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Agriculture > Forage Crops

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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