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Processing and Value
addition
Forage Conservation
Silage and Hay making : Forage
preservation is an important technique in intensive dairy management wherein it
ensures adequate supply of plant nutrients during the lean season. Preservation
means storing of green forage available during the lush season to feed the animals
during the lean periods. Plants grow well with the onset of monsoon when moisture
and temperature are not the limiting factors. It is important that all necessary
action be initiated during this season to preserve surplus fodder.
There are two methods of forage preservation, which can be adopted by the farmers
namely Silage and Hay.
In one method the forage preservation consists of chaffing of green forage and storing
in the specially constructed underground or above ground structures ensuring that
no air or moisture enters these structures. The green forage thus stored ferments
under anaerobic conditions without appreciable loss to the nutritive value of the
material preserved. The acids formed during the process of fermentation act as preservatives.
The product thus obtained is termed ‘silage’.
The other method consists of harvesting at appropriate stage of growth, and drying
to a safe level of around 15 to 16% moisture content without much bleaching, wetting
or shattering of leaves. The forage preserved in this manner is called ‘Hay’.
Silage
Green forage in succulent form having a high moisture content preserved under controlled
fermentation conditions is called silage. Ensilage is the name given to the process,
and the container or the structures used for storing the forage crops is called
the silo. Preservation is dependent upon the fermentation of soluble carbohydrates
present in the plant material, into lactic acid resulting in a lowering of pH to
within the range of 3.8-4.2. Material of this type is described as ‘well preserved
silage’ and normally has a lactic acid content within the range of 8-12% of the
dry matter. Success in achieving a lactic acid concentration of this level depends
upon many factors, but basically upon having an adequate supply of soluble carbohydrates,
and achieving and maintaining anaerobic conditions. Silage of pH about 4 will normally
remain stable as long as the mass is kept under anaerobic conditions. However, if
rain is allowed to enter the silage or if lactic acid concentration is inadequate,
a secondary clostridial fermentation is likely to occur. Here the lactic acid is
broken down to butyric acid and the aminoacids to ammonia, organic acids, amines
and CO2, which are not desirable. If the material comes in contact with
air, organic fermentation occurs leading to over heating resulting in a blackish
form of mass, which is referred to as ‘mouldy silage’. This is often noticed in
the surface and sides of silos. Such damaged materials should not be given to animals
as it may contain nitrogenous decomposition products, which are toxic.
Types of soil
The basic principle involved in these structures is to accommodate the maximum quantity
of forage in minimum space by avoiding the entry of air and water as far as possible
for proper fermentation of the material. The size of silos can be determined on
the basis of the quantity of forage material to be ensiled, and the number of silos
depends mainly on the number of animals to be fed and period of feeding. The type
of silo depends upon the climatic conditions prevailing in the area.
Silage generally gets ready for feeding in about six to eight weeks time and can
be preserved for 2 to 3 years provided the material does not come in contact with
air or moisture. '
The best quality silage has a pH range from 3.8 to 4.2 and is greenish yellow in
colour. The materials should not stick to each other. The brown colour of silage
is due to a pigment, phaeophytin that is a magnesium free derivative of chlorophyll.
The smell would be fruity type.
While opening the pits for feeding the animals, the pit should not be fully exposed
to air. Required quantity could be removed and fed to the animals. 10 to 15 kg/day/adult
animal is the recommended quantity of silage that can be fed. Preferably, silage
should be fed as the first feed of the day as forced feeding (when it is hungry)
could increase the intake.
Hay
The commonest method of conserving green crops is by hay making, the success of
which depends up on having a period of fine favourable weather.
The aim of haymaking is to reduce the moisture content of the green crop to a level
low enough to inhibit the action of plant and microbial enzymes. The moisture content
of green crop depends on many factors, but may range from about 65 to 85%, tending
to fall as the plant matures. In order to store a green crop satisfactory in a stack
or bale, the moisture content must be reduced to 15-16%. The custom of cutting the
crop in a mature state when the moisture content is at its lowest is a sensible
procedure for rapid drying and maximum yield, but unfortunately the more mature
the herbage, the poorer is the nutritive value.
Paddy Straw
The vegetative portion of paddy plant after harvesting the grain is dried and used
as roughage feed for cattle. It is high in crude fibre, low in protein and low in
energy value. Paddy straw forms the staple roughage of the cattle of Kerala. Well
cured straw will have golden yellow colour and has a TDN value of 40 to 44%. Treating
the material with urea at the rate of 4 kg per 100 kg dry straw at 50 to 55% moisture
level and keeping the material under anaerobic condition for atleast 6 weeks can
improve the nutritive value of paddy straw.
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