Rumen Fungi - Their Roles and Potential for Manipulation
نویسنده
چکیده
Large populations of obligately anaerobic fungi colonise plant fragments in the rumen of cattle and sheep on fibrous diets. Highest numbers are present on stem fragments and the fungi are found associated mainly with the lignified tissues that remain in the rumen for prolonged periods. Fungal populations are highest in animals receiving high-fibre diets and are absent from the rumen contents of animal receiving soft leafy forages, presumably due to the short retention-times of the latter feedstuffs. The major route of fungal invasion is via areas of damaged epidermis that permit access to internal plant tissues. The anaerobic fungi possess the range of glycosidases required for digestion of cellulose and hemicellulose to simple sugars and the products of the resultant fermentations include acetate, lactate, ethanol, formate, carbon dioxide and hydrogen. The properties of the fungi together with the extent of colonisation and growth on fibrous plant fragments suggests a significant role in cellulose digestion in the rumen. However the magnitude of the fungal contribution to rumen fermentation remains to be quantified and awaits development of a reliable method for determination of the fungal mass in the rumen. Despite this gap in our knowlege of the fungi, their properties, including their positive association with high-fibre diets, bring them to attention as possible candidates that might be manipulated to produce improved utilisation of highfibre forages.
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Rumen Manipulation to Improve Animal Productivity
Anaerobic rumen microorganisms mainly bacteria, protozoa and fungi degrade ligno-cellulosic feeds consumed by the ruminants. The ruminants in developing countries are predominantly maintained on low grade roughage and grazing on degraded range land resulting in their poor nutrient utilization and productivity. Hence, manipulation of rumen fermentation was tried during last two decades to optimi...
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