After nearly 100 years of scientific research on silage, researchers and dairy farmers have long realized that successful fermentation can greatly extend the preservation time of forages and grains.
Preservation is so effective that silage can retain its nutritional value for decades. In fact, I have personally witnessed the silage stored in 1988, and its quality is almost the same as that of many silages in 2018.
The reason why silage is so stable is that an anaerobic environment is formed during fermentation, and lactic acid bacteria convert sugar into lactic acid and acetic acid. The fermentation process depends on temperature and humidity. Successful fermentation will inhibit the growth and reproduction of spoilage yeast, mold and other harmful bacteria.
Just as fermented bread requires a suitable temperature and humidity environment, silage also requires a certain amount of heat to be fermented, and the critical temperature for fermentation is between about 4°C and 10°C. When the microorganisms start to work and ferment, they digest carbohydrates to produce acid. At the same time, with the production of heat, the fermentation process continues until the pH value is lower than 4-4.5, and the silage will stabilize. In most years, sufficient temperature is not a problem, because forage crops are harvested and stored in spring and summer, and the temperature in autumn is much higher than the freezing point. However, due to the delayed planting or insufficient effective accumulated temperature during the growing season, the harvesting period will be delayed to late autumn, and the ambient temperature may not be enough to start the fermentation process of the silage. In these cases, the quality index of silage may be different from the previous empirical data, and there are several related reasons.
The stability of feed quality is the primary goal, and silage will affect the digestibility of starch in the rumen and the entire digestive tract. The silage fermentation process destroys the gliadin that wraps cornstarch. This protein is the same as the protein in the paper cup and is insoluble in water. Therefore, if the grains are not soluble in water, rumen microorganisms cannot degrade these starches. The silage fermentation can decompose these proteins and release the starch in the corn kernels, which helps the rumen digestion, thereby greatly improving the feed quality.
In addition to starch digestibility, silage can also remove a large amount of spoilage yeast, mold and other harmful bacteria in the feed. In the United States, these effects have been verified. Environmental conditions, farming methods and rainfall are all factors that affect the quality of silage. But remember, if the silage fermentation process cannot go on, then some harmful microorganisms in the feed may continue to exist. If the feed contains some dormant harmful microorganisms, fermentation cannot be eliminated, or worse, unfermented crops are precisely the most beneficial growth environment for these microorganisms. When these feeds are used in the diet, harmful microorganisms may wake up and grow and multiply in the diet.
In addition to the content discussed in this article, silage may also face other challenges, such as low protein and mineral content, high mycotoxin load, or soil contamination, etc.