Mature Grass Research Articles

Herbage leaf to stem ratio and yield distribution of ime as influenced by cutting frequency and N-fertilizer application in an old run-down <i>Panicum maximum </i> pasture

In a sandy loam soil at Nsukka, the effects of cutting management and fertilizer-N treatment on revitalization of a run-down pasture were investigated in 2000 and 2001. Increasing the interval between cuts from 3 to 12 weeks increased the proportion of stem relative to leaf blade in the grass herbage in the second year. The proportion of leaf to stem at 3-weekly interval of cuts was 54.6:1; this ratio had fallen to 13.3:1 at 6 weeks, 4.7:1 at 9 weeks and 7:1 at the 12 weekly cutting intervals. Incremental application of fertilizer N led to increase in the proportion of stem relative to the leaf blade in the grass herbage. The proportion of leaf to stem when N was not applied was 12.7:1; this ratio had fallen to 11:1 at 150kg ha -1 , 7.7:1 at 300kg ha -1 and 6.9:1 at the highest N-rate of 450kg ha -1 . The 6-week interval of cuts yielded significantly higher dry matter of grass herbage than the 3 - weekly intervals in most of the periods considered. Grass herbage yield picked up early in the year and increased with advancing season up to about early October and then decreased in both years. Increasing the interval between harvests from 3 to 6 weeks increased the dry matter yields of leaf, stem and inflorescence in all the periods considered. Fertilizer-N treatment significantly increased grass herbage yield in most of the periods. A combination of 6 - weekly interval of cuts with 450kg ha -1 gave the highest forage grass herbage dry matter yield. Keywords : Leaf to stem ratio, Yield distribution, Cutting Frequency, N – Fertilizer Agro-Science Vol. 4 (1) 2005: pp. 74-77

Effect of maturity on the mineral content of Columbus grass (<i>Sorghum almum</i>)

This study was conducted in Naivasha, Kenya over a period of 15 weeks to determine the effect of maturity on mineral content in Columbus grass ( Sorghum almum ). Immediately after field preparation, representative soil samples were taken for mineral profiling. Thereafter, 60 plots 2 x 2 sq. m size were demarcated and allotted to 5 similar blocks of 12 plots each in a randomized complete block (RCB) design. Each plot received 25 g of seed evenly drilled to 5 rows (2 m length and 30 cm apart). All the plots were planted on the same day and kept weed free throughout the study. The grass was harvested at 6, 8, 10, 12 and 14 weeks after seed emergence in sequential manner beginning with block 1 to 5, each time leaving a stubble height of 5 cm. From each plot, representative herbage grabs were made, chopped into 2 cm pieces and mixed thoroughly. Two composite samples of about 500 g each were then taken for dry matter determination and mineral analysis using the standard procedures. Results showed that, the plant tissue levels of all mineral elements investigated were significantly affected by advancing grass maturity. Between 6 and 14 weeks, P and K decreased by 35.14 and 46.77% respectively. It was also noted that Na, Ca and Mg decreased by 46.49, 20.41 and 21.74% over the same period. Levels of trace elements also declined as the grass matured. Results showed that Cu, Mn and Zn levels decreased by 36.4, 27.4 and 57.1% respectively, between 6 and 14 weeks. Ca:P ratios however remained consistent over this period. It was generally observed that, although levels of macro-elements declined with advancing maturity of the grass, their overall concentrations remained within the recommended requirements for ruminant production. Trace element levels were generally below those desired for ruminant production. It was therefore concluded that macro-mineral elements might not be a problem in Sorghum almum based diets. Ruminants would however require additional source of trace elements to correct possible deficiencies of the same in their diets. Keywords : Macro–elements; Micro-elements; Ruminants; Diets; Supplementation Animal Production Research Advances Vol. 2 (3) 2006: pp. 134-138

Evaluation Studies on the Dry Matter Production and Quality of Annual and Perennial Grasses

A field experiment for determining dry matter and quality of annual and perennial grasses was conducted during 2005 and 2006 at Cattle Research Station, Manasbal on a silty clay loam soil that was low in available nitrogen, medium in available phosphorus and potassium, with neutral pH. The treatments consisted of one annual grass (Oat, Avena sativa L.) and four perennial grasses (orchardgrass, Dactylis glomerata L.; perennial ryegrass, Lolium perenneL.; tall fescue, Festuca arundinacea L.; and hybrid Phalaris, Phalaris stenoptera L.). Dry matter yields of oat at first cutting on 15 April 2005 (8.05 Mg/ha) and 15 April 2006 (8.10 Mg/ha) were similar to hybrid Phalaris (7.23 and 7.74 Mg/ha during 2005 and 2006, respectively) but were significantly greater than other grasses, while dry matter yields of hybrid Phalaris at second cutting during 2005 (5.21 Mg/ha) and 2006 (5.27 Mg/ha) were significantly greater than oat and other grasses. The plant height of hybrid Phalaris at first cutting during both years was significantly greater than oat and other grasses, while at second cutting on 25 May 2005 and 2006 both hybrid Phalaris and oat were similar but significantly taller than other grasses. Crude protein content of hybrid Phalaris at two cuttings during both the years was significantly greater than oat and other perennial grasses, while crude fiber of the perennial grasses was significantly more than oat except at second cutting on 25 May 2005. In conclusion, hybrid Phalaris gave significantly greater plant height, more dry matter, and higher crude protein content, while tall fescue gave significantly more crude fiber during both years.

Closed-loop wool carpet recycling

Disposal of post-consumer carpets produces large volumes of waste for landfills where they do not readily degrade. Incineration is only possible in countries with the necessary infrastructure and increasing environmental pressure makes incineration unsustainable. We have shown that wool carpets can be used as a fertiliser with excellent results. Ground-up wool carpet, when added to the soil, greatly increases the yield (wet and dry matter) of grass grown. This closed-loop cycle (i.e., grass-wool-carpet-grass) is an efficient form of fibre recycling because the carpet to grass step is solar powered, unlike recycling of synthetic fibres. The suitability of ground-up wool carpets as fertiliser is confirmed by elevated levels of essential elements such as nitrogen (19%), sulphur (19%) and magnesium (7%) in the grass grown on carpet fertilised plots as compared to the control grass. The environmental soundness of wool carpet has been supported by the results of this simple experiment.

The effect of feeding a low- or a high-starch diet on thein vitrofermentative capacity of equine faecal inocula

AbstractSeven mature Welsh-cross pony geldings provided the faecal inocula in a cross-over design experiment, consisting of two 14-day periods. In period 1, four ponies (group 1) were offered a low-starch fibre mix (LS), and three (group 2) were offered a conventional high-starch coarse mix (HS). Both groups were offered these mixes in a 50:50 ratio with mature grass hay, to give a total daily dry-matter intake of 17·5 g/kg live weight per day. Diets were then switched in period 2. At the end of each experimental period freshly voided faeces were collected from each animal and assessed for their ability to ferment grass hay (H), fibre mix (FMix) or starch-based coarse mix (SMix) using the gas production (GP) technique of Theodorouet al.(1994). Donor animal diet and donor animal had no effect on any end-point measurements. Lag times recorded for the SMix were significantly (P<0·001) greater in LS-inoculated bottles compared with the HS inocula (1·74v.2·25 h, respectively). Lag times for FMix and SMix varied significantly (P<0·001) between ponies (0·82 to 1·78 h in the FMix and 1·64 to 2·51 h in the SMix). The degradation rate of H also differed significantly (P<0·001) between ponies with the time taken to reach 50% of GP (T50) ranging from 12·70 to 17·30 h. Consequently, it would appear that the effect of feeding LS or HS on thein vitrofermentative capacity of equine faecal inocula is minimal; moreover, the GP technique appears to be valuable tool for evaluating such effects.

Performance of growing heifers fed urea treated fresh rice straw supplemented with fresh, ensiled or pelleted cassava foliage

Abstract Sixty-eight growing heifers were used in three experiments to evaluate the effects on feed intake, growth, liver enzymes and thyroid hormone status of four supplemental levels of cassava foliage: 0 (T0), 50 (T50), 75 (T75) and 100 g (T100) crude protein 100 kg− 1 LWt provided by fresh, ensiled or pelleted cassava foliage in diets based on urea treated fresh rice straw (UFRS) ad libitum, 0.72 kg dry matter (DM) of napier grass and 0.26 kg DM of cassava root meal (CRM) 100 kg− 1 LWt. The ensiled cassava foliage (ECF) supplement experiment was conducted from June to October in 2002, and the fresh (FCF) and pelleted (PCF) cassava foliage supplement experiments from February to June and August to December in 2003, respectively. The results showed that increasing the level of cassava foliage supplementation in the all experiments slightly decreased UFRS intake (p 0.05) in the PCF and ECF supplement experiments. It is concluded that FCF with its high HCN and condensed tannin content was slightly unpalatable, had a negative effect on circulating thyroid hormones at higher supplemental levels and an adverse effect on growth rate, while ECF and PCF supplementation resulted in improved growth rate without adverse effect on thyroid hormones and feed intake when fed to growing heifers.

EFECTO DE LA ADICIÓN DE COMPOST SOBRE PROPÁGULOS MICORRÍCICOS ARBUSCULARES EN UN SUELO VOLCÁNICO DEL CENTRO SUR DE CHILE

legume, cereal, organic agriculture, arbuscular mycorrhiza. ABSTRACT Organic amendments affect the chemical and biological characteristics of soils rganic amendments affect the chemical and biological characteristics of soils contributing to the sustainability of agroecosystems. The aim of this study was to evaluate in glasshouse conditions the effect of compost addition in an Ultisol on fungal propagules such as those colonized in the roots, mycelium and spores, together with soil chemical and nutritional characterization of three crops (wheat, beans and grass) after harvesting. Compost was based on cattle and vegetables waste and it was supplied into the soil at 0, 8, 20 and 30 Mg ha -1 on dry bases. Roots from all crops presented high arbuscular mycorrhizal fungi (AMF) colonization with the highest amount, while the hyphal length was significantly different only in beans crop. There were not significant differences for the spore numbers. The highest production of dry matter in beans and grass was reached with the highest compost supplied but in wheat this was true for the middle amount of compost. Similar results were obtained for the content of phosphorus (P) in the shoot. Compost application incremented the availability of P in the Ultisol for the three crops. It was concluded that compost application to the three crops studied was beneficial because the high viability of mycorrhizal propagules together with the great amount of phytomass and soil nutrients availability.

Influence of regrowth time on the forage quality of prairie grass, perennial ryegrass and tall fescue under non-limiting soil nutrient and moisture conditions

The influence of regrowth time on the forage quality of prairie grass (Bromus willdenowii Kunth. cv. Matua), perennial ryegrass (Lolium perenne L. cv. Dobson) and tall fescue (Festuca arundinacea Schreb. cv. Dovey) was determined under non-limiting soil nutrient and moisture growth conditions. In a glasshouse, individual plants of each species were arranged in separate mini-swards and were defoliated at 6, 10 and 14 weeks after sowing to a stubble height of 60 mm for perennial ryegrass and tall fescue and 90 mm for prairie grass. Following defoliation at 14 weeks, selected individual plants were cut to the previous stubble height as each new leaf per tiller was fully expanded, to provide leaf material for nutrient analysis, until prairie grass, perennial ryegrass and tall fescue had attained 6–8, 5 and 3 leaves/tiller, respectively. The concentration of leaf phosphorus (P) decreased from 6.6 to 5.9 g/kg dry matter (DM) in prairie grass, increased from 5.9 to 6.9 g/kg DM in perennial ryegrass, and initially increased to 8.8 g/kg DM and then decreased to 8.4 g/kg DM in tall fescue. The mean potassium (K) content in perennial ryegrass was 29.6 g/kg DM and was not significantly affected by duration of regrowth, whereas K content in prairie grass and tall fescue fell from 51.7 to 43.6 g/kg DM and from 55.5 to 47.9 g/kg DM, respectively, after the first leaf per tiller formed. Calcium levels increased with regrowth in all species and at the completion of regrowth were 5.8, 3.8 and 3.4 g/kg DM in prairie grass, perennial ryegrass and tall fescue, respectively. The magnesium (Mg) and sodium (Na) content of perennial ryegrass showed no change throughout the regrowth period and had measured values of 2.5 and 2.8 g/kg DM, respectively. For tall fescue, the concentration of leaf Mg decreased from 0.30 to 0.24 g/kg DM, whereas the Na concentration increased from 1.2 to 2.1 g/kg DM. The Mg content of prairie grass remained constant at 2.0 g/kg DM, whereas the Na content increased from 2.7 to 4.3 (g/kg DM). While the crude protein content of all grasses declined over the regrowth period, values remained over 200 g/kg DM, well above the recommended content for lactating cows. The leaf water-soluble carbohydrate (WSC) of prairie grass and perennial ryegrass increased over the regrowth period from 29.7 to 43.9 g/kg DM and from 25.9 to 72.5 g/kg DM, respectively, whereas tall fescue showed no change at 55.6 g/kg DM. The change in in vitro organic matter digestibility (OMD) with age was 125 and 44 (g/kg DM) for tall fescue and perennial ryegrass, respectively. The OMD of prairie grass decreased following the onset of stem elongation at the 5-leaves/tiller stage of regrowth from 824 to 756 g/kg DM. In this glasshouse study, the pattern of change in K and Ca content was the same as observed in the field but the absolute content, including that of Na, was greatly elevated, particularly in prairie grass. In terms of nutrient content capability, N, P and K were readily taken up by these C3 grasses, while the uptake of Mg and Na appear to reflect genetic differences between species. The differences in forage quality as determined under optimal growth conditions in this study, as compared with field grown forage, are presumed to indicate possible soil nutrient deficiencies in field situations.

Digestion kinetics of leaf, stem and inflorescence from five species of mature grasses

AbstractThe objective of this study was to measure the digestion kinetics for mature (green and non‐senescent) components of five grass species using in sacco and in vitro incubations to define rates of degradation and nutrient release. Mature perennial ryegrass, tall fescue, Yorkshire fog, phalaris and paspalum were hand separated into leaf blade, stem and inflorescence (flower head) for incubations. Concentrations of neutral detergent fibre (NDF) in fractions were in the ranges 492–677 (leaf), 626–718 (stem) and 501–677 (inflorescence) g kg−1 dry matter (DM). Crude protein concentrations in the DM of the respective fractions were 70–236 (leaf blade), 35–77 (stem) and 75–120 (inflorescence) g kg−1 DM. Soluble DM (% of the total) determined after mincing accounted for 31–54% of leaf, 26–56% of stem and 20–49% of inflorescence and fractional degradation of the insoluble DM was very slow, in the ranges 0.04–0.11 (leaf), 0.03–0.05 (stem) and 0.03–0.08 (inflorescence) h−1. After 24 h of in vitro incubation, plant nitrogen content became limiting for fermentation in most instances, especially with tall fescue and paspalum. Volatile fatty acid (VFA) production appeared to be similar for leaf, stem and flower fractions, but the proportion of plant DM released as VFA after 48 h was only 7–12%, with a higher value (19%) for tall fescue. Nitrogen concentration in forage DM was not directly related to VFA yield in vitro. In conclusion, the in sacco kinetics suggested slow colonisation of all components, but especially stem, which will limit the rate of nutrient production. Effective degradability was highest for leaf but rates in vivo will depend on the speed and extent of particle size reduction by chewing during eating and ruminating. Copyright © 2005 Society of Chemical Industry

Production, characterization and applications of mouse anti-grass carp ( Ctenopharyngodon idellus) growth hormone monoclonal antibodies

Mouse anti-grass carp growth hormone (gcGH) monoclonal antibody (MAb) secretors were produced by PEG-mediated fusion of NS-1 myeloma cells and splenic B-lymphocytes of gcGH hyper-immunized mice. Positive secretors were screened by direct ELISA and cloned by limiting dilution. Three positive secretors, 21D3, 22G5 and 23B3, were obtained in a single fusion trial. Anti-gcGH MAbs were produced by growing hybridomas in the peritoneal cavity of pristane-primed mouse. The three MAbs were isotyped to be IgG2a, IgG2b and IgM, respectively. IgG MAbs were purified from ascitic fluid by Hitrap protein G column and IgM MAb was purified by gel filtration chromatography. The purified MAbs were highly specific and had moderate binding affinity. The MAbs were successfully used for the purification of native gcGH from mature grass carp pituitary extract by one-step immunoaffinity chromatography, for the quantification of gcGH by competitive sandwich ELISA, and for the probing of somatotropes in grass carp pituitary by immunohistochemistry.

Effectiveness of new agri-environment schemes in providing foraging resources for bumblebees in intensively farmed landscapes

Intensive farming has contributed to the serious declines in abundance and geographic range suffered by several bumblebee species in Europe and North America. Recent UK agri-environmental policy aims to conserve and restore bumblebee populations by providing foraging habitats on arable field margins. We examined the effectiveness of strategies to achieve this, including sowing seed mixtures of (1) tussocky grass species, (2) wildflowers and (3) pollen- and nectar-rich plants. These were compared to conventionally managed cereal crops. Sampling was undertaken in 32 10 × 10 km squares throughout England, each containing a sample of the different field margin types. Bumblebee abundance in July and August was significantly higher on pollen and nectar margins (86 ± 14 bees per 100 m) compared with wildflower margins (43 ± 14), mature grass margins (6 ± 14) and recently sown grass margins (8 ± 4). Bees were virtually absent from the cereal crop (0.2 ± 0.1). Bumblebee species richness was significantly higher on margins sown with either wildflowers or the pollen and nectar mix. There was evidence that richness of the bumblebee assemblage at the 10 × 10 km square scale was positively correlated with land use heterogeneity, the proportion of grassland, and the abundance and richness of dicotyledon flowers. The abundance of long-tongued bees per margin was explained by the number of pollen and nectar agreements per 10 × 10 km square, together with flower abundance. Future research is required to determine the quantity and location of foraging habitat required to sustain bumblebee populations at the landscape scale.

Effect of Initial Harvest Timing on Cultivar Yield in Cool‐Season Forage Grass Trials

Cool‐season forage grasses have a range of inter‐ and intraspecies heading dates in the spring. Selecting a manageable harvest schedule that does not confound yield estimates through a harvest × maturity interaction is troublesome in forage variety trials. Our objective was to determine the extent of interaction between cool‐season forage grass maturity and initial spring harvest when estimating total season yield. Cultivars of orchardgrass (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), smooth bromegrass (Bromus inermis Leyss.), tall fescue (Festuca arundinacea Schreb.), and timothy (Phleum pratense L.) differing in relative maturity were established in silt loam soils in 1997 and 1999 at Rock Springs, PA. Orchardgrass and perennial ryegrass were established at the same site in 2001. After the seeding year, three harvest schedules resulting in four harvests per year were applied: (A) each individual cultivar was harvested when it reached boot stage (R0 stage); (B) all cultivars within a species were harvested when the average cultivar maturity within that species was at boot stage; and (C) all cultivars of all species were harvested when the average maturity of all species/cultivars was at boot stage. Subsequent harvests were taken at 35‐d intervals. There was no cultivar × harvest schedule interaction for dry matter (DM) yields in this research. Tall fescue (12140 kg ha−1 yr−1) was the highest‐yielding and perennial ryegrass (5316 kg ha−1 yr−1) the lowest‐yielding species. Cultivars within each species differed in DM yield. Delaying orchardgrass or smooth bromegrass harvest beyond the boot stage (Harvest Schedule C) resulted in increased yields. The results of this research indicate that timing of initial harvest has no effect on relative cultivar total‐season yield within the species tested.

Mulberry-Fruit-Based Feed Blocks

Chitral is an isolated mountainous tract of 14,850 km2 in the northernmost part of Pakistan, bordering on Afghanistan to the north and west, and surrounded by the high ranges of the Hindu Kush and Karakoram. As only about 18% of Chitral is cultivable, its people are heavily dependent on livestock for their livelihood. Generally, livestock in the area are undernourished owing to the diminishing supply of feed on deteriorating rangelands. Local livestock feed resources in Chitral include grazing (78.1%), crop residues (20.76%), fodder crops (0.81%), and cereal bran (0.32%). Fluctuating nutrient supply caused by extreme weather conditions has considerably reduced livestock productivity. Feed is scarce during the long winters extending from November to April, during which animals subsist entirely on stall-feeding consisting of mature grass, hay, and crop residues. Concentrate supplements are expensive and not affordable by poor farmers. Molasses-urea blocks, although highly relevant to the feed situation in Chitral as a strategic supplement, cannot be prepared locally due to unavailability of molasses in the area. High transportation costs for molasses and feed blocks from plains areas are additional prohibitive factors. The present study explores the use of mulberry fruit, abundantly available in Chitral (Figure 1), to make solidified multinutrient feed blocks.

Influência das adubações nitrogenada e fosfatada sobre a composição químico-bromatológica do capim Marandu (Brachiaria brizantha (Hochst) Stapf cv. Marandu)

The carried out to estimate the effect of nitrogen and phosphorus’ fertilization on the crude protein (CP) content, neutral detergent fiber (NDF), acid detergent fiber (ADF), dry matter digestibility (IVDMD), and phosphorus’ content in dry matter of Marandu grass (Brachiaria brizantha Stapf cv. Marandu) in summer period (SP) and winter period (WP), under crescent levels of nitrogen (0; 200; 400; 600kgha-1) and phosphorus’ fertilization (0; 50; 100; 150; 200kgha-1). The CP and P content showed a increase by crescent levels of nitrogen (P < 0.05), with a linear effect and a quadratic response, respectively, at SP. However, the NDF showed a decrease in two periods (P < 0.05), and at RP it showed an association effect of nitrogen/phosphorus, and a linear effect by crescent levels of nitrogen at WP. The ADF showed a linear decrease at SP and WP, by crescent levels of nitrogen. The nitrogen and phosphorus’ fertilization did not make better the IVDMD, however, there was a lower decrease at FDA, FDN.

Impact of Forage Legume Hays Derived from Intercrop as Dry Season Feed Supplements for Lactating Bunaji Cows and N'dama Beef Cattle

Akinlade, J.A., Smith, J.W., Larbi, A., Adekunle, I.O., Taiwo, A.A. and Busari, A.A. 2003. Impact of forage legume hays derived from intercrop as dry season feed supplements for lactating Bunaji cows and N'dama beef cattle. J. Appl. Anim. Res., 24: 185–191. Two experiments were conducted concurrently to study the influence of three forage legume, hays (Stylosanthes guianensis, Centrosema pubescens and Cajanus cajan) obtained from maize—based intercropping system, as supplements to mature guinea grass (Panicum maximum). The legume hays were fed to lactating Bunaji cows (Experiment 1) and N'dama calves (experiment 2) for a period of 30 and 60 days, respectively using a completely randomized design with 4 animals per treatment in both trials. The dry matter degradation characteristics of the forage legumes were also assessed in three rumen—fistulated Bunaji castrates. Cows supplemented with C. pubescens and C. cajan produced higher milk (P<0.05) than those offered S. guianensis. Calves supplemented with C. pubescens and S. guianensis gained more weight (P<0.05) than those fed on C. cajan—supplement. Degradable fraction (b) were 338, 334 and 470g/kg for S. guianensis, C. pubesces and C. cajan, respectively. Additional benefits in terms of higher milk and body weight increase could be derived from the use of cereal-based inter-cropped forage legumes as supplements especially by poor resource African smallholder mixed farmers in the dry season.

Productivity and nutritive value of some cultivated perennial grasses and mixtures in the alpine region of the Tibetan Plateau

AbstractThe productivity and nutritive value of some cultivated perennial grasses, Bromus inermis (B), Elymus sibricus (S), E. nutans (N), Agropyron cristatum (A), Poa crymophila (P) and mixtures B + N, S + A, B + S + A, S + B + N, N + S + A, B + S + N + A, B + N + A + P, B + S +A + P and S + N + A + P, in the alpine region of the Tibetan Plateau were investigated. Elymus nutans and E. sibricus and the mixtures, B + S + N + A, B + S +A + P and S + N + A + P, were most productive with yields of dry matter (DM) of between 11 000 and 14 000 kg−1 of biomass annually in the second harvest year. Acid‐detergent fibre (ADF) concentrations increased (P &lt; 0·05), and crude protein (CP) concentrations and in sacco DM degradability values decreased (P &lt; 0·05) with the maturity of the cultivated grasses. Swards, based on these species and mixtures, have the potential to be the main choices for cultivation in the Tibetan Plateau because they produce more nutrients than other grass species and mixtures. Late August (flowering stage of dominant grasses) is the optimum time for harvesting as the yield of rumen‐degradable CP is highest that of DM relatively high and the DM degradability is satisfactory.

Water use and water-use efficiency of the invasive Centaurea maculosa and three native grasses

The Eurasian herb Centaurea maculosa Lam. has invaded millions of hectares of semi-arid grasslands in western North America. Its success may reflect that it may be more competitive than native species, it is not grazed by large herbivores, it was introduced without its native enemies, it may interfere with native species via allelopathy, or most likely some combination of these factors. Greater competitive ability could include greater use of limiting soil resources, such as water, or more efficient use of soil water, thereby inhibiting establishment, survival, and reproduction of native species. We measured water use and water-use efficiency of Centaurea and three native grasses, Pseudoroegneria spicata [Scribn. and Smith] A. Love, Pascopyrum smithii [Rybd.] A. Love, and Festuca idahoensis Elmer, in a glasshouse. Water-use efficiency was determined by the traditional measure of biomass produced per mass of water used, and by carbon-isotope discrimination (Δ). Centaurea did not use the most water, or use water more efficiently (based on biomass (g)/ water (kg) and carbon-isotope discrimination) than all three native grasses. We also determined carbon-isotope discrimination of Centaurea and dominant native grasses during the 1999 and 2000 growing seasons at three field sites. Centaurea rosettes had the lowest water-use efficiency (greatest carbon-isotope discrimination), followed by mature plants of Centaurea, and then native grasses. Water-use efficiency of mature Centaurea plants and native grasses was greater in late summer than early summer. Centaurea's success as an invasive species in North America cannot be attributed to greater use of soil water or greater water-use efficiency than native grasses.

Effects of a stay‐green trait on the concentrations and stability of fatty acids in perennial ryegrass

Abstract Three experiments were conducted to evaluate the effect of a stay‐green trait in perennial ryegrass (Lolium perenne) on concentrations of fatty acids as well as their susceptibility to peroxidation during wilting and to biohydrogenation by rumen bacteria. Fatty acid concentrations were recorded in stay‐green and corresponding normal perennial ryegrass selection lines over eight cuts during 1998. There was a progressive increase in total fatty acid concentrations [from 20·8 to 34·6 g kg−1 dry matter (DM)] and the proportion of fatty acids as α‐linolenic acid (from 0·62 to 0·70 g g−1) from early to late season. A second study compared fatty acid concentrations in stay‐green and normal herbage that was wilted for up to 48 h. There was a loss of 0·2–0·3 g g−1 fatty acids during 48 h of wilting and a small reduction in the rate of loss of α‐linolenic acid in stay‐green perennial ryegrass compared with normal herbage (0·223 vs. 0·290 g g−1 lost after 48 h). Stay‐green and normal perennial ryegrasses were offered to grazing lambs in a third study. Higher concentrations of trans‐vaccenic acid and conjugated linoleic acid in plasma from lambs offered less mature grass in the pre‐experimental period than during the experiment are considered to reflect a greater supply of precursor (linoleic acid). There were higher concentrations of conjugated linoleic (0·0070 vs. 0·0039 g l−1) and linoleic (0·092 vs. 0·070 g l−1) acids, without an increase in trans‐vaccenic acid, in plasma from lambs grazing stay‐green perennial ryegrass than normal perennial ryegrass. This suggests that the stay‐green trait affected the rate of degradation of fatty acids in the rumen. These results demonstrate the potential for obtaining proportionately large differences in fatty acid profiles of ruminant products by altering grassland management.

Grass composition and rangeland condition of the major grazing areas in the mid Rift Valley, Ethiopia

A range inventory and condition study was conducted in three altitude zones: lowland (1500-1700m), medium altitude (1700-2000m), and highland (2000-2500m). Each altitude zone was stratified into four or five important grazing areas. One area represented lightly grazed government ranches or parks which were used as benchmarks, another area represented the seasonal grazing areas with an intermediate grazing pressure and the remaining were the heavily grazed roadsides, lakeshores and other communal grazing lands. The range condition assessment was based on the composition of the herbaceous layer, basal cover, litter cover, relative number of seedlings, age distribution of grasses, soil erosion and soil compaction. Dry matter was sampled in the mid-wet season to assess the relationship between available dry matter and range condition. A total of 36 grass species, 3 legume species, 2 sedge species, 15 other herbs and 31 species of trees were identified. The palatable Cenchrus ciliaris was dominant in the benchmarks and seasonally grazed areas of the lowland while Hyparrhenia spp. dominated in the same areas of the medium altitude. Cynodon dactylon, and the non-palatable Eleusine floccifolia and Pennisetum schimperi were dominant on heavily grazed areas of the lowland, medium altitude and highland, respectively. The total score for range condition of the benchmarks (34 out of 50 points), was significantly higher than that of the seasonally grazed areas (26), the heavily grazed communal grazing areas (19), roadsides (16) and lakeshores (17) (P<0.05). The highlands showed a higher score for benchmarks and seasonally grazed areas only. There was a significant linear relationship between available dry matter of grasses and range condition (excluding unpalatable pioneer grasses, r2 = 0.56, P<0.01). Seasonally grazed areas were identified as key sites for pasture improvement since these are privately owned and managed. Pasture improvement will reduce the grazing pressure on the heavily grazed roadsides, lakeshores and other communally grazed areas.

Effects of stage of maturity and chop length on the release of cell contents of fresh ryegrass (Lolium perenne L.) during ingestive mastication in steers fed indoors

The objective of the trial was to analyse the effects of the mechanical resistance of cell walls and chewing behaviour on the proportion of intracellular constituents (ICs) released during the ingestive mastication of fresh perennial ryegrass (Lolium perenne L.) by steers. The mechanical resis- tance of cell walls was varied by the stage of maturity (15 vs. 30 days of regrowth). Herbage was of- fered at two chop lengths (long and short) for each stage of maturity, to influence chewing behaviour. Four steers, each fitted with a large ruminal cannula, were fed indoors with the ryegrass in a 4 × 4 Latin square design. Ingested boli were collected at the cardia and their IC contents were compared with the IC contents of the grass. The average shear energy was lower with the young grass because of a lower proportion of stems and pseudostems. The eating time per unit of dry matter intake was unaf- fected by the stage of maturity, but was slightly lower with the short herbages. The nature of the ICs had a strong effect on their release with the larger molecules, or the molecules contained in the chloroplasts, being less rapidly released. The ICs released (as a proportion of intake) ranged from 0.166 for the chlorophyll to 0.612 for the nitrates. The treatments had no effect on the rate of release of the small vacuolar or cytoplasmic ICs. The intracellular nitrogenous fractions, partly in the chloroplast, were released faster in the mature grass, because the animals had to masticate more inten- sively to obtain a 'swallowable'bolus due to it having a higher shear energy. The release of ICs did not seem to be dependent on the duration of chewing but rather on other parameters of mastication like the force exerted by the jaws, the surface-area of the molars, or the quantity of grass eaten per bolus. rumen digestion / water soluble carbohydrates / nitrogenous compounds / mastication / shear strength