Super- and coinfection: filling the range

Journal ArticleHow many different strains of a disease can coexist in a single population of hosts? What effect do different mechanisms of coexistence have on the properties of diseases? The principle of competitive exclusion (Armstrong and McGehee 1980; Levin 1970) states that no more species can coexist in a system than the number of resources or limiting factors allow, which can be thought of, somewhat imprecisely, as stating that a single trade-off can support only a single species - the one that deals best with that trade-off

Agronomic Characterisation of Sewage Sludge: Residual Effects

The progressive implementation of the EU Urban Waste Water Treatment Directive 91/271/EEC is increasing the quantities of sewage sludge requiring disposal. Agronomic use of sewage sludge should be based on crop fertiliser requirements and heavy metals content. Sewage sludge fertiliser potential depends on the stabilisation treatments of sewage sludge: composting, anaerobic digestion, aerobic digestion or pelleting (EPA, 1994). The objective of this experiment was to evaluate the fertiliser effectiveness and residual effects of three types of sewage sludge treated in three different ways

Relationship Between Height and Sward Quality in Rotational Dairy Systems

Height is a good guide for management in dairy systems.Intake by dairy cows depends on amount offered and quality of pasture and for this reason a relationship between that offered and pasture quality with height should be studied. The experiment was conducted in NW of Spain with three different stocking rates in dairy systems. A lower quality sward was found in the taller offered pasture as indicated by its higher ADF and lower CP percentages. Total sward ADF (kg x ha-a) was higher in taller offered pasture, which indicated a lower pasture quality, however the total CP was positively related with the pasture height in the offered pasture interval studied. Offered pasture lower than 2500 kg/ha (a height of 17.5 cm) had higher protein content but reduced digestibility (increased the ADF) compared with lower offered pasture

Non-Destructive Methods for the Estimation of Sward Production

Two non- destructive methods of grass production were compared: grassmeter and sward stick, in order to find an equation for transforming one into the other in dairy rotational systems. Linear, logarithmic and quadratic equations were fitted to the data. Linear equation was preferred by simplicity. General equations which included all the year periods showed no differences between sward stick and grassmeter. A detailed study of the different phenology states showed lower heights with grassmeter than with the sward stick method, which should take into account grazing management height recommendations

Seasonal Variation of Crude Protein Content of Different Herbaceous, Shrub and Tree Species

Silvopastoralism is a sustainable way of land management that reduces fire risk due to the reduction of fuel under trees when plants are used as animal food. This is particularly important in areas like Galicia that have 16% of the fired area of Europe. Silvopastoral systems can contribute to environment conservation and provide feed for autochthonous breeds more adapted to mountain conditions, enhancing biodiversity conservation. In formation on seasonal changes in crude protein content of spontaneous species will indicate better management of pasture resources in mountain areas

Shading Effect on Production and Protein Concentration of \u3cem\u3eDactylis Glomerata\u3c/em\u3e and \u3cem\u3eAgrostis Tenuis\u3c/em\u3e

Silvopastoral systems make compatible livestock and timber production and provide important advantages from economic and ecological points of view (Sibbald, 1996). Around one million ha of new afforested areas promoted by the EU Common Agricultural Policy have been established in the last decade, that can be used as potential silvopastoral system areas. Pasture production is usually reduced in dense stands as trees grow up due to the light interception by the tree crown, but the radiation reaching the soil will depend on the tree type and this will affect herbaceous species composition and development. The aim of this work was to evaluate the shading effect (0 and 50 % of light interception) on pasture production and composition of monocultures of cocksfoot (Dactylis glomerata L. var. Artabro) and bent grass (Agrostis tenuis Sibth. cv Highland) in simulated conditions

Effect of Tree Species and Density on Pasture Production in Galicia, Spain

Galicia produces 50% of the forest products of Spain. Livestock production earns 62% of the income of the agrarian sector in Galicia. Afforestation has been very important in the last decade to such an extent that the area of forest and woodlands now covers 62% of Galicia. It is necessary to increase the rate of return on investments in planted forests in order to avoid rural depopulation through improvement of rural development and welfare. This paper reports on the effect of combining pastures with trees

Pasture Production After Sewage Sludge and Liming Application on Highlands in North West Spain

In recent years, a sewage sludge surplus has been created in the EU countries, due to the Urban Waste Water Treatment Directive 91/271/CEE. Therefore, it is necessary to find adequate disposal for these residues in accordance with EU policy. Organic matter and nutrient sewage sludge contain principally N, indicating that it could be used as fertiliser. The main risk of this residue is its heavy metal content, whose solubility is usually increased as soil pH declines. The objective of this experiment was to determine the effect of liming and sewage sludge application on pasture production in a silvopastoral system located on acid soi

Silvopastoral Systems: Analyses of an Alternative to Open Swards

Silvopasture is a sustainable land use management practiced in most continents in the world including parts of southern Europe, but is not broadly used in northern and western Europe. The importance of this practice has been recognised and the last draft of the EU regulation by the European Agricultural Fund for Rural Development (http://europa.eu.int/comm/agriculture/capreform/rurdevprop_en.pdf) includes specifically funding for establishment of agroforestry practices in Europe. This paper discusses the advantages of managing semi intensive grassland within a silvopastoral system from an ecological, productive and social point of view in the south, south-central and western countries of Europe