Producción animal en pasturas de tres leguminosas asociadas con Urochloa decumbens en los Llanos Orientales de Colombia

In a loamy clay soil of the Colombian Altillanura, animal production of the legumes Centrosema molle accession CIAT 15160, C. macrocarpum accession CIAT 15799 and Grona heterocarpa subsp. ovalifolia (syn. Desmodium ovalifolium) cv. Maquenque, in association with Urochloa decumbens (syn. Brachiaria decumbens) cv. Decumbens, was evaluated under rotational grazing with zebu Brahman steers. The experiment was established in a native savanna area at the Carimagua Research Center of Agrosavia, in a randomized complete block design with three replications. During three years of grazing, C. molle stood out over the other legumes, due to its good forage production and ability to associate and persist with the grass, reaching 40% in the botanical composition in the first year and 24% in the third year. The highest animal liveweight (LW) gains were achieved with this legume with, on average, 760 g/animal/day in the rainy season and 500 g/animal/day in the dry season. With an average stocking rate equivalent to 800 kg LW/ha, mean annual hectare productivity of the pasture with C. molle reached 600 kg LW compared with an average of about 380 kg/ha/year obtained in the other associations and in the grass-only pasture. It is concluded that C. molle CIAT 15160 is a promising pasture legume for the region and confirming its productivity and persistence at farm level and in association with other grasses seems warranted.

Harvesting subterranean clover seed – current practices, technology and issues

Subterranean clover (Trifolium subterraneum L.) is Australia’s most widely sown annual pasture legume. Its widespread use as a pasture plant requires a well-functioning seed production industry, and Australia is the only significant producer of subterranean clover seed globally. However, the sustainability of this industry is under threat due to its reliance on ageing harvest equipment and the resultant environmental impacts. In order to evaluate seed harvesting practices, technology, and issues, we report on case studies, workshops, and a survey of seed producers across southern Australia. The Horwood Bagshaw Clover Harvester, designed in the 1950s, remains the most popular subterranean clover seed harvester. We discuss its use and modifications, and document several contemporary issues facing the seed production industry. Issues are primarily soil erosion and degradation; the expensive, slow and labour-intensive harvest process; and poor reliability and maintainability of harvesters that are now at least 30 years old. We conclude the root cause of these issues is the suction harvest technology utilised by the Horwood Bagshaw Clover Harvester. Analysis of the current harvest system is provided to support the development of new approaches to harvest subterranean clover seeds.

Exogenous ACC Deaminase Is Key to Improving the Performance of Pasture Legume-Rhizobial Symbioses in the Presence of a High Manganese Concentration

Manganese (Mn) toxicity is a very common soil stress around the world, which is responsible for low soil fertility. This manuscript evaluates the effect of the endophytic bacterium Pseudomonas sp. Q1 on different rhizobial-legume symbioses in the absence and presence of Mn toxicity. Three legume species, Cicer arietinum (chickpea), Trifolium subterraneum (subterranean clover), and Medicago polymorpha (burr medic) were used. To evaluate the role of 1-aminocyclopropane-1-carboxylate (ACC) deaminase produced by strain Q1 in these interactions, an ACC deaminase knockout mutant of this strain was constructed and used in those trials. The Q1 strain only promoted the symbiotic performance of Rhizobium leguminosarum bv. trifolii ATCC 14480T and Ensifer meliloti ATCC 9930T, leading to an increase of the growth of their hosts in both conditions. Notably, the acdS gene disruption of strain Q1 abolished the beneficial effect of this bacterium as well as causing this mutant strain to act deleteriously in those specific symbioses. This study suggests that the addition of non-rhizobia with functional ACC deaminase may be a strategy to improve the pasture legume–rhizobial symbioses, particularly when the use of rhizobial strains alone does not yield the expected results due to their difficulty in competing with native strains or in adapting to inhibitory soil conditions.

Clitoria ternatea (butterfly-pea).

C. ternatea is a pasture legume also commercialized as a garden ornamental that has been widely introduced in agroforestry systems in tropical and subtropical regions of the world. Traits such as its high growth-rates, drought tolerance and adaptation to heavy clay soils suggest that this species could be used to improve natural grasslands (Staples, 1992). However, these traits have also helped this species to escape from cultivation and become an invasive species in river banks, creek lines, the margins of waterholes, irrigation channels, disturbed sites, roadsides and disturbed open woodlands and grasslands in Australia, Hawaii, the Galapagos Islands, Fiji, and on many islands in the Pacific region (Smith, 1985; Wagner et al., 1999; PIER, 2016; Weeds of Australia, 2016). C. ternatea is an aggressive colonizer of disturbed sites and open areas with the capability to displace and completely outcompete native vegetation (Weeds of Australia, 2016). Past risk assessments have given it a score of 7 (reject) for Australia and 9 (high risk) for the Pacific (PIER, 2016).

Clearing confusion in Stylosanthes taxonomy. 2. S. macrocephala M.B. Ferreira & Sousa Costa vs. S. capitata Vogel and S. bracteata Vogel

Stylosanthes macrocephala was described as a new species in 1977 and has become an economically important pasture legume. It has recently been claimed to be conspecific with S. capitata, also an economically important species. This paper refutes this synonymization and summarizes morphological descriptions as well as genetic studies and cytological evidence indicating that diploid S. macrocephala should be considered a separate species, even being a likely progenitor of tetraploid S. capitata. Early confusion with S. bracteata is also discussed.

Metabolic Profiling Provides Unique Insights to Accumulation and Biosynthesis of Key Secondary Metabolites in Annual Pasture Legumes of Mediterranean Origin

Annual legumes from the Mediterranean region are receiving attention in Australia as alternatives to traditional pasture species. The current study employed novel metabolic profiling approaches to quantify key secondary metabolites including phytoestrogens to better understand their biosynthetic regulation in a range of field-grown annual pasture legumes. In addition, total polyphenol and proanthocyanidins were quantified using Folin–Ciocalteu and vanillin assays, respectively. Metabolic profiling coupled with biochemical assay results demonstrated marked differences in the abundance of coumestans, flavonoids, polyphenols, and proanthocyanidins in annual pasture legume species. Genetically related pasture legumes segregated similarly from a chemotaxonomic perspective. A strong and positive association was observed between the concentration of phytoestrogens and upregulation of the flavonoid biosynthetic pathway in annual pasture legumes. Our findings suggest that evolutionary differences in metabolic dynamics and biosynthetic regulation of secondary metabolites have logically occurred over time in various species of annual pasture legumes resulting in enhanced plant defense.

Vegetation change 10 years after cattle removal in a savanna landscape

Following the establishment of a conservation reserve, changes in ground stratum vegetation following removal of cattle were examined in a northern Australian savanna over a 10-year period. The floristic composition of 40 vegetation plots in lowland savannas were surveyed shortly after acquisition of the property, and then surveyed twice in the following 10 years after cattle removal. Some notable ecosystem-transforming introduced species (weeds) such as Themeda quadrivalvis remained relatively stable, whereas the pasture legume Stylosanthes scabra increased in cover. The species richness of both native and introduced plants increased. Various plant functional groups changed in relative cover, with a decline in relatively unpalatable grasses and a corresponding increase in palatable grasses, responses that are consistent with recovery from grazing pressure. Our results show that removal of cattle in highly disturbed savanna ecosystems can have both positive and negative results for native ground stratum vegetation in the first decade of recovery.

145 Eco-efficiency of Northeast U.S. grass-fed beef systems

Grass-fed beef systems (GFB) are one approach proposed to improve the sustainability of animal-sourced foods. Our objective was to estimate carbon (CF) and reactive nitrogen (NF) footprints and cost of production (COP) for northeastern U.S. GFB. A partial life cycle assessment was conducted using the Integrated Farm System Model (IFSM). Systems were characterized using surveys and interviews. Representative operations were simulated in IFSM by grouping farms with similar environments and forage management practices. Environments were defined using USDA Plant Hardiness Zones. Farms were categorized as feed sufficient (FS: produced all supplemental forage on-farm) or feed importing (FI; purchased all supplemental forage). Differences between zones and farm types were analyzed using Dunn’s test with a Bonferroni correction and the Kruskal-Wallis test, respectively. Warmer zones supported longer grazing seasons (P < 0.01), greater pasture legume content (P < 0.05), and denser stocking rates (P < 0.01), resulting in twice the market weight production per hectare compared with farms in cooler zones (P < 0.01). Grazing season length and pasture legume content were similar between farm types (P > 0.1). FI herds were half the size of FS herds (P < 0.01), used 37% more land per animal (P < 0.01), and had 10% lighter market weights with 52% lower market weight production per hectare (P < 0.05). CF, NF, and COP/animal were 1.1, 1.3, and 2.1-fold greater for FI farms, respectively. Zone differences in climate, soils, and pasture legume content affected footprints. In warmer zones where soils had greater clay content, N2O contributed a greater portion of CF and NF, and NO3 leaching was moderate. In the coolest zone with coarser soil, N2O contributed a small portion of CF and NF, with greater NO3 losses. Analyses suggest attention to nitrogen management, efficient resource utilization, and botanical composition might reduce CF and NF.