The Effects of Secondary Metabolites of Rangeland and Pasture Plants on the Animal Health in Mediterranean Ecological Conditions

Abstract

Grazed areas including rangelands and pastures cover approximately 51% of the Earth's continental surface. The plant species which are in these areas which form a wide biodiversity with living and non-living organisims, stand out with both as a forage source and medical use. In this natural habitat, plants are surrounded by a large number of potential enemies. Since plants are not able to escape from these enemies (herbivores and pathogenes), plants produce substances which are not functional for growing and develop but protect plants against external factors as defence mechanisms. These substances are called secondary metabolites. These substances which are seen differently from the primer metabolites, possess charachteristics specific to each plant species. Secondary metabolites of plant origin can be divided into three main groups as terpens, phenolic compounds and nitrogenous compounds. Terpenes have negative effects on many mammals and insects, because they are toxic. The lignin, a phenolic compound, is located in the plant cell wall and has a particularly digestibility-lowering effect. In addition, flavanoids, which are again phenolic compounds, are thought to be produced against harmful effects of UV rays and pathogen invasion. Tannins, another phenolic compounds, are generally toxic. When plants which have tannins are grazed by herbivorous, they significantly reduce chances of growth and survival of animals. Finally, the alkaloids which are in the nitrogenous secondary products, are seen in a very wide area. These metabolites, especially in invasive plants that are heavily exposed to heavy grazing rangelands and pastures, affect the nervous system in livestock and can cause paralysis and even sudden deaths These three secondary metabolite groups are also commonly found in plants that are not properly managed in the meadow and pasture areas of the Mediterranean climate zone and can cause economic damage by affecting animal health and quality of animal products, especially in areas where animal production is seen. However, these economic losses are not only due to the plant species but can change with the influence of environmental factors. Moreover, not every livestock is affected by the same damage, the damage threshold varies according to the livestock species. This situation affects the livestock sector and natural vegetation, which already have problems. If the rangelands and pastures we call quality and natural forage sources, are not properly managed, the grazing and other factors may lead to the increase of the plant species which affect to reduce the animal production and may cause the deterioration of the natural vegetation cover. In this study, many rangeland and pasture plants which are located in the Mediterranean climate zone and have different secondary metabolites have been examined and the positive and toxic effects on livestock health have been discussed. In addition, the proper management systems in the rangeland and pasture areas where these species are seen have been described and accor...

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