Ecophysiology and Management Response of the Subtropical Grasslands of Southern South America

The subtropical grasslands of Southern South America (campos) are located approximately in the range of 24° S to 37° S latitude. These grasslands are dominated by C3 and C4 grasses, and in a lesser extent to herbaceous plants, shrubs and dispersed trees, with some exceptions in particular regions. Previous to the introduction of large herbivores, at the beginning of the XVII century, like cattle and horses, shrubs and tall grasses dominated the vegetation. Then, associated with greater grazing pressure and partially due to fire, the original campos are maintained, actually in a pseudo-climax herbaceous phase. These native communities are highly stable, adapted to long periods of water stress and flooding. Campos are generally grazed at continuos stocking all year around by sheep, cattle and horses. With the exceptions of the secondary plant successions, the summer growing species (C4) dominate the campos vegetation, having a high relative frequency (75%). Continuos grazing and coarse summer grasses contribute to decrease the frequency of winter species (C3). There is a high spatial and temporal variation in the native communities related to the type of soil, texture, water capacity, topography, altitude, management, etc., which determinate the different proportions of vegetation types and botanical compositions. The temporal variation is mainly associated with climatic factors, principally rainfall, affecting the variability of the annual dry matter production of campos vegetation (CV = 40 to 50%). The range of annual forage production of campos vegetation varies between 2.5 (shallow and low fertility soils) to 7.0 ton DM ha-1 (deep and fertile soils). Most of the annual forage production is mainly concentrated in spring and summer, reaching 70-80% and 60-70% in shallow and deep soils, respectively. Grazing management, and particularly the stocking rate utilised, is the principal factor determining changes in the botanical composition in this type of vegetation. In general, the use stocking rates greater than 1 stock unit ha-1, for longer periods, causes reductions in forage production, associated with increases and decreases in the frequency of productive species and weeds/shrubs/forbs, respectively. Pasture degradation is even greater, when high stocking rates are applied in conjunction with the use of high sheep/cattle ratios (e.g. 5:1). The use of rotational grazing systems enhances pasture production by 12% as well as pasture utilisation. When continuos stocking is applied, it is difficult to achieve pasture utilisation greater than 50%. Avoiding overgrazing in degraded vegetation, it is possible to obtain a recovery in pasture conditions, while the degradation caused by continuous cropping is unrecoverable. Animal production is negatively affected when herbage mass or sward height are lower than 1000 kg DM ha-1 or 5-6 cm, respectively. Animal selectivity allows sheep and cattle to have a greater crude protein (33 and 22% respectively) and metabolisable energy (15 and 11% respectively) levels than those obtained in the pasture offered. The use application of low quantities of nitrogen and phosphate on native vegetation increase forage production and nutritive value by 50%, enhancing the contribution of winter species (C3) in the sward. Legume introduction by overseeding increases native pasture production by 60-100% and pasture nutritive value by 50-100%, particularly during winter. This response is associated with the contribution of the introduced species and additionally by the increments in proportions of the native winter species (C3), resulting in a higher plan community biodiversity. Improved pastures permit to obtain 4 to 5 times greater secondary production than those unimproved. The generated scientific knowledge has contributed to apply better pasture management practices, which resulted in biological and economical benefits to the farmer community and the whole society in the longer time, with special care of animal and plant communities biodiversity and water conservation for human and animal use. Both animals and plants will be for a long time our main source of food and fibre in the world, hence conditioning our actions and behaviour in the manner that we conserve our natural resources for the future generations

Productivity and Composition of Two Improved Native Pastures under Different Grazing Managements in Uruguay

Two improved native pastures were established by phosphoric (P) fertilisation and oversowing of: white clover (Trifolium repens) mixed with birdsfoot trefoil (Lotus corniculatus) (TbL) and annual lotus (Lotus subbiflorus) (Rin). Such pastures were evaluated during 5 years with steers at two stocking rates (High and Low) and two grazing managements (Rotational and Alternate). Presence of legumes was high and botanical changes were favourable in both pastures that evidenced good persistence. Daily liveweight gains of steers and total animal production were high in both pastures, but significantly (P≤ 0.05) higher in TbL. No significant differences were found due to grazing management. High stocking rate resulted in superior (P≤ 0.05) animal production per hectare than Low. No significant interactions were detected

Effect of Winter Grazing Management of Stockpiled Native Pastures of Basaltic Soils of Uruguay on Daily Gains of Heifers

The effect of three grazing systems of fall stockpiled native pastures on the winter gains of 66 Hereford heifers (135 kg) was studied. Treatments were: continuos grazing (CG); (C7) the plot was divided in 12 and each was grazed for 7 days and (C28), the plot was divided in 3 and each were grazed for 28 days. Heifers were weighed every 14 days and grazing behaviour was recorded. Stockpiled HM was greater (P\u3c 0.05) in C7 and C28 than in CG (988, 912, and 604 kg DM/ha, respectively). Herbage allowance (HA) was greater (P\u3c 0.01) in CG followed by C28 and C7 (11.7, 6.6 and 5.9 kg DM/100 kg LW, respectively). Post-grazing HM was greater (P0.05) in all pastures (CP 10.2%, NDF 71.2%, ADF 41.3% and ash 14.4%). Final LW of heifers were similar (P\u3e 0.05) (167, 162 and 160 kg for CG, C7 and C28, respectively). A very mild winter favoured exceptional gains which tended to be higher in CG (0.353 kg/day) than in C7 (0.305 kg/day) and C28 (0.278 kg/day). Grazing time was greater (P\u3c 0.05) in CG and bite rate was lower in C28 than in C7 and CG heifers. Grazing management did not affect daily gains. Nevertheless, total remaining HM in C28 and more so in C7 more than doubled that in CG, where more animals could have grazed with increasing total productivity

A Sheep and Catlle Diet Selection Study on a Fertilized Native Sward in Uruguay

This study was undertaken during winter, spring and summer 1997, located in the basaltic region of Uruguay to evaluate the effects of stocking rate (SR) and N and P fertilizer application on sward characteristics and on sheep and cattle diet selection and grazing behaviour. The treatments applied were: a) control (C; without fertilizer application using a SR of 0.9 stock units (SU)/ha), b) T1 (with N and P fertilizer application using a SR of 0.9 SU/ha), c) T2 (with N and P fertilizer application using a SR of 1.2 SU/ha) and d) T3 (with N and P fertilizer application using a SR of 1.5 SU/ha). In general, compared with C, fertilized treatments resulted in increments in sward surface height (SSH) and sheep bite weight (BW): a) winter (3, 8, 5 and 5 cm., P \u3c 0.01; 79, 142, 139 and 92 mg DM/bite, P \u3c 0.05), b) spring (3, 8, 5 and 6 cm., P \u3c 0.01; 108, 188, 115 and 215 mg DM/bite, P \u3c 0.01), and c) summer (7, 14, 11 and 8 cm., P \u3c 0.01;146, 199, 182 and 131 mg DM/bite, P \u3c 0.05) for C, T1, T2 and T3, respectively. In general, the nutritive value of diet selected by sheep and cattle was higher than that of the pasture on offer, and higher in sheep than in cattle: a) winter (17, 18 and 16% crude protein, CP, P \u3c 0.05; 39, 37 and 41% acid detergent fiber, ADF, P \u3c 0.05), b) spring (11, 14 and 11% CP, P \u3c 0.05; 42, 33 and 37% ADF, P \u3c 0.01), and c) summer (8, 10 and 9% CP, P \u3c 0.05; 50, 40 and 45% ADF, P \u3c 0.01) for pasture on offer, sheep and cattle diets, respectively. This study demonstrated the importance of fertilizing native swards to improve production, structure, nutritive value, and animal carrying capacity and animal performance. It also shows the important role that diet selection plays in determining the nutritive value of the forage eaten by sheep and cattle, and stresses the greater selective ability of sheep over cattle

A Comparative Grazing Study of Sheep and Cattle Diet Selection on Native Pastures in Uruguay

An experiment was carried out during winter, spring and summer 1997, on native pastures of the basaltic region of Uruguay to evaluate the effects of different herbage mass levels (high, medium and low) on sward characteristics and on sheep and cattle diet selection and grazing behaviour. Higher herbage masses resulted in increments in herbage accumulation and sheep bite weight: winter (1880, 1513 and 610 kg DM ha-1, P \u3c 0.01; 199, 148 and 128 mg DM/bite, P \u3c 0.01), and summer (3046, 2175 and 1172 kg DM ha-1, P \u3c 0.01; 214, 175 and 143 mg DM/bite, P \u3c 0.01) for high, medium and low herbage mass levels respectively. The nutritive value of diet selected by sheep and cattle was higher than that of the herbage on offer, and higher in sheep than in cattle: winter (10.2, 15.9 and 12.5% crude protein, CP, P \u3c 0.05; 49.2, 32.4 and 38.1% acid detergent fiber, ADF, P \u3c 0.01, and summer (7.4, 10 and 9.5% CP, P \u3c 0.05; 51.1, 36.8 and 43% ADF, P \u3c 0.01) for herbage on offer, sheep and cattle diets respectively. These contrasting results found in the nutritive value were closely associated with differences in the proportions of the botanical components recorded, particularly the differential contribution of dead material. This experiment quantified the importance of diet selection in determining the nutritive value of the forage eaten by sheep and cattle on the native pastures of the basaltic region of Uruguay and established some relationships between diet selection and grazing management, involving animal selectivity ability differences (sheep versus cattle) and seasonal effects

Effect of Stocking Rate and Grazing System on Fine and Superfine Merino Wool Production and Quality on Native Swards of Uruguay

Modern textile tendencies show that consumers prefer light, soft, resistant, natural, and comfortable clothes, for which fine and superfine wools are in great demand, particularly at the high value markets (Whiteley, 2003). The main objective of the present study was to define sustainable stocking rates and grazing systems on native swards for fine and superfine wool production in the Basaltic region of Uruguay

Mixed Fattening of Steers and Lambs on Improved Grasslands in Uruguay: II. Animal Performance and Productivity

In cow-calf operations in Uruguay, mixed cattle and sheep grazing on rangelands is predominant, while fattening is a specialised process. Within certain limits of the lamb/steer ratio and stocking rate, a complementary grazing effect occurs under mixed grazing, improving net results (Nolan & Connolly, 1977; Risso et al., 2002). These trials characterise animal performance under such management

Mixed Fattening of Steers and Lambs on Improved Grasslands in Uruguay: I. Pasture Performance

The use of P fertilisers together with legume broadcasting is a low cost and high impact technology for improving native grassland (Risso et al., 2001). Its use is increasing in Uruguay, although not for mixed grazing, even though this management is a common practice on native grasslands. Good pasture response may occur under mixed grazing when it is adequately managed (Nolan & Connolly, 1989). The following trials characterise pasture response with such management, in Uruguayan conditions

Amphetamine-evoked c- fos mRNA expression in the caudate-putamen: the effects of DA and NMDA receptor antagonists vary as a function of neuronal phenotype and environmental context

Dopamine (DA) and glutamate neurotransmission is thought to be critical for psychostimulant drugs to induce immediate early genes (IEGs) in the caudate-putamen (CPu). We report here, however, that the ability of DA and glutamate NMDA receptor antagonists to attenuate amphetamine-evoked c- fos mRNA expression in the CPu depends on environmental context. When given in the home cage, amphetamine induced c- fos mRNA expression predominately in preprodynorphin and preprotachykinin mRNA-containing neurons (Dyn-SP+ cells) in the CPu. In this condition, all of the D1R, D2R and NMDAR antagonists tested dose-dependently decreased c- fos expression in Dyn-SP+ cells. When given in a novel environment, amphetamine induced c- fos mRNA in both Dyn-SP+ and preproenkephalin mRNA-containing neurons (Enk+ cells). In this condition, D1R and non-selective NMDAR antagonists dose-dependently decreased c- fos expression in Dyn-SP+ cells, but neither D2R nor NR2B-selective NMDAR antagonists had no effect. Furthermore, amphetamine-evoked c- fos expression in Enk+ cells was most sensitive to DAR and NMDAR antagonism; the lowest dose of every antagonist tested significantly decreased c- fos expression only in these cells. Finally, novelty-stress also induced c- fos expression in both Dyn-SP+ and Enk+ cells, and this was relatively resistant to all but D1R antagonists. We suggest that the mechanism(s) by which amphetamine evokes c- fos expression in the CPu varies depending on the stimulus (amphetamine vs. stress), the striatal cell population engaged (Dyn-SP+ vs. Enk+ cells), and environmental context (home vs. novel cage).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66272/1/j.1471-4159.2003.01815.x.pd

QAPgrid: A Two Level QAP-Based Approach for Large-Scale Data Analysis and Visualization

Background: The visualization of large volumes of data is a computationally challenging task that often promises rewarding new insights. There is great potential in the application of new algorithms and models from combinatorial optimisation. Datasets often contain “hidden regularities” and a combined identification and visualization method should reveal these structures and present them in a way that helps analysis. While several methodologies exist, including those that use non-linear optimization algorithms, severe limitations exist even when working with only a few hundred objects. Methodology/Principal Findings: We present a new data visualization approach (QAPgrid) that reveals patterns of similarities and differences in large datasets of objects for which a similarity measure can be computed. Objects are assigned to positions on an underlying square grid in a two-dimensional space. We use the Quadratic Assignment Problem (QAP) as a mathematical model to provide an objective function for assignment of objects to positions on the grid. We employ a Memetic Algorithm (a powerful metaheuristic) to tackle the large instances of this NP-hard combinatorial optimization problem, and we show its performance on the visualization of real data sets. Conclusions/Significance: Overall, the results show that QAPgrid algorithm is able to produce a layout that represents the relationships between objects in the data set. Furthermore, it also represents the relationships between clusters that are feed into the algorithm. We apply the QAPgrid on the 84 Indo-European languages instance, producing a near-optimal layout. Next, we produce a layout of 470 world universities with an observed high degree of correlation with the score used by the Academic Ranking of World Universities compiled in the The Shanghai Jiao Tong University Academic Ranking of World Universities without the need of an ad hoc weighting of attributes. Finally, our Gene Ontology-based study on Saccharomyces cerevisiae fully demonstrates the scalability and precision of our method as a novel alternative tool for functional genomics