Silage
Any plant material that has been fermented or “pickled” in a silo/bale is referred to as silage. A silo, on the other hand, is any storage structure used to keep green, moist fodder. The main purpose of silage preparation is to preserve green fodder during the time of adequate availability, for usage during the lean season and to maximise the retention of natural nutrients in the fodder crop during the preservation process.
Ensilage
Ensilage, often known as ensiling, is a method of conserving green fodder for use as animal feed later. Ensilage’s principles are well-known. The primary goal is to create anaerobic environment in which natural fermentation can occur. This is accomplished by compacting and consolidating the material, as well as sealing the silo to prevent air re-entry. Respiratory enzymes quickly remove air that has been trapped in the herbage. Conversely, aerobic microbial activity happens when oxygen is in touch with herbage for a prolonged period of time with development yeast and mould. As a result, the fodder degrades into a worthless, unpalatable and often harmful product. Improved compaction and fermentation of silage come from finer chopping of plant material. As a result, the palatability and intake of silage improves. The second goal is to prevent the multiplication of undesirable microbes such as Clostridia and Enterobacteria. Clostridia can be found in the form of spores on crops and in the soil. Clostridia multiply in anaerobic surroundings, producing butyric acid and breaking down amino acids, resulting in a foul-tasting silage as well as a reduced nutritional value. Enterobacteria are also capable of degrading amino acids. Lactic acid production can arrest growth of clostridia and enterobacteria. Lactic acid bacteria are naturally found on harvested crops and ferment available carbohydrates such as glucose and fructose to produce lactic acid. The lactic acid produced enhances hydrogen ion concentrations and undissociated acids to a level that inhibits unwanted organisms. The moisture content and temperature of the silage influence the pH at which clostridia and enterobacteria cannot grow. Lower the pH, wetter is the substance. A pH little below 5.0 inhibits the development of most acid-tolerant clostridia provided the dry matter content should be more than 15%. Clostridia are extremely water-sensitive organisms that require damp circumstances to thrive. Clostridia growth can be slowed by wilting of the fodder before ensiling to reduce moisture content. Lactic acid bacteria can dominate the fermentation of high dry matter crops due to their strong tolerance to low moisture conditions.
The first few days of ensiling are crucial which decides the success or failure of fermentation. Unwanted microorganisms, primarily enterobacteria, clostridia, and yeasts will be able to compete for nutrition if the pH is not dropped soon enough. This will make it more difficult to obtain a steady silage. Lactic acid bacteria will rapidly acidify the environment under favourable conditions to the point where spoilage organisms will be unable to thrive, resulting in a stable silage.
Silage Additives
For many years, researchers have investigated for additives to improve the nutritional value of silages and to eliminate some of the undesirable events associated with the ensiling process. Silage additives are added to the forage or crop during the ensiling process to improve the ensiling process, reduce nutritional losses, reduce aerobic deterioration at feed out, improve hygienic quality of the silage, limit secondary fermentation, improve aerobic stability, increase the nutritive value of the silage, and as a result increase animal production and give the livestock raiser a good ROI – Return on Investment.
Types of Silage Additives/Inoculants:
1) Fermentation stimulants:
a) Inoculant microbes e.g., Lactic acid bacteria (LAB)
b) Enzymes viz. Cellulases, Hemicellulases, Amylases
c) Fermentable carbohydrates & Sugar sources such as Molasses, sucrose, glucose, citrus pulp, pineapple pulp, sugar beet pulp
2) Fermentation inhibitors:
a) Organic acid and their salts viz. Acids and organic acid salts such as Mineral acids (e.g., formic acid, acetic acid, lactic acid, acrylic acid, calcium formate, propionic acid, propionates)
b) Other chemical inhibitors such as Formaldehyde, sodium nitrite, sodium metabisulphite
3) Aerobic spoilage inhibitors:
Propionic acid, propionates, acetic acid, caproic acid
4) Nutrients
Urea, ammonia, grain, minerals
5) Absorbents
Grain, straw, bentonite, sugar beet pulp, polyacrylamide
Biological Additives
Microbial inoculants and enzyme preparations are natural ingredients that are safe to handle, non-corrosive to machinery, do not pollute the environment and their usage has increased rapidly in recent years. Bacterial inoculants have perhaps gained more attention from researchers and livestock producers than any other aspect of silage management.
- Microbial Inoculants
Organisms
Inoculants are applied to silage to control the epiphytic bacteria population on plants that produce DM losses due to poor sugar fermentation. The two main types of microbial inoculants are 1) homofermentative and 2) heterofermentative.
Lactobacillus plantarum, Pediococcus, and Lactococcus species are homofermentative inoculants. They induce a fast fermentation that produces mostly lactic acid and quickly lowers the pH to 4, inhibiting further degradation of the crop’s sugar and protein.
Lactobacillus buchneri and Lactobacillus brevis are microorganisms belong to heterofermentative inoculants. They create a mixture of lactic and acetic acid, which causes fermentation to be slower than with homofermentative inoculants. They’re required to prevent yeast and mould from initiating the aerobic process.
- Enzyme Additives
The method of treating forages with enzymes increases digestibility through several processes, including direct hydrolysis, improved palatability, changes in intestinal viscosity, and changes in digestive site. Cellulase and Hemicellulase are enzymes that break down cell walls into sugars. The sugars generated by the enzymes facilitate the development of silage microorganisms, while fibre degrading enzymes can also improve fodder digestibility. Low-lignin feedstuffs, such as cereal silages and immature, cool-season grasses, are the best candidates for these enzymes. Fibre-digesting enzymes have been found to be successful in lowering the fibre content of grass and alfalfa crops ensiled at 60 to 70 percent moisture, with grasses having the highest beneficial effect.
Enzymes require optimal conditions of pH and temperature for their action. For instance, most cellulase enzymes require a pH of 4.5 and a temperature of 50°C. Enzyme activity is influenced by surface area, binding sites, moisture level, and plant proteases.
| Feed Ingredients and By-Products as Additives | Effect in fermentation | |
| 1. | Grain | While adding grain to corn silage isn’t beneficial, doing so with hay crop silage offers advantages. Adding grain to hay crop silage boosts its energy level. For better results, grain should be broken or rolled before ensiling. |
| 2. | Molasses | Cane molasses (75 percent DM) has been frequently utilised to give quick fermentable carbohydrate for the ensilage of tropical herbages, with up to 10% w/w inclusion levels. Because of its viscosity, it is difficult to apply and should be diluted with a little amount of warm water to prevent seepage. |
| 3. | Starch Sources | Its usage depends on the amount of starch that is accessible as a substrate for lactic acid bacteria. |
| 4. | Citrus Pulp | Fresh citrus peels have been added to the ensilage of Napier grass at concentrations up to 50%, enhancing fermentation quality as evaluated by low pH, low butyric acid content, and appropriate lactic acid generation. |
| Acids | Effect in fermentation | |
| 1. | Formic Acid and/or Formaldehyde Treatments | Commercial formic acid (85 %) has long been used to ensilage unwilted grasses but owing to its dangers in handling and application as well as its caustic nature it is replaced with biological additives. |
| 2. | Propionic Acid | Propionic acid has the most anti-mycotic effect among the short-chain fatty acids. It is not as strong as formic or mineral acids but is safe for use in silage. Propionic acid has been proven to reduce moulds and yeasts that cause silage to deteriorate aerobically. |
| 3. | Sodium Diacetate | Acetic acid and sodium salt combination has comparable effects to propionic acid and is very good in preventing top spoiling. |
| Nutrient Additives | Effect in fermentation | |
| 1. | Ammonia and Urea | With variable degrees of efficacy, ammonia has been used to treat corn silage, tiny cereal grain silage, and high moisture corn, but not alfalfa silage. |
| 2. | Minerals | At the time of ensiling, minerals often have little effect on fermentation. Adding minerals at the time of ensiling will improve the nutritional profile of the silage. |
Conclusion:
Improved ensiling process requires Homofermentative as well as Heterofermentative bacterial inoculation. In which Heterofermentative Lactobacillus buchneri improve aerobic stability of silages by reducing the growth of yeasts. Homofermentative Lactobacillus plantarum, Pediococcus acidilactici and Enterococcus faecium induce a fast fermentation that produces mostly lactic acid and maintain pH between 3.5-4.2. Enterococcus faecium is effective in the reduction of E. coli and enterobacteriae in the silage. Cellulase and Hemicellulase are enzymes that break down cell walls into sugars that make more availability of carbohydrates for ensiling process. The net effect is that silages inoculation with Bacterial inoculants are more resistant to aerobic condition at feed out (exposure to air) and enzyme inoculants improve digestibility of the silage as compared to untreated silages.
Dr. Love Ahuja
Technical Manager- Neospark Drugs and Chemical Pvt Ltd.