Biomedical Engineering Reference
In-Depth Information
5.1.3
Silage Feed
The preservation technology that makes silage maintains the quality of green feed
stably for a long time by fermentation in a sealed condition [
24
]. The raw materials
of silage can be the whole plant or a part of the plant. This feed can effectively
reserve the nutrients of the green plant to ensure freshness, palatability, and high
digestibility, which is a comparatively good feed, particularly for ruminants such as
cattle and sheep.
The principle of silage preparation is to convert the sugars in the raw materials
into lactic acid to form an acid environment by anaerobic fermentation of lactic acid
bacteria in the raw materials and the air. The acid environment will decrease the pH
of silage materials to below 4.2 and inhibit and kill various harmful microorganisms
to save the feed for long-term usage. To meet the requirements of lactic acid bacteria
fermentation, certain soluble sugars are needed in addition to the guarantee of
anaerobic and water conditions [
25
].
In the process of creating silage, because of the effects of raw material, weather,
and other factors, it is difficult to ensure the quality of silage and the successful
silage process. To accelerate the silage rate and improve the quality and utilization
of silage, the addition of appropriate additives is an extensive and effective method
for modulation of silage feed [
26
].
Types of silage additives are divided into four categories: fermentation inhibitors,
nutritional additives, fermentation accelerants, and inhibitors of corruption:
①
Fermentation inhibitors, such as formic acid, formaldehyde, and so on, partly
or fully inhibit the growth of microorganisms to reduce the loss of nutrition in
the fermentation process when the silage fermentation is carried out to a certain
extent.
Nutritional additives, such as urea and minerals, mainly improve the
nutritional value of silage and generally do not show any promoting function
for fermentation.
②
Fermentation accelerants, such as lactic acid bacteria, sugars
(soluble carbohydrates), and enzyme preparation, produce more lactic acid to
speed up the silage process by enhancing the activities of the lactic acid bacteria.
④
③
Inhibitors of corruption, such as propionic acid and formate, prevent silage
corruption by secondary fermentation (bacteria refermentation) [
13
,
26
,
27
].
5.1.4
Microbial Silage Feed
Silage, which belongs to natural fermentation using microorganisms in nature,
has strict demands on time and environment as the operating season is short and
cannot effectively control the microorganisms in nature. Therefore, there are certain
restrictions to popularize silage. Compared with silage, microbial fermentation is
directional fermentation. The active microbial strains are added in the fermentation
process to become the dominant strains in the early stage of fermentation and inhibit
the growth of harmful microorganisms to stabilize feed quality [
28
].
