with or without N fertilisation. The experiment was carried out in Southeast Brazil, where the canopy structure (herbage mass) and animal productivity (stocking rate and liveweight gain per ha) were compared for three types of pastures: 1) mixed pasture of Marandu palisade grass and forage peanut (GRASS+LEGUME); 2) a monoculture of Marandu palisadegrass fertilised with 150 kg N/ha/year (GRASS+N); and 3) monoculture of Marandu palisadegrass without N application (GRASS), under continuous stocking. A minimum of two Nellore heifers and additional put-and-takes were used to keep canopy height at 20-25 cm. A randomized complete block design was used with four replicates; seasons were considered repeated measurements over time. Herbage mass was greater in the GRASS+N pasture (P \u3c 0.001); however, in the last three seasons (Spring II, Summer III, and Fall III), there was no difference to GRASS+LEGUME pasture. In the GRASS+LEGUME pasture, there was an increase of legume mass (1.260 to 2.565 kg/ha) and botanical composition (23.6 to 39.1% of legume in forage mass) throughout the study. The stocking rate (P \u3c 0.001) and liveweight gain per ha (P \u3c 0.001) were greater in GRASS+N, without difference among GRASS+LEGUME and GRASS pastures in the first seven seasons. In the last three seasons, with an increase of legume proportion, stocking rate and liveweight were intermediate for GRASS+LEGUME pasture. Legume increased herbage mass and animal productivity in the long term. Immediate responses were achieved with N fertilization

Short-Term Soil Organic Matter and Carbon Responses to Contrasting Grazing Intensities in Integrated Crop-Livestock Systems

Combining integrated crop-livestock systems under no-till management may improve soil organic matter (SOM) build up and improve soil C sequestration. Grazing cover crops appears as a possibility to combine crops and livestock in a farm system. Further SOM and soil C increase can be achieved by adding perennial grasses into crop rotations. However, the effect of grazing intensity in such systems are not fully understood. This 2-yr study investigated short-term effects of cropping system [winter cover crops-summer cotton (Gossypium hirsutum L.) and winter cover crops-summer bahiagrass (Paspalum notatum Flüggé) rotations], grazing intensity (no grazing, heavy, moderate, and light grazing), and N fertilization (34 and 90 kg N ha-1 ), on OM and soil C of the soil-surface (0-15 cm) and deep-soil (0-90 cm) under no-till. Preliminary results indicate that treatments containing bahiagrass improved SOM in 1.5 g kg-1 compared to winter grazing on cover crops-cotton systems (P = 0.017). There were no differences among treatments for soil total C stock (15.4 Mg ha-1) and particulate OM-C (4.8 Mg ha-1) at the 15-cm depth (P \u3e 0.1). Carbon concentration increased from 8.0 to 12.6 g kg-1 as aggregate fraction decreased from 250 – 2000 to \u3c 53 µm (P \u3c 0.001). Nonetheless, C stock was not affected by aggregate fraction, with each fraction containing 3.8 Mg C ha-1, on average. Carbon stocks from 0-15, 15-30, 30-60, and 60-90-cm depths did not differ among treatments (P = 0.743), totalizing 30.4 Mg C ha-1 in the soil profile. Long-term studies are necessary to better understand the role of cropping system and grazing intensities on soil OM and C responses on surface and deep soil

Anharmonic transitions in nearly dry L-cysteine I

Two special dynamical transitions of universal character have been recently observed in macromolecules at $T_{D}\sim 180 - 220$ K and $T^{*}\sim 100$ K. Despite their relevance, a complete understanding of the nature of these transitions and their consequences for the bio-activity of the macromolecule is still lacking. Our results and analysis concerning the temperature dependence of structural, vibrational and thermodynamical properties of the orthorhombic polymorph of the amino acid L-cysteine (at a hydration level of 3.5%) indicated that the two referred temperatures define the triggering of very simple and specific events that govern all the biochemical interactions of the biomolecule: activation of rigid rotors ($T<T^{*}$), phonon-phonon interactions with phonons of water dimer ($T^{*}<T<T_{D}$), and water rotational barriers surpassing ($T>T_{D}$).Comment: 4 pages, 4 figures, submitted to Physical Review Letter

Diamide insecticide resistance in transgenic Drosophila and Sf9-cells expressing a full-length diamondback moth ryanodine receptor carrying an I4790M mutation

BACKGROUNDResistance to diamide insecticides in Lepidoptera is known to be caused primarily by amino acid changes on the ryanodine receptor (RyR). Recently, two new target site mutations, G4946V and I4790M, have emerged in populations of diamondback moth, Plutella xylostella, as well as in other lepidopteran species, and both mutations have been shown empirically to decrease diamide efficacy. Here, we quantify the impact of the I4790M mutation on diamide activation of the receptor, as compared to alterations at the G4946 locus.RESULTSI4790M when introduced into P. xylostella RyR expressed in an insect-derived Sf9 cell line was found to mediate just a ten-fold reduction in chlorantraniliprole efficacy (compared to 104- and 146-fold reductions for the G4946E and G4946V variants, respectively), whilst in the field its presence is associated with a ≥150-fold reduction. I4790M-mediated resistance to flubendiamide was estimated to be >24-fold. When the entire coding sequence of P. xylostella RyR was integrated into Drosophila melanogaster, the I4790M variant conferred ~4.4-fold resistance to chlorantraniliprole and 22-fold resistance to flubendiamide in the 3rd instar larvae, confirming that it imparts only a moderate level of resistance to diamide insecticides. Although the I4790M substitution appears to bear no fitness costs in terms of the flies' reproductive capacity, when assessed in a noncompetitive environment, it does, however, have potentially major impacts on mobility at both the larval and adult stages.CONCLUSIONSI4790M imparts only a moderate level of resistance to diamide insecticides and potentially confers significant fitness costs to the insect

Desempenho de novilhas em pastagens formadas pelos capins tifton 85, xaraés e mombaça, sob lotação rotativa.

O experimento foi conduzido na Estação de Zootecnia do Extremo Sul (Essul), pertencente a Comissão Executiva do Plano da Lavoura Cacaueira (CEPLAC), localizada no município de Itabela - Bahia - Brasil. Com o objetivo de avaliar o ganho de peso individual e por unidade de área de novilhas girolandas manejadas sob lotação rotativa em três pastagens fertilizadas com nitrogênio e irrigadas. As pastagens foram de Tifton 85, com 18 piquetes de 667 m2 , Xaraés e Mombaça, ambos com 28 piquetes de 429 m2 . O delineamento experimental foi em blocos casualizados com medidas repetidas no tempo ou por ciclo de pastejo. Com base em 224 dias de avaliações, não foram observadas diferenças significativas quanto ao ganho de peso por animal, por área e nem na lotação animal, ficando os ganhos por unidade de área entre 2,59 e 3,52 kg ha -1 dia-1 e a lotação entre 5,06 e 5,61 UA ha-1

Unravelling the molecular determinants of bee sensitivity to neonicotinoid insecticides

This is the final version of the article. Available from the publisher via the DOI in this record.The impact of neonicotinoid insecticides on the health of bee pollinators is a topic of intensive research and considerable current debate [1]. As insecticides, certain neonicotinoids, i.e., N-nitroguanidine compounds such as imidacloprid and thiamethoxam, are as intrinsically toxic to bees as to the insect pests they target. However, this is not the case for all neonicotinoids, with honeybees orders of magnitude less sensitive to N-cyanoamidine compounds such as thiacloprid [2]. Although previous work has suggested that this is due to rapid metabolism of these compounds [2, 3, 4, 5], the specific gene(s) or enzyme(s) involved remain unknown. Here, we show that the sensitivity of the two most economically important bee species to neonicotinoids is determined by cytochrome P450s of the CYP9Q subfamily. Radioligand binding and inhibitor assays showed that variation in honeybee sensitivity to N-nitroguanidine and N-cyanoamidine neonicotinoids does not reside in differences in their affinity for the receptor but rather in divergent metabolism by P450s. Functional expression of the entire CYP3 clade of P450s from honeybees identified a single P450, CYP9Q3, that metabolizes thiacloprid with high efficiency but has little activity against imidacloprid. We demonstrate that bumble bees also exhibit profound differences in their sensitivity to different neonicotinoids, and we identify CYP9Q4 as a functional ortholog of honeybee CYP9Q3 and a key metabolic determinant of neonicotinoid sensitivity in this species. Our results demonstrate that bee pollinators are equipped with biochemical defense systems that define their sensitivity to insecticides and this knowledge can be leveraged to safeguard bee health.his study received funding from Bayer AG. C.B. received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 646625 ). C.B. and K.B. received funding from Biotechnology and Biological Sciences Research Council (BBSRC, award number 15076182 ). The work at Rothamsted forms part of the Smart Crop Protection (SCP) strategic programme ( BBS/OS/CP/000001 ) funded through the Biotechnology and Biological Sciences Research Council’s Industrial Strategy Challenge Fund

Stoloniferous Forage Legumes for Sustainable Mixed Pastures in the Tropics

Brazil has over 80 million ha of tropical pastures formed with species of Brachiaria (syn. Urochloa), mostly grazed by beef cattle and with low fertilizer inputs, especially nitrogen. Recent investigations by our team show that stoloniferous legumes such as forage peanut (Arachis pintoi) and Desmodium ovalifolium are able to persist in mixed swards with Brachiaria brizantha (cv. Marandu) if grazing height is regulated (maximum 30 cm) so that radiation can reach the soil surface allowing stolons to take root. These legumes can persist in mixed pastures and produce milk or animal weight gains similar to the application of 120 to 150 kg N/ha/yr. In studies at the CEPLAC field station south Bahia State (16°39´S, 39°30´ W), N2O emissions from urine of dairy cattle were 0.47 and 0.76 kg N-N2O/ha/yr for a mixed forage peanut/Marandu pasture and Marandu monoculture + 120 kg N fertilizer ha/yr, respectively, equivalent to emission factors (EF) of 0.81 and 2.09%. N2O emissions from the N fertilizer were 2.70 and 0.24 kg N-N2O/ha (EFs of 4.10 and 0.40 %) for the two applications, respectively. N2O emissions from urine of beef cattle were 0.314 and 0.267 kg N-N2O/ha/yr for a mixed Desmodium ovalifolium/Marandu pasture and Marandu monoculture + 150 kg N fertilizer ha/yr, respectively, equivalent to EFs of 0.45 and 0.40 %. Annual N2O emissions from 3 x 50 kg N fertilizer were 0.30 kg/ha/yr. Preliminary results indicate that enteric methane emissions from cattle grazing a mixed forage peanut/Marandu pasture were 9 % lower per kg weight gain than those on an N-fertilized Marandu monoculture. Considering the total elimination of the fossil CO2 emissions associated with manufacture and application of N fertilizer, the substitution of 150 kg N by the mixed grass legume pastures represents a decrease in GHG emission intensity of over 20 %