Modelling Tiller Density Dynamics in a Grass Sward

Simulation models are useful tools for grassland management. Among many quantitative and qualitative attributes describing vegetation of grasslands, density of plant population is important because of its close relationship with persistence of grasslands (Hirata, 2004), which in turn is crucial for sustainable agricultural production and/or conservation of the environment, wildlife and recreational resource. Although various models have described grassland vegetation, relatively few models have dealt with plant population density. This paper presents a model describing dynamics in tiller population density in a grass sward

The Effect of Herbage Mass of a Pasture on the Spatially Heterogeneous Grazing by Cattle

To obtain information on spatially heterogeneous grazing by large herbivores at different time scales, spatial distribution of herbage mass and rate of defoliation was investigated on a bahiagrass (Paspalum notatum Flügge) pasture grazed by cattle during 4 to 5-day grazing periods in May, August and October. Pre-grazing herbage mass (Mpre) showed decreasing mean values and increasing spatial heterogeneity with the progress of grazing in all grazing periods, while the rate of defoliation showed inconsistent changes with season. Spatial distribution of the rate of defoliation was always more heterogeneous than that of Mpre. The correlation coefficient between Mpre and rate of defoliation increased with decreasing mean Mpre on the seasonal basis. The same trends also appeared with the daily progress of grazing in August and October. However, in May when the mean Mpre was less than 40 g DM/2500 cm2, the correlation remained almost constant at significant levels. It was shown that cattle consumed more herbage from locations with greater Mpre as the mean Mpre of the pasture decreased to the critical amount (40 g DM/2500 cm2), but they did not increase their selectivity for higher Mpre locations when the mean Mpre fell below the critical amount

Long-term Trend in Pre-grazing Horizontal Distribution of Herbage Mass in Bahiagrass Pasture (Paspalum notatum Flügge)

Grazing by cattle plays a main role in development of spatial heterogeneity in pasture and through it, as well, in stability of particular grazing system. In this study the first five years (1995-1999) of a long-term trial in pre-grazing distribution of herbage mass in bahiagrass pasture, utilised under the same repeated grazing management are shown. Herbage mass was non-destructively estimated with an electronic capacitance probe at 182, 50 by 50 cm locations along 2 permanent line transects. The changes in pre-grazing horizontal distribution of herbage mass during five grazing seasons were measured always on the same position on two transects just before the beginning of each grazing period (27 occasions). The pre-grazing herbage mass shows spatially heterogeneous distribution, as it was indicated by the coefficient of variation in the range from 0.221 (August 1998) to 1.107 (September 1995) for all measurement dates. This research had also the aim to quantify the stability of sward in a long-term distribution of pre-grazing herbage mass in bahiagrass pasture, and the calculated correlation coefficient of multilinear regression (r=0.612) was highly significant (p 0.001). Anyway, it is difficult to say weather this pasture is going to maintain the same spatial pattern of herbage mass in, for example, next five years. That is, to continue this research in the future is necessary task in obtaining more information about spatial heterogeneity of vegetation in bahiagrass pasture, and implication of agro ecological advantages to grazing systems

The Effect of Progressive Grazing of a Pasture on the Spatial Distribution of Herbage Mass and Utilization by Cattle

To develop an understanding of the spatially heterogeneous grazing of a pasture by large herbivores under progressive grazing, the herbage mass, herbage consumption and ingestive behavior by cattle were monitored daily at ninety-one 50 × 50 cm permanent locations in a bahiagrass (Paspalum notatum Flügge) pasture during a 6-day grazing period. With the progress of grazing, the mean pre-grazing herbage mass over the locations decreased. Responding to this, the mean number of visits and the mean rate of biting increased, and the mean residence time and the mean rate of defoliation decreased. The pre-grazing herbage mass became more heterogeneous, whereas the number of visits and the rate of defoliation became more homogeneous, based on the coefficient of variation. The overall spatial heterogeneity was ranked: rate of defoliation \u3e number of visits ≥ residence time ≥ pre-grazing herbage mass \u3e rate of biting. The results have provided some new information about the spatially heterogeneous grazing by cattle in a monospecific grass pasture, though further analyses and studies are necessary for fully understanding the mechanisms behind the diverse responses of the spatial heterogeneity of the variables to grazing

Relationships between Spatial Distributions of Herbage Mass and Utilization in a Pasture Progressively Grazed by Cattle

To obtain some information about the mechanisms behind the spatially heterogeneous grazing of a pasture by large herbivores, the relationships between the spatial distributions of herbage mass, herbage consumption and ingestive behavior were investigated on a bahiagrass (Paspalum notatum Flügge) pasture during a 6-day grazing period with cattle. The animals almost always consumed more herbage from locations with higher pre-grazing herbage masses, which was attributed to greater bite weights. It was suggested that the high spatial heterogeneity in the rate of defoliation was caused mainly by the spatial heterogeneity in both the bite weight and the number of visits when the mean pre-grazing herbage mass of the pasture was relatively high, and by the spatial heterogeneity in the bite weight when the mean pre-grazing herbage mass was relatively low

Two-Dimensional Monitoring of Spatial Distribution of Herbage Mass under Grazing

Spatial distribution of herbage mass (HM) was monitored two-dimensionally during the grazing season (from May to November) in a bahiagrass pasture rotationally grazed by cattle. An electronic capacitance probe was used to estimate HM in 1464 permanent positions (50 × 50 cm) whose centres formed 1.5 × 1.5 m grids in the central 90 × 34.5 m area of the pasture. The highest mean HM was in September and October, while coefficient of variation in November. The two-dimensional charting of HM showed almost stable spatial patterns throughout the grazing season, with some patches of high HM appearing and disappearing. The development of new patches was considered to be partly due to the avoidance of areas affected by newly deposited dung pats, and the extinction of patches to the grazing down of areas where dung pats were disappearing or had disappeared. It was concluded that the technique is useful for monitoring the spatial pattern of HM, herbage production and consumption, and for associating the consumption with ingestive behavior of grazing animals

Leaf and Tiller Dynamics in Centipede Grass and Bahia Grass

Centipede grass (Eremochloa ophiuroides (Munro) Hack.) is a warm-season perennial which has received the attention of farmers and researchers as a new forage resource for sown pastures in the low-altitude regions of south-western Japan where bahia grass (Paspalum notatum Flügge) has been widely used (Islam & Hirata, 2005). Leaf and tiller dynamics provide the basis to explain variation in production and canopy structure of a grass sward (Rhodes & Collins, 1993), and knowledge of the dynamics can be used as a tool for sward management. However, this information is lacking for centipede grass (Islam & Hirata, 2005). The aim of this study was to obtain information on leaf and tiller dynamics of centipede grass in comparison with bahia grass

Management Options that Increase Herbage Production in Grassland-Based Livestock Production Systems

Herbage production is the most important measure of performance of grassland systems. Understanding how herbage production responds to various managements is crucial to the success of grassland systems, whether or not maximization of production is pursued. Most of the records of grassland production in the literature are taken as acceptable approximations of net herbage production. Analysis of these production records and accompanying quality data can generalize the response of grassland productivity and quality to individual managements, and can characterize the managements in terms of their efficiency and potential in increasing productivity and quality. Overall, maximum production response is ranked irrigation (11.2 t DM/ha) \u3e nitrogen (N) fertilizer (9.8 t DM/ha) \u3e legume mixture (5.2 t DM/ha) \u3e phosphorus fertilizer (3.4 t DM/ha) \u3e cutting frequency (2.5 t DM/ha) ≈ potassium fertilizer (2.4 t DM/ha) \u3e cutting intensity (1.9 t DM/ha). Maximum response of herbage N concentration is greatest for N fertilizer (16 g/kg DM, for grasses) followed by legume mixture (14 g/kg DM), cutting frequency (8 g/kg DM) and cutting intensity (2 g/kg DM). Management of grassland systems for achieving a specified production and/or quality goal needs to consider different patterns of production and quality response to individual management inputs as well as other conditions (e.g. plant species, site conditions) involved in the systems

PLASMA CELL INFILTRATION AND MUCOID DEGENERATION IN THE MEDIA OF ASCENDING AORTA IN PATIENT WITH CORONARY ARTERY DISEASE

Aims Atherosclerosis results in inflammatory changes in the aortic intima， but little is known regarding medial changes. Atherosclerosis of the ascending aorta coexists with coronary artery disease. The aim of this study was to investigate the atherosclerotic changes in 44 biopsy specimens of media of the ascending aorta associated with coronary artery disease. Plasma cells do not appear in non-inflammatory tissue. Methods We compared plasma cells，and matrix metalloproteinase (MMP)-2-，-9- and -12-positive cells immunohistochemically，and we also compared mucoid degeneration and fibrosis determined by staining using a point-counting method，for groups with a variable number of coronary stenotic (≧75%)lesions. Results In patients with one to three coronary stenotic lesions，plasma cells and mucoid degeneration were low in the aortic media. With four to five lesions，bo th plasma cells and mucoid degeneration increased significantly compared with those in the group with one to three lesions，and MMP-12-positive cells significantly decreased. In patients with six to nine lesions，the number of plasma cells was significantly lower than in patients with four or five lesions，whereas mucoid degeneration significantly increased. There was no change in fibrosis. Conclusions These findings may help us to better understand and treat atherosclerosis