Canopy Characteristics, Ingestive Behaviour and Herbage Intake in Cultivated Tropical Grasslands

Compared to temperate systems, there have been few detailed assessments of canopy characteristics and associated grazing behavior in planted tropical grasslands. Reasons include the large number of forage species used in warm climates, the diversity of their morphology, research priorities emphasizing germplasm evaluation and management, and limited resources. This review describes canopy attributes of C4 grass pastures, highlights the most important relationships between grazing behavior and these canopy characteristics, and discusses the implications of canopy characteristics and grazing behavior for long-term intake and animal performance. It is suggested that the largest differences in canopy characteristics between tropical and temperate swards are not total canopy measures but those of the upper canopy strata including leaf proportion and bulk density. This occurs because tropical swards, unlike many temperate ones, have large vertical heterogeneity in density, plant-part proportion and nutritive value. In temperate swards, bite weight is primarily a function of sward height, but leaf percentage, leaf mass, or green herbage mass of the upper strata of the canopy usually are more important with C4 grasses. The manner in which leaf is presented to the animal and the degree to which it can be prehended separate from stem and dead material of low digestibility are also of great significance in pastures based on C4 grasses

\u3ci\u3eAeschynomene\u3c/i\u3e and \u3ci\u3eCarpon Desmodium\u3c/i\u3e: Legumes for Bahiagrass Pasture in Florida

Soils and climate are very diverse across Florida, and no single legume has state-wide adaptation. However, aeschynomene (Aeschynomene americana), an annual, and carpon desmodium (Desmodium heterocarpon) cv. Florida, a perennial, are the most commonly used legumes for grazing on the central and southern peninsula, which produces 65% of Florida\u27s beef calves. Both grow well with bahiagrass (Paspalum notatum), which is the main pasture grass, with ~1M ha state-wide. Circa 65K ha of bahiagrass contain at least limited quantities of aeschynomene and 14K ha contain carpon desmodium

Climate Change and Legume Performance in Grassland Agroecosystems

We reviewed the literature to assess the effect of climate change factors on forage legumes. Whether growing in monoculture or mixtures with grasses, exposing legumes to elevated CO2 (eCO2) generally leads to sustained increases in forage accumulation (FA) and N fixation, but elevated temperature (eT) in conjunction with eCO2 usually reduces magnitude of these responses. In legumes, nodules represent large C sinks, precluding photosynthetic acclimation to eCO2 observed in non-N fixing plants. Greater N fixation in legume-grass mixtures exposed to eCO2 is due to greater percentage of legume N derived from symbiotic fixation and often an increase in legume proportion in mixtures. Herbage nutritive value (NV) responses to eCO2 are less pronounced than FA, but lesser herbage N and greater non-structural carbohydrate (NSC) concentrations are common with eCO2. Drought effects on legume NV are inconsistent, but eT usually decreases NV. Data from one legume species suggest eCO2 and eT negatively affect pollen grain morphology and viability, but they increase flower number and nectar sugar concentration. Under eT, flowers opened earlier in the day causing earlier pollinator visits, but when combined with water stress, eT reduced pollinator visits. Though there is variation in the literature for some responses, we conclude that eCO2 generally increases legume FA, N fixation, and tissue NSC concentration, while reducing herbage N concentration. Drought reduces FA, but drought effects on NV are not consistent. Elevated temperature has a negative effect on legume NV, and, when combined with eCO2, can reduce the magnitude of the positive FA and N fixation response to eCO2. Climate change factors can affect legume pollen viability and pollinator behavior, potentially influencing plant reproductive success. Overall, effects of climate change factors on forage legumes can be generalized, but interactions among change factors and site-specific soil and climate conditions may cause variation from expected responses

Impact of Overseeding Cool-Season Annual Forages on Spring Regrowth of Tifton 85 Bermudagrass

Field observations have shown stand reduction and slow spring regrowth of Tifton 85 bermudagrass (Cynodon spp.) pastures overseeded with temperate forages for grazing during the cool season. This experiment compared the effect of cool-season management programs, including overseeding and use of different grazing treatments, on productivity of Tifton 85 the following warm season. There were seven treatments: four were bermudagrass overseeded with a cool-season annual forage mixture (two grasses and two legumes) and grazed differentially, and three were bermudagrass controls with differences in amount of residual stubble remaining at beginning of autumn. There was only a slight delay in initiation of Tifton 85 spring regrowth relative to the unseeded controls and no apparent stand loss resulting from overseeding coolseason forages. Late spring and summer Tifton 85 production generally was greater on seeded than non-seeded areas, possibly resulting from the nitrogen (N) release from decaying coolseason legumes. Grazing management of winter species in seeded plots and stubble height of bermudagrass in control plots had no effect on bermudagrass performance. Nutritive value responses generally favored overseeded plots. These data, though from one year, show no negative effect on Tifton 85 bermudagrass performance from overseeding and grazing coolseason annual forages during winter

Sustainable Intensification of Livestock Systems Using Forage Legumes

Global human population is increasing and expected to reach 9.7 billion people by 2050. Sustainable intensification (SI) of agricultural systems is key to increase food production while minimizing impact on global natural resources. Forage legumes provide a myriad of ecosystem services (ES) and represent an important tool for promoting SI in livestock systems. Forage legumes associate with soil microorganisms to reduce atmospheric N2. This N input represents a valuable contribution to increase net primary productivity with reduced C footprint. In addition, forage nutritive value generally increases, resulting in greater animal performance. When forage legumes are integrated into livestock systems, they complement the essential role of grasses by adding N to the system, improving forage quality, sharing resources with the companion grass, and enhancing soil organic matter. Soil C:N ratio is typically in a narrow range; therefore, input of N is essential to increase C sequestration and maintain the soil C:N ratio. Additional ES provided by forage legumes include enhanced efficiency of nutrient cycling, improved pollinator habitat, medicine/food for humans, timber, wildlife habitat, and shade for livestock (tree legumes). There are options of herbaceous and arboreal legumes, as well as annuals and perennials. In temperate regions, herbaceous legumes are used widely (e.g., Medicago sp, Trifolium sp.) while arboreal legumes are often found in tropical regions. There are a few options of herbaceous perennial warm-climate legumes, and some of them are still underexploited (e.g. Arachis pintoi, Arachis glabrata). Documented examples of forage legumes increasing livestock productivity are available in different regions of the world, and recent progress has been made in developing and managing forage legume germplasm adapted to biotic and abiotic stresses in tropical America, Africa, Southeast Asia, and Australia. Learning past lessons and applying the knowledge to shape the future is essential to achieve SI of livestock systems

Dairy Cow Performance on Pasture-Based Feeding Systems and in Confinement

Interest in grazing systems is growing among farmers in the USA as a means of reducing feed costs for lactating dairy cows. An experiment was conducted near Gainesville, FL to compare milk production and composition and milk income minus feed costs from two pasture-based systems with those of a conventional confinement housing system over a 276-d period. System 1 was based on a mixture of rye (Secale cereale L.), annual ryegrass (Lolium multiflorum Lam.), crimson clover (Trifolium incarnatum L.), and red clover (Trifolium pratense L.) during the winter-spring seasons and pearl millet (Pennisetum glaucum [L.] R.Br.) during the summerfall seasons. System 2 utilized a rye-ryegrass mixture (no clover) during winter-spring and bermudagrass (Cynodon spp.) during summer-fall. Concurrently, cows managed in free-stall housing at the university farm comprised System 3. Cows in confined housing produced 20% more milk than cows on pasture, but feed cost of grazing cows was about one half that of confined cows. Milk income minus feed costs was $5.56,$5.84, and $5.34 cow-1 d-1 for Systems 1, 2, and 3, respectively

Nitrogen Concentration in Cell Wall of Warm-Season Perennial Grasses

The objectives of this experiment were to evaluate the influence of N fertilizer, age of regrowth, and season on concentration of N in cell-wall fractions of three warm-season perennial grasses (limpograss, [Hemarthria altissima (Poir.) Stapf et C.E. Hubb.], bermudagrass [Cynodon spp.], and bahiagrass [Paspalum notatum Flügge]. The herbage neutral detergent insoluble nitrogen (NDIN) fraction composed almost half of total N in these grasses. Though acid detergent insoluble nitrogen (ADIN) concentrations generally were 80 g kg-1 of total N or less, this fraction is indigestible and unavailable and composes a significant portion of a nutrient that may already be in short supply in warm-season grasses

Nutrient Movements through Ruminant Livestock Production Systems

Considerable attention has been paid to reducing nutrient emissions from ruminant livestock in the last few decades. This area will continue to attract considerable research in the future due to increasing farm sizes in some developed countries as well as the increasing demand for meat and dairy products, particularly in developing countries. This paper discusses the deposition and losses of carbon and nitrogen in soils and plants in grazed and harvested forage systems as well as utilization and losses of both nutrients by ruminants in both systems. The paper also outlines several soil, plant, and animal-focused strategies that can be used to reduce carbon and nitrogen losses from ruminant livestock systems. These strategies will become increasingly important due to the need to feed the growing population of the world while reducing environmental pollution from ruminant livestock systems

Canopy Characteristics and Growth Rate of Bahiagrass Monoculture and Mixtures with Rhizoma Peanut

Understanding relationships among canopy light interception (LI), canopy height and structure, and leaf area index (LAI) informs management decisions and can improve efficiency of forage-livestock systems. In a long-term experiment in Florida, USA, we assessed the LI, LAI and sward height relationships of rhizoma peanut (Arachis glabrata Benth., RP)-bahiagrass (Paspalum notatum Flügge) mixed swards compared with bahiagrass monoculture to determine whether changes in canopy structure affect herbage accumulation (HA) rate due to changes in radiation use. Treatments were arranged in a semi-factorial, split-plot design (r=4). Bahiagrass monoculture and bahiagrass-RP mixtures were whole-plot treatments. Sub-plot treatments were an undefoliated control, forage clipped to 5 cm when LAI \u3e 3, and forage clipped to 5 cm when LAI \u3e 3 and fertilized immediately after with 20 kg N ha-1. During 2021, LI, LAI and canopy height were measured weekly using a LiCOR LAI-2200 and a rising plate meter (platemeters g1000), respectively. The proportion of bahiagrass and RP in total herbage mass was determined for each treatment in July 2021. Herbage accumulation rate was calculated as HA during the regrowth period divided by days between clipping events. The relationship of LI and LAI was assessed with a negative exponential model. Relationships of cumulative LAI and sward height and days after clipping were determined using regression analysis. Incorporating RP into bahiagrass increased LI at shorter sward height compared with bahiagrass monoculture due to a greater LAI mm-1 of sward height (190-220 vs. 150-160 mm). Fertilized mixtures achieved LAI95 faster than bahiagrass monoculture, however, changes in mixture canopy structure did not result in greater radiation-use efficiency compared with fertilized bahiagrass monoculture. Herbage accumulation rate decreased for mixtures containing more than 30% RP. Application of this information can improve the efficiency of grazing systems and maximize HA of bahiagrass-RP mixtures, either under rotational or continuous stocking