Mature Grass Research Articles

Technical note: Improved methodology for analyses of acid detergent fiber and acid detergent lignin

The objective of this study was to evaluate the methodology of the acid detergent lignin (ADL) assay in an effort to evaluate particle loss, improve repeatability, and decrease variation within and among samples. The original ADL method relied on asbestos as a filtering aid, but that was removed in 1989 with the mandate from the Environmental Protection Agency to eliminate asbestos in the environment. Furthermore, recent work on fiber methodology indicated that pore size in the Gooch sintered glass crucible (40–60 μm) was too large to trap all of the small particles associated with neutral detergent fiber (NDF) and acid detergent fiber (ADF). Thus, any loss of ADF could potentially result in a loss of ADL. Sixty forages including conventional and brown midrib corn silages, alfalfa silages and hays, mature grasses, early vegetative grasses, and 9 feces samples, were analyzed sequentially for ADF and ADL as outlined in the 1973 procedure of Van Soest except for the use of the asbestos fiber. A glass microfiber filter with a 1.5-μm pore size was chosen as a filtering aid because it met the criteria required by the assay: glass, heat resistant, acid resistant, chemically inert, and hydrophobic. To compare with the current ADF and ADL assays, the assays were conducted with either no filter or the glass filter inserted into crucibles, rinsed with acetone, and then according to the 1973 procedure of Van Soest. The samples analyzed covered a range from 18.11 to 55.79% ADF and from 0.96 to 9.94% ADL on a dry matter (DM) basis. With the use of the filter, the mean ADF values increased 4.2% and mean ADL values increased 18.9%. Overall, both ADF and ADL values were greater with the use of the glass microfiber filter than without, indicating that as the type of sample analyzed changed, use of the Gooch crucible without the filtering aid results in particle loss. The adoption of the use of a small pore size (1.5 μm) glass microfiber filter to improve filtration and recovery of ADF and ADL and to reduce variation in the ADL assay is recommended, especially when sintered glass bottom crucibles are used. These differences in recovery and repeatability have implications for other fiber and lignin methods, as well as for estimating the potential changes in digestibility of fibrous feeds and feed quality.

In vitro rumen methane output of perennial ryegrass samples prepared by freeze drying or thermal drying (40 °C)

In many in vitro studies feeds are dried in heated ovens with forced air ventilation and milled through a screen with 1mm apertures to obtain a physically representative small sample. Drying methods involving heat have been shown to change the chemical composition of feeds, and it is possible that changes in the chemical composition during thermal drying could affect in vitro rumen CH4 output measured on the samples. Hence, samples are often dried by freeze drying. The objective of this study was to compare effects of freeze drying at −55°C for 72h versus thermal drying at 40°C for 48h on the chemical composition and CH4 output of perennial ryegrass samples collected at 5 stages of primary growth (i.e., 12 May, 26 May, 9 June, 23 June, 7 July) using an in vitro rumen gas production technique. The magnitude of the changes in chemical composition due to drying method was small and not biologically important, and drying method had no effect on CH4 output. With advancing maturity at harvest, digestibility of the herbage declined. Methane output/g dry matter (DM) incubated decreased linearly while CH4 output/g DM digested increased linearly with advancing grass maturity. Thermal drying on a range of grass samples had a similar effect to freeze drying on in vitro rumen CH4 output, reflecting the small degree of change in chemical composition.This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.

Effects of a perennial ryegrass diet or total mixed ration diet offered to spring-calving Holstein-Friesian dairy cows on methane emissions, dry matter intake, and milk production

The objective of the present study was to compare the enteric methane (CH4) emissions and milk production of spring-calving Holstein-Friesian cows offered either a grazed perennial ryegrass diet or a total mixed ration (TMR) diet for 10 wk in early lactation. Forty-eight spring-calving Holstein-Friesian dairy cows were randomly assigned to 1 of 2 nutritional treatments for 10 wk: 1) grass or 2) TMR. The grass group received an allocation of 17kg of dry matter (DM) of grass per cow per day with a pre-grazing herbage mass of 1,492kg of DM/ha. The TMR offered per cow per day was composed of maize silage (7.5kg of DM), concentrate blend (8.6kg of DM), grass silage (3.5kg of DM), molasses (0.7kg of DM), and straw (0.5kg of DM). Daily CH4 emissions were determined via the emissions from ruminants using a calibrated tracer technique for 5 consecutive days during wk 4 and 10 of the study. Simultaneously, herbage dry matter intake (DMI) for the grass group was estimated using the n-alkane technique, whereas DMI for the TMR group was recorded using the Griffith Elder feeding system. Cows offered TMR had higher milk yield (29.5 vs. 21.1kg/d), solids-corrected milk yield (27.7 vs. 20.1kg/d), fat and protein (FP) yield (2.09 vs. 1.54kg/d), bodyweight change (0.54kg of gain/d vs. 0.37kg of loss/d), and body condition score change (0.36 unit gain vs. 0.33 unit loss) than did the grass group over the course of the 10-wk study. Methane emissions were higher for the TMR group than the grass group (397 vs. 251 g/cow per day). The TMR group also emitted more CH4 per kg of FP (200 vs. 174g/kg of FP) than did the grass group. They also emitted more CH4 per kg of DMI (20.28 vs. 18.06g/kg of DMI) than did the grass group. In this study, spring-calving cows, consuming a high quality perennial ryegrass diet in the spring, produced less enteric CH4 emissions per cow, per unit of intake, and per unit of FP than did cows offered a standard TMR diet.

Competitive Ability of Black Henbane (Hyoscyamus niger) When Grown with Three Native Grasses

AbstractBlack henbane is a poisonous, invasive plant in the family Solanaceae, and is typically associated with highly disturbed environments, such as pipelines, roadsides, and mammalian burrows. Often, such disturbances require reseeding for successful restoration; thus, the potential exists for competition between henbane and perennial grasses commonly used in restoration projects. These competitive interactions have not, to our knowledge, been evaluated. We conducted a greenhouse study to compare the response of henbane when grown alone and in combination with three common, cool season, perennial, northern mixed prairie grass species. We examined both seedling and mature grass response to the presence or absence of henbane and the response of henbane to the grasses. Using the relative neighbor-effect index, black henbane was found to be a very poor competitor with mature grasses and two out of three seedling grasses tested. All measures of henbane growth were significantly lower among plants grown with a mature grass pot companion. Total biomass of henbane was up to 99% lower when grown with mature grasses. Mature grasses were not negatively affected when grown in combination with henbane. Western wheatgrass (Pascopyrum smithii) was the only seedling grass that was competitive with henbane but was also the only seedling grass negatively affected by henbane in both biomass and tiller production. These experiments suggest that henbane is not well suited for invasion of mature grass stands but may negatively influence some perennial grass seedlings in restoration situations.

Exotic C4Grasses Have Increased Tolerance to Glyphosate under Elevated Carbon Dioxide

The increase in atmospheric CO2levels can influence the growth of many invasive exotic plant species. However, it is not well-documented, especially for C4plants, how these growth responses will alter the effectiveness of the world's most widely used herbicide for weed control, glyphosate. We aimed to address this question by carrying out a series of glasshouse experiments to determine if tolerance to glyphosate is increased in four C4invasive exotic grasses grown under elevated CO2in nonlimiting water conditions. In addition, traits including specific leaf area, leaf weight ratio, leaf area ratio, root : shoot ratio, total leaf area, and total biomass were measured in order to assess their contribution to glyphosate response under ambient and elevated CO2levels. Three of the four mature grass species that were treated with the recommended concentration of glyphosate displayed increased tolerance to glyphosate under elevated CO2. This was due to increased biomass production resulting in a dilution effect on the glyphosate within the plant. From this study, we can conclude that as atmospheric CO2levels increase, application rates of glyphosate might need to be increased to counteract the growth stimulation of invasive exotic plants.

Fibrolytic potential of spent compost of the mushroom Agaricus bisporus to degrade forages for ruminants

To evaluate the fibrolytic potential to degrade forages, extracts from spent compost ofAgaricus bisporus (SCAB) were evaluated in vitro. Firstly, SCAB was cultivated for 50, 60 and 90 days (culture stage) and enzyme activity was evaluated. The highest cellulase activity was at 60 days; xylanase activity was not affected by culture stage and laccase activity increased as culture stage increased. Secondly, extracts of SCAB cultivated for 60 days were preserved by refrigeration, freezing, freeze-drying, refrigeration + benzoic acid, freezing + benzoic acid, freezing + glycerol, or freezing + benzoic acid-glycerol and then fibrolytic activity was evaluated. The highest fibrolytic activity was shown by SCAB frozen with addition of either glycerol or benzoic acid, or freeze-dried. Finally, effects of SCAB as an additive to enhance ruminal degradation of alfalfa hay, Taiwan grass, barley straw, and spent compost of A. bisporus were evaluated. Soluble fraction of dry matter of alfalfa and potential degradation of dry matter of Taiwan grass and barley straw were increased by SCAB. It is concluded that SCAB showed a noticeable fibrolytic activity which might increase degradation of forages in the rumen. Key words: Agaricus bisporus, degradation, fibrolytic enzymes, forages, ruminants.

Grass leaf protein, a coproduct of cellulosic ethanol production, as a source of protein for livestock

Leaf protein (LP) produced as a coproduct of cellulosic ethanol production can be utilized by livestock. Effects of conservation method on protein extraction efficiency from orchardgrass (OG) and switchgrass (SG); effects of grass maturity, chemical and heat treatment, and conservation method on protein degradation of LP from OG; and amino acid profiles of OG and LP from OG before and after degradation were evaluated. Two maturities of OG and SG were harvested in 2008 with crude protein (CP) concentrations of 171 and 44 g/kg dry matter (DM; immature) and 131 and 24 g/kg DM (mature) for OG and SG, respectively. Grasses (fresh, stored, or wilted) were chopped, juice extracted with a screw press and adjusted to a pH of 3.3 with concentrated HCl, and treated with or without zinc and with heat (100 or 140 °C for 1 h) or without heat (21 °C; control) followed by centrifugation to harvest precipitated LP. Efficiencies of extraction were similar for fresh and stored, which were both higher than wilted grass (P < 0.01). Crude protein concentrations (g/kg DM) of LP were approximately twice that of the original grass for all chemical and heat treatment combinations. In vitro protein degradation of OG LP was evaluated using enzymes extracted from rumens of lactating dairy cows. Fresh OG LP treated with HCl + Zn 140 °C had the greatest reduction in CP degradation compared to HCl control. An interaction (P < 0.05) between maturity and zinc was observed with zinc decreasing CP degradation of immature OG LP more than mature OG LP after 4 h incubation. Interactions (P < 0.10) were also detected between maturity and temperature and between chemical and temperature after 12 h incubation. Heat decreased CP degradability with temperatures of 100 °C and 140 °C resulting in similar degradation (42.9 and 39.5 g/kg CP, respectively), which were lower than control (112.9 g/kg CP; P < 0.05) after 4 h incubation. There was an effect of conservation method on HCl + Zn 140 °C treated OG LP with similar degradability for stored (51.5 g/kg CP) and wilted (83.0 g/kg CP), which were higher than fresh (16.8 g/kg CP; P < 0.05) after 4 h incubation. The amino acid patterns of OG LP before and after degradation were similar. In summary, LP from fresh grass is most suitable because proteolysis during storage or wilting likely decreases protein recovery and increases ruminal degradation, and both zinc and heat treatments decrease degradability of OG LP within the rumen.

Development and Evaluation of a Prototype Precision Spot Spray System Using Image Analysis to Target Guinea Grass in Sugarcane

Herbicide usage in weed control represents a significant economic cost and environmental risk in Australian sugarcane production. Weed spot spraying has potential to increase sugarcane production while reducing chemical usage and environmentally damaging runoff. However, weed spot spraying is traditionally a laborious manual task. This paper reports on a precision machine vision system that was developed to automatically identify and target the difficult to control weed Panicum spp. (Guinea Grass) in sugarcane crops. The infield machine vision system comprised a camera and artificial illumination to enable day and night trials. Image analysis algorithms were developed to discriminate Guinea Grass and sugarcane based on colour and textural differences between the species. A positive weed identification from the image analysis activated solenoid-controlled spray nozzles. Evaluations of the system in a sugarcane crop established that the image analysis algorithm parameters required frequent recalibration during the day but that the requirement for recalibration was reduced at night with constant artificial illumination. The algorithm was only effective at detecting mature Guinea Grass. The developed technology is considered a viable alternative to manual spot spraying of mature Guinea Grass in sugarcane at night. A cost benefit analysis of the new weed control system indicated potential grower savings of $170/ha by adopting the technology.

Ruminal degradability of dry matter and neutral detergent fibre of grasses

A study was conducted (I) to determine rumen degradability (in sacco) of dry matter (DM) and neutral detergent fibre (NDF) of the most important grass species grown in the Czech Republic, (II) to compare grass species (n = 5) according to calculated degradation parameters, and (III) to establish prediction equations for degradation parameters from chemical composition. Forty samples of the most important grass species (Dactylis glomerata, Phleum pratense, Lolium perenne, Festuca arundinacea, Felina hybrid) were harvested in 2004 and 2005 and analyzed for chemical composition, and DM and NDF in sacco degradability. Results from the in sacco method were used to calculate DM and NDF degradation parameters. Linear and stepwise multiple regression analyses were used to develop prediction equations for DM and NDF degradation parameters from nutrient concentrations. The highest DM and NDF degradation parameters were found for Lolium perenne. DM and NDF rumen degradation parameters were successfully predicted from chemical composition, with a single predictor adequate for most parameters. For all parameters R&lt;sup&gt;2&lt;/sup&gt;-values increased with addition of more predictors into regression equations. Effective degradability (ED) of DM calculated at a rumen outflow rate (k) of 0.05 h&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; was the best predicted by NDF (R&lt;sup&gt;2&lt;/sup&gt; = 0.878), and ED of NDF at k = 0.02 h&lt;sup&gt;&amp;ndash;1&lt;/sup&gt; by crude protein (CP) (R&lt;sup&gt;2 &lt;/sup&gt;= 0.653).

Influence of compost covers on the efficiency of biowaste composting process

The temperature of matured compost is an indicator of feedstock quality and also a good feedback informing about the suitability of an applied technological procedure. Two independent experiments using the technology of windrow composting at open area were conducted with the final goal to evaluate the effect of compost pile covering (in comparison with uncovered piles) on the course of composting process – behaviour of temperature over time and oxygen content. Two types of sheets were used – Top Tex permeable sheet and impermeable polyethylene sheet. The experiment I (summer months) aimed at comparison of efficiency between the Top Tex sheet cover and the uncovered compost piles, while experiment II (autumn months) compared treatments using the Top Tex sheet and polyethylene sheet by contrast. Within the experiment I the composts consisted of cattle slurry and fresh grass matter at a ratio of 1:1, in case of experiment II consisted of pig/cattle manure, fresh grass matter and chipped material at a ratio of about 1:2:1. The obtained data showed no significant differences among the cover treatments according to ANOVA. The only exception was oxygen content in pile 4 (experiment II) under Top Tex sheet, where a markedly higher oxygen content than under polyethylene sheet was measured during the whole composting period. It was the only case where statistical analysis proved a significant difference; the p-value was 0.0002.

Produção de biomassa e estrutura do pasto de capim-andropogon em sistema silvipastoril e monocultura

A produção de biomassa e as características estruturais do capim-andropogon foram avaliadas nas idades de rebrota de 35, 49 e 63 dias, em três ambientes de um sistema silvipastoril: sob a copa de pau-d'arco, sob a copa de jatobá, em área aberta; local fora da copa de qualquer árvore e em sistema de monocultura. O delineamento experimental foi o de parcelas subdivididas com cinco repetições. As parcelas foram representadas pelos ambientes e as subparcelas, pelas idades de rebrota. A luminosidade sob pau-d'arco, sob jatobá e em área aberta foi de 74, 62% e 82%, respectivamente, das áreas a pleno sol. Houve interação ambiente versus idade de rebrota. O sombreamento sob a copa de pau-d'arco e de jatobá não afetou a produção de matéria seca do capim-andropogon, contudo reduziu a altura do pasto aos 63 dias de rebrota. O percentual de folhas da forragem aos 35 dias de rebrota foi mais elevado na monocultura. Nas outras idades de rebrota, os quatro ambientes não diferiram entre si.

Agrochemical value of the liquid phase of wastes from fermentem during biogas production

We tested the procedure of combined phytomass utilization Integrated Generation of Solid Fuel and Biogas from Biomass (IFBB) proposed for ensiled grass matter from the aspect of suitability of its use for a typical substrate of new Czech biogas stations, a mixture of cattle slurry, maize silage and grass haylage. The agrochemical value of the liquid phase from a biofermenter was also evaluated. We concluded that this procedure is suitable for the tested substrate and improves the agrochemical value of a fugate from biogas production. By chlorine transfer to the liquid phase, it enables to use the solid phase as a material for production of solid biofuels with a reduced threat of the generation of polychlorinated dioxins and dibenzofurans during combustion. However, the concentration of mineral nutrients in the liquid phase during IFBB procedure is extremely low after anaerobic digestion as a result of dilution with water, and so its volume value is negligible.

Simulating the effects of grassland management and grass ensiling on methane emission from lactating cows

SUMMARYA dynamic, mechanistic model of enteric fermentation was used to investigate the effect of type and quality of grass forage, dry matter intake (DMI) and proportion of concentrates in dietary dry matter (DM) on variation in methane (CH4) emission from enteric fermentation in dairy cows. The model represents substrate degradation and microbial fermentation processes in rumen and hindgut and, in particular, the effects of type of substrate fermented and of pH on the production of individual volatile fatty acids and CH4as end-products of fermentation. Effects of type and quality of fresh and ensiled grass were evaluated by distinguishing two N fertilization rates of grassland and two stages of grass maturity. Simulation results indicated a strong impact of the amount and type of grass consumed on CH4emission, with a maximum difference (across all forage types and all levels of DMI) of 49 and 77% in g CH4/kg fat and protein corrected milk (FCM) for diets with a proportion of concentrates in dietary DM of 0·1 and 0·4, respectively (values ranging from 10·2 to 19·5 g CH4/kg FCM). The lowest emission was established for early cut, high fertilized grass silage (GS) and high fertilized grass herbage (GH). The highest emission was found for late cut, low-fertilized GS. The N fertilization rate had the largest impact, followed by stage of grass maturity at harvesting and by the distinction between GH and GS. Emission expressed in g CH4/kg FCM declined on average 14% with an increase of DMI from 14 to 18 kg/day for grass forage diets with a proportion of concentrates of 0·1, and on average 29% with an increase of DMI from 14 to 23 kg/day for diets with a proportion of concentrates of 0·4. Simulation results indicated that a high proportion of concentrates in dietary DM may lead to a further reduction of CH4emission per kg FCM mainly as a result of a higher DMI and milk yield, in comparison to low concentrate diets. Simulation results were evaluated against independent data obtained at three different laboratories in indirect calorimetry trials with cows consuming GH mainly. The model predicted the average of observed values reasonably, but systematic deviations remained between individual laboratories and root mean squared prediction error was a proportion of 0·12 of the observed mean. Both observed and predicted emission expressed in g CH4/kg DM intake decreased upon an increase in dietary N:organic matter (OM) ratio. The model reproduced reasonably well the variation in measured CH4emission in cattle sheds on Dutch dairy farms and indicated that on average a fraction of 0·28 of the total emissions must have originated from manure under these circumstances.

Review of the Integrated Process for the Production of Grass Biomethane

Production of grass biomethane is an integrated process which involves numerous stages with numerous permutations. The grass grown can be of numerous species, and it can involve numerous cuts. The lignocellulosic content of grass increases with maturity of grass; the first cut offers more methane potential than the later cuts. Water-soluble carbohydrates (WSC) are higher (and as such methane potential is higher) for grass cut in the afternoon as opposed to that cut in the morning. The method of ensiling has a significant effect on the dry solids content of the grass silage. Pit or clamp silage in southern Germany and Austria has a solids content of about 40%; warm dry summers allow wilting of the grass before ensiling. In temperate oceanic climates like Ireland, pit silage has a solids content of about 21% while bale silage has a solids content of 32%. Biogas production is related to mass of volatile solids rather than mass of silage; typically one ton of volatile solid produces 300 m(3) of methane. The dry solids content of the silage has a significant impact on the biodigester configuration. Silage with a high solids content would lend itself to a two-stage process; a leach bed where volatile solids are converted to a leachate high in chemical oxygen demand (COD), followed by an upflow anaerobic sludge blanket where the COD can be converted efficiently to CH(4). Alternative configurations include wet continuous processes such as the ubiquitous continuously stirred tank reactor; this necessitates significant dilution of the feedstock to effect a solids content of 12%. Various pretreatment methods may be employed especially if the hydrolytic step is separated from the methanogenic step. Size reduction, thermal, and enzymatic methodologies are used. Good digester design is to seek to emulate the cow, thus rumen fluid offers great potential for hydrolysis.

Effect of a Yeast Culture on Nitrogen Balance and Digestion in Lambs Fed Early and Mature Orchard Grass

Hernández, R., González, S.S., Pinos-Rodríguez, J.M., Ortega, M.E., Hernández, A., Bueno, G. and Cobos, M. 2009. Effect of a yeast culture on nitrogen balance and digestion in lambs fed early and mature orchard grass. J. Appl. Anim. Res., 35: 53–56. To evaluate the effect of feeding a yeast culture (0 or 5 g/d per sheep) on digestion and N balance in lambs fed orchard grass hay cut at 5 or 16-wk of re-growth, 4 male Criollo lambs (45 ± 4 kg) fitted with ruminal cannulae in a 4x4 Latin square with a factorial 2x2 arrangement of treatments were used. Addition of a yeast culture did not affect (P>0.05) intake, rumen pH and ammonia N, N balance and total tract digestion of nutrients. Ruminal total protozoa changed only according to orchard grass maturity (P<0.05); however, treatments did not affect total and cellulolytic bacteria, rumen pH and rumen ammonia N concentration. It is concluded that addition of a yeast culture to lambs fed early and mature orchard grass did alter ruminal protozoa without affecting feed intake, total tract digestion and N balance.

Chemical composition and in vitro ruminal fermentation of selected grasses in the semiarid savannas of Swaziland

Little is known about the grass species type, composition and nutritive value in the semiarid savannas that sustain most of Swaziland's cattle population through the seven-month-long dry season. This study was conducted to investigate the nutritional characteristics of grasses collected from two grazing areas (Big Bend and Simunye), which differed mainly in soil types. Mature grass species were harvested and evaluated for chemical composition (organic matter, neutral detergent fibre [NDF], acid detergent fibre [ADF], crude protein [CP] and minerals) and in vitro ruminal fermentation (in vitro gas production, in vitro organic matter degradability and partitioning factors). The most common grass species in the Big Bend grazing area were Bothriochloa insculpta, Cenchrus ciliaris and Urochloa mosambicensis. In the Simunye grazing area the most common species were B. insculpta, U. mosambicensis, Heteropogon contortus, Panicum deustum and P. maximum. For grasses harvested from Simunye, the most (P < 0.05) degradable (532 mg g−1 dry matter) was B. insculpta, which also had the least fibre (597 g kg−1 NDF and 351 g kg−1 ADF) and the highest CP content (79.8 g kg−1). The most common grass species harvested from the Big Bend area did not differ (P > 0.05) in their Mg, P, Cu, Fe, Zn, CP and NDF content. However, U. mosambicensis had the highest (P < 0.05) ADF content. The least fermentation efficiency (partitioning factor = 2.2 mg degradable organic matter [DOM] ml−1 gas) was observed for U. mosambicensis as a result of low DOM coupled with high cumulative gas production. It was concluded that all the grasses investigated in this study show a deficit for Ca, P and protein. Therefore, supplementation is needed to ensure maximum forage utilisation and to satisfy nutrient requirements of ruminant livestock.

Intake and Digestibility by Yankasa Sheep of Diets Containing Different Proportions of Legumes and Mature Grass (Cynodon nlemfuensis)

A total of 20 yankasa sheep with liveweights ranging from 25 kg were used in a completely randomized experiment to assess the effect of combining tropical legume (Stylosanthes guyanensis) with a mature grass (Cynodon nlemfuensis) on intake and digestibility of these animals. Experimental diets were grass alone (Cynodon nlemfuensis), 3 combinations of Cynodon nlemfuensis and Stylosanthes guyanensis (10%, 20%, 30%), and Stylonsanthes guyanensis alone. There were 4 sheep in each treatment. The experiment lasted 4 weeks being made up of 3 weeks of feeding and 1 week of collection. Parameters of evaluation were the nutrient composition of the feed, the nutrient intake and digestibilities. The result indicated that the intake of mature Cynodon nlemfuensis increased with inclusion of Stylosanthes guyanensis in the forage offered. Total dry matter (DM) and other nutrient intake increased appreciably (P JARD Vol. 3 2004: pp. 1-6

Intake, Digestibility In vivo, N Utilization and In sacco Dry Matter Degradability of Grass Silage Harvested at Three Stages of Maturity

The objective of this experiment was to study the effects of grass maturity at harvest on the nutritive value of grass silage (GS) in relation to voluntary intake, digestibility, nitrogen (N) utilization and in sacco dry matter (DM) degradability. Silage was cut from a sward dominated by orchardgrass (Dactylis glomerata L.) at the late-vegetative (early-cut), internode elongation (medium-cut) and flowering (late-cut) stages of growth. The DM yield at harvest was the lowest for early-cut silage (5.4 t/ha) and increased to 6.5 and 7.0 t/ha for the medium and late-cut silage respectively. As the crop matured, the crude protein (CP) concentration decreased significantly (p < 0.05) and there was a marked increase in acid detergent fiber (ADF) concentration (p < 0.001). The three different silages were offered to four 18-month old Charolais wether sheep to measure the voluntary intake, in vivo digestibility and N retention over four 21-day periods in an incomplete changeover design. Silage degradability characteristics were determined using four fistulated sheep to measure DM degradability over 3, 6, 12, 24, 48 and 72 h. There was a linear decrease in the voluntary intake of silage fresh matter, DM, organic matter (OM) and neutral detergent fiber (NDF), digestibility of DM, OM, NDF, ADF and CP, and digestibility of OM in DM (D-value) (P-L < 0.01) as harvesting of grass was delayed. Nitrogen intake, N output in urine. N output in faeces and N balance also linearly decreased (P-L < 0.01) with postponed harvesting of grass for silage. DM degradability and effective degradability (ED) significantly decreased with increasing maturity of grass at harvest. The results suggest that harvesting date has a significant influence on the nutritive value of GS in terms of intake, digestibility, N balance and in sacco degradability in the rumen. It was concluded that early harvest GS ensured higher intake, digestibility, N intake and DM degradability in comparison with the medium and the late cut GS as a result of improved rumen N efficiency and utilization probably due to a better balance of available energy and protein.

Stage‐dependent border cell and carbon flow from roots to rhizosphere

Rising CO(2) levels in the atmosphere have drawn attention to the important role of soil in sequestering carbon. This project goal was to quantify soil carbon deposition associated with border cell release and exudation from root growth zones. Carbon was measured with a Carlo Erba C/N analyzer in soil from the rhizosphere of mature grasses and, in separate experiments, in soil collected around root growth zones. Root border cells in "rhizosphere soil" (silica sand) were counted using a compound microscope after soil sonication and extraction with surfactant. For sand-grown Bromus carinatus, Zea mays, and Cucumis sativus, young seedlings (with roots shorter than 2 cm) released thousands of border cells, while older root tips released only hundreds. For a variety of native annual and perennial grasses and invasive annual grasses (Nassella pulchra, B. carinatus, B. diandrus, B. hordeaceus, Vulpia microstachys, Aegilops triuncialis, Lolium multiflorum, Zea mays), the rhizosphere of mature root systems contained between 18 and 32 μg C g(-1) sand more than that of the unplanted controls. Spatial analysis of the rhizosphere around the cucumber growth zone confirmed C enrichment there. The root tip provided C to the rhizosphere: 4.6 μg C in front of the growing tip, with the largest deposition, 20.4 μg C, to the rhizosphere surrounding the apical 3 mm (root cap/meristem). These numbers from laboratory studies represent the maximum C that might be released during flooding in soils. Scaling up from the organ scale to the field requires a growth analysis to quantify root tip distributions in space and time.

Diferentes métodos de controle de plantas indesejáveis em pastagem nativa

O experimento foi desenvolvido em área de pastagem nativa representativa da transição entre a Serra do Sudeste e a Depressão Central do Rio Grande do Sul, onde as espécies indesejáveis foram representadas especialmente por carqueja (Baccharis trimera (Less.) DC.), caraguatá (Eryngium horridum (Spreng.) Less.) e alecrim (Vernonia nudiflora Less.). Foram avaliados os efeitos iniciais de dois métodos de controle de espécies indesejáveis (até 60 dias após aplicação) sobre a produção de forragem, a dinâmica da vegetação e a eficiência de controle: sem-controle; controle mecânico; e controle químico (herbicida comercial à base de Picloram [64 g/L] + 2,4-D [240 g/L], na dosagem de 5 L do produto comercial/ha). Os tratamentos foram arranjados em um delineamento em blocos ao acaso, com quatro repetições. A massa gramíneas verdes secas e a massa total de MS não diferiram entre os métodos de controle. Foram obtidos valores de 587,9; 472,0 e 0 kg de MS com o controle mecânico, o controle químico e sem-controle, respectivamente, o que comprova influência do método de controle sobre a massa de forragem de leguminosas. A eficiência de controle das espécies indesejáveis, em comparação à ausência de controle, foi de 76,2% para o controle químico e 27,9% para o controle mecânico. A eficiência de controle de espécies, sob aspectos de freqüência dos componentes da pastagem, evidenciou que o controle mecânico não foi eficiente aos 60 dias após aplicação no controle de plantas de alecrim no segundo toque (-27,7%) e plantas de caraguatá no primeiro toque (-30,0%).