Transcript Silage Production

Applications of
Biotechnological Processes
Silage Production
Cattle and sheep are dependant upon
grass for food. During winter, farmers need
to provide an alternative food source.
In the past, livestock were fed hay (dried
grass), but this has a low nutritional value.
Today, cattle are fed grass which has been
fermented (silage), as it retains it
nutritional value.
Silage is light brown- yellow in colour, has
little smell and can be kept stable for many
years.
Procedure
Silage is made through the
fermentation of grass. The process is
called ensilage.
Grass is cut and allowed to wilt for
several hours.
 It is then transferred
into “silos”
or black polythene
bags/bales.
 Anaerobic conditions
are generated in the
sealed silo (any oxygen is
used up by respiring,
cut grass).
A cocktail of bacterial species and
hydrolytic enzymes are added e.g.
pectinases and cellulases
Cellulases and pectinases digest the
grass cell walls to release nutrients from
the cells that bacteria can utilise
A mixture of bacteria are used as no single
species is suited to the conditions that
occur throughout the fermentation
process.
Lactobacillus and Enterococcus species
are usually used.
 Enterococcus requires aerobic conditions and a
higher pH to work, so it is better suited to the
early stages of fermentation.
 Through the metabolic activity of Enterococcus,
conditions in the silo/plastic bag will become
more acidic (< pH5) and anaerobic.
 In these conditions the Lactobacillus will take
over the fermentation process
The temperature also rises from around
5oC to 50oC due to the microbial activity.
The rise in temperature further aids the
fermentation process.
Spoilage
Spoilage microorganisms e.g. Clostridium
and Enterobacillus, could potentially
reduce the quality of the silage, making it
unpalatable to livestock.
However, the acidic and anaerobic
conditions created through the
fermentation process inhibit the action of
these microbes.
Past Paper Questions
2006 Q4
2004 Q1(i)