Chemical and biological additives in forage conservation
1991
Spoelstra, S.F. (Research Inst. for Livestock Feeding and Nutrition, Lelystad (Netherlands))
Improvement of silage technology by the introduction of better machinery and silos (including plastic sheets for covering has made ensiling the main method for forage conservation. It has been estimated that in West-Europe 60 % (equivalent to 77 Mt dry matter) of the forage preserved for winter feed is ensiled. This concerns grass and maize and relatively small amounts of other crops including beet tops and sugar beet pulp. With the demand for higher efficiency in animal production, the extent of nutrient losses caused by fermentation, aerobic deterioration and effluent production were recognised as problems. Recently introduced production limits for dairying and, in some countries, environmental legislation indirectly restricting the type and amounts of nutrients used for livestock production underline the necessity to feed high quality silages. Through a well preserved silage will normally show better animal performance than a less well preserved silage, there is still a wish for further improvements of silages even, if possible, over that of the original crop. The use of aldehydes to protect protein from rumen degradation can be considered as an attempt in this direction. Silage additives have primarily been regarded as products to improve lactic acid fermentation. Often the goal of using an additive has been formulated as simple as "preventing a butyric acid fermentation". As a consequence, the efficacy of additives has been judged by effects on typical fermentation parameters as pH, ammonia, amounts and composition of organic acids. This orientation on fermentation is also reflected in the traditional division of additives in fermentation inhibitors, including acids and formaldehyde and fermentation stimulants comprising substrates for lactic acid bacteria, enzymes and inoculants.
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