Silage forages
Silage is a method of preservation in the absence of air and in the presence of a predominant lactic fermentation of green forages (corn during the milk-ripe growing season for early varieties or in the ripening stage for late varieties, legumes, meslins), may constitute a method of improving the quality of coarse forages (corn cobs).
The advantages of using silage forages consist in reducing the nutrient losses (10-15%), ensuring high milk productions, mitigating the toxic effects of some plants, forage storage under optimum conditions over a long period and their likeness to mechanized distribution.
Plant silage technology. The harvesting of plants is done in a mechanized way, the machines being preferred, which, along with cutting, also runs the hay chopping. The pace should be linked with the transport and silage possibilities. The transport of the forage at the silage site is provided with means for automatic unloading and in a sufficient number, for filling the silage in short time. A silage of 500-1000 tones must completed in 5-10 days. Once unloaded, the minced mass is leveled in layers of 30-35 cm thick and it is tamped down continuously, from the first to the last layer, with crawler tractors or wheels equipped with double tires and leveling blade. At the top, the silage is left with ridge, to facilitate the water flow, after which it is covered with different materials (plastic film, straw bales etc.) to maintain anaerobic conditions achieved by compaction.
Method : Silage methods.
a) hot silaging is rarely used in practice, because losses in digestible nutrients reach 20-30%. The high temperature (> 30 °) favors the development of butyric bacteria fermentation and the organoleptic characteristics of the forage gets worse.
b) cold silaging (regular) is practiced for plants with a water content more than 70%, rich in soluble carbohydrates, but also for plants whose silaging is difficult. The temperature in the silage mass rises to 25-30oC and the oxidation losses are much lower compared to hot silaging (about 12-17%).
c) silaging by the use of additives to increase the content of fermentable sugars, or to lower the pH of the silage mass has pH values below 4.5.
The products that can be used can be divided into three groups:
forages with role in fermentation facilitation – corn grits, barley, oats; chopped hay or chaff in proportion of 10-30% of the mass to be silaged, to reduce humidity; dried molasses in an amount of 20-40 kg / t of fresh material, for legume silaging without fading in advance; fermentable carbohydrate-rich grasses, all for silaging legumes, in the proportion of 1.5-2 parts grasses at one part of well-chopped vegetables;
chemical additives - formic acid, metabisulfite, formaldehyde, hydrochloric acid, sulfuric acid, urea, ammonia, as well as some preparations with bacteriostatic action on the organisms that cause butyric fermentation;
biological additives - cultures of bacteria, in particular lactic bacteria and enzymes (cellulases and hemicellulases).
d) silaging plants with low humidity is a modern method applied to silaging protein-rich forages and with a lower content of fermentable carbohydrates, causing little loss of nutrients. The method is based on reducing the moisture by wilting. Depending on the silaging moisture of the plant, it can be performed the following types of forage: semi-silage (55-65% moisture) and semi-hay (45-55% moisture).
Good quality silaged forage has to have a color close to the one of the plants from which it belonged, a pleasant smell, sweet-sour taste, flavored, a structure close to the original plant, with the pH between 3.8-4.5, total acid quantity between 1.5-2.5%, of which at least 2/3 to be lactic acid, acetic acid up to 1/3, and butyric acid to lack. For a silage and semi-silage of good quality, the content of lactic acid should be between 6-11% of the dry matter.
In the silaging process occur important nutrient losses caused by very different causes, such as:
1. losses in the field, as a result of shaking the leaves and the biological processes that take place after the plant harvest. As long as the plants are left on the field, these losses are greater. These losses are almost zero when silaging directly;
2. losses during storage are metabolic losses of about 8-10% from the dry matter due to respiratory activity of plants and due to the fermentation of non-membrane carbohydrates;
3. distribution losses, due to uncovering the silages, plants coming in contact with air and impairment of the surface layer. These losses are higher if, with the surface on contact with the silage mass with air is higher and the coverage done improperly;
4. fermentation losses, caused by biochemical processes that occur during silaging. The size of these losses is closely related to the norms that are imposed during silaging. At the underlying silage process is the formation and accumulation of lactic acid. This is formed after the fermentation of soluble carbohydrates from plants, under the action of lactic acid bacteria which multiply extremely fast, when they meet favorable conditions. The greater the content of lactic acid, the pH value gets reduced. In a stable forage silage, of good quality, dominated by lactic acid, the pH value is up to 4.2. At lower pH values, the lactic acid accumulated in larger amounts acts as a preservative, and the proteolytic activity of bacteria is inhibited. When the silaged material has a high water content, more than 70% and a high pH, bacteria of the genus Clostridium multiply, which oxidize the lactic acid and amino acids, resulting butyric acid, ammonia and various amines (putrescine, histamine, cadaverine, etc.) which greatly devalues the quality of the silage, leading to its complete degradation.
Immediately after silaging, the temperature rises as a result of breathing processes. The higher the plant respiration is more intense and longer lasting, the nutrient losses are higher because through respiration are oxidized soluble carbohydrates and therefore occurs a decrease of the lactic acid amount.
If the silage temperature is maintained for 15-20 days at values up to 30-40°C, normal fermentation occurs and it is stimulated the emergence of biochemical processes capable of transforming a part of the carbohydrates in new substances, of aldehydes nature, which give to the forage – silage pleasant aroma. If the temperature exceeds 40°C, significant losses of nutrients and reduced digestibility occur. When the temperature increases greatly, it is possible to take place even the phenomenon of "self-ignition" of the forage-silage;
5. losses through the juice that drips from the silage, which contains saccharoses, nitrogenous soluble substances, mineral salts. These losses can be very low when the technological process was well conducted.
