BIOLOGY Volume 2 - A Guide to General Biology - 2004

12. MICROBIOLOGY AND BIOTECHNOLOGY

12.13. Agriculture

12.13.2. Silage

Silage production is a traditional anaerobic Fermentation process widely used on farms to preserve the Nutritional Value of grass for feeding livestock, particularly dairy cattle, during the winter months. Grass naturally carries a population of lactic acid Bacteria, such as Lactobacillus. Once mown, the grass is chopped and packed into a large silo or, more recently, baled and wrapped in heavy-duty black plastic. The bacteria metabolize the natural sugars present in the grass—such as glucose, fructose, and sucrose—as an energy source for Anaerobic Respiration (traditional fermentation), converting them into lactic acid. Although lactic acid is the primary product, fermentation also yields Other Compounds that give silage its characteristic taste and aroma. As fermentation proceeds, the pH drops to around 4. This acidic environment inhibits the growth of putrefactive bacteria that would otherwise spoil the grass completely and destroy its nutritional value. Temperatures can rise significantly during fermentation, requiring the bacteria to be thermotolerant. Contamination by Listeria bacteria must be strictly avoided, as it can cause Listeriosis, leading to Sepsis or stillbirths in farm animals. Such contamination is prevented by ensuring vigorous fermentation and maintaining a pH below 5.5.

Today, the reliability and quality of silage production have significantly improved through The Use of commercial inoculants containing fast-growing lactic acid bacteria. These are supplied as powders or liquids to treat freshly harvested grass. At its Billingham fermentation plant, ICI manufactures three such products: Ecosyl, Ecohay, and Ecobale. Evidence indicates that using these inoculants enhances animal productivity. This is likely due, on the one hand, to a more efficient conversion of sugars into lactic acid and, on the other hand, to improved palatability, which encourages livestock to consume larger quantities of silage.